Biology

2025

Jump to: 2024, 2023, 2022

15 pages, 1381 KiB

Open AccessReview

How Melatonin Affects Plant Growth and the Associated Microbiota

by Elisa Gamalero and Bernard R. Glick

Biology 2025, 14(4), 371; https://doi.org/10.3390/biology14040371 - 3 Apr 2025

Viewed by 208

Abstract

Melatonin is found in all classes of living organisms. In particular, in plants melatonin acts as an antioxidant that helps plants deal with both biotic and abiotic stress. In plants, melatonin improves seed germination, fruit ripening, photosynthesis, biomass production, circadian rhythm, membrane integrity, [...] Read more.

Melatonin is found in all classes of living organisms. In particular, in plants melatonin acts as an antioxidant that helps plants deal with both biotic and abiotic stress. In plants, melatonin improves seed germination, fruit ripening, photosynthesis, biomass production, circadian rhythm, membrane integrity, root development, leaf senescence, osmoregulation, and stress modulation. Melatonin concentrations vary enormously in different plants, different plant growth stages, different plant organs, and both the season and time of day that a plant is harvested. In addition, melatonin promotes root growth and development, prevents leaf senescence, promotes flowering and fruit ripening, promotes lateral root formation, stimulates gene expression of enzymes involved in photosynthesis, and protects plants from phytopathogen attack. Moreover, melatonin produced by soil bacteria can affect plant tolerance and health; in turn, melatonin synthesized by plants can influence the soil and rhizosphere microbiome. Finally, very recent literature indicates that melatonin can directly and positively affect the functioning of other soil bacteria. Full article

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9 pages, 1586 KiB

Open AccessCommunication

Investigation and Identification of Fungal Diseases of Aloe barbadensis in China

by Guohui Zhang, Qingjia Wan, Xiangyang Li and Jie Deng

Biology 2025, 14(1), 89; https://doi.org/10.3390/biology14010089 - 17 Jan 2025

Viewed by 686

Abstract

The Aloe barbadensis industry plays an important role in the economic development of Yuanjiang county of Yuxi city in Yunnan province, China. In order to reduce the harm of diseases and ensure the quality of products, the occurrence of A. barbadensis was investigated. [...] Read more.

The Aloe barbadensis industry plays an important role in the economic development of Yuanjiang county of Yuxi city in Yunnan province, China. In order to reduce the harm of diseases and ensure the quality of products, the occurrence of A. barbadensis was investigated. The pathogenic fungi of wild and cultivated species of A. barbadensis were isolated by a tissue separation method, and DNA sequencing was carried out by using the sequence analysis of the ribosomal rDNA-ITS region, and the pathogenic fungi were classified and identified by finally combining morphological observations. The results showed that the main fungal diseases were root rot and leaf rot disease caused by Fusarium oxysporum, leaf spot disease caused by Curvularia lunata, anthracnose caused by Colletotrichum boninense, and brown spot disease caused by Alternaria alternata on A. barbadensis. Full article

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2024

Jump to: 2025, 2023, 2022

16 pages, 4059 KiB

Open AccessArticle

Rhizobacteria Isolated from Amazonian Soils Reduce the Effects of Water Stress on the Growth of Açaí (Euterpe oleracea Mart.) Palm Seedlings

by Suania Maria do Nascimento Sousa, Josinete Torres Garcias, Marceli Ruani De Oliveira Farias, Allana Laís Alves Lima, Rosiane do Socorro dos Reis de Sousa, Hellen Kempfer Philippsen, Lucimar Di Paula dos Santos Madeira, Herve Rogez and Joana Montezano Marques

Biology 2024, 13(10), 757; https://doi.org/10.3390/biology13100757 - 24 Sep 2024

Viewed by 1425

Abstract

Euterpe oleracea Mart., also known for its fruit açaí, is a palm native to the Amazon region. The state of Pará, Brazil, accounts for over 90% of açaí production. Demand for the fruit in national and international markets is increasing; however, climate change [...] Read more.

Euterpe oleracea Mart., also known for its fruit açaí, is a palm native to the Amazon region. The state of Pará, Brazil, accounts for over 90% of açaí production. Demand for the fruit in national and international markets is increasing; however, climate change and diseases such as anthracnose, caused by the fungus Colletotrichum sp., lead to decreased production. To meet demand, measures such as expanding cultivation in upland areas are often adopted, requiring substantial economic investments, particularly in irrigation. Therefore, the aim of this study was to evaluate the potential of açaí rhizobacteria in promoting plant growth (PGPR). Rhizospheric soil samples from floodplain and upland açaí plantations were collected during rainy and dry seasons. Bacterial strains were isolated using the serial dilution method, and subsequent assays evaluated their ability to promote plant growth. Soil analyses indicated that the sampling period influenced the physicochemical properties of both areas, with increases observed during winter for most soil components like organic matter and C/N ratio. A total of 177 bacterial strains were isolated from rhizospheres of açaí trees cultivated in floodplain and upland areas across dry and rainy seasons. Among these strains, 24% produced IAA, 18% synthesized ACC deaminase, 11% mineralized organic phosphate, and 9% solubilized inorganic phosphate, among other characteristics. Interestingly, 88% inhibited the growth of phytopathogenic fungi of the genera Curvularia and Colletotrichum. Analysis under simulated water stress using Polyethylene Glycol 6000 revealed that 23% of the strains exhibited tolerance. Two strains were identified as Bacillus proteolyticus (PP218346) and Priestia aryabhattai (PP218347). Inoculation with these strains increased the speed and percentage of açaí seed germination. When inoculated in consortium, 85% of seeds germinated under severe stress, compared to only 10% in the control treatment. Therefore, these bacteria show potential for use as biofertilizers, enhancing the initial development of açaí plants and contributing to sustainable agricultural practices. Full article

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16 pages, 2613 KiB

Open AccessArticle

Enhancing Maize Stress Tolerance and Productivity through Synergistic Application of Bacillus velezensis A6 and Lamiales Plant Extract, Biostimulants Suitable for Organic Farming

by María Peñas-Corte, Paula R. Bouzas, Juan Nieto del Río, Maximino Manzanera, Adoración Barros-Rodríguez and José R. Fernández-Navarro

Biology 2024, 13(9), 718; https://doi.org/10.3390/biology13090718 - 12 Sep 2024

Cited by 3 | Viewed by 1538

Abstract

Maize, a globally significant cereal, is increasingly cultivated under challenging environmental conditions, necessitating innovations in sustainable agriculture. This study evaluates the synergistic effects of a novel technique combining a Bacillus velezensis A6 strain with a plant extract from the Lamiales order on maize [...] Read more.

Maize, a globally significant cereal, is increasingly cultivated under challenging environmental conditions, necessitating innovations in sustainable agriculture. This study evaluates the synergistic effects of a novel technique combining a Bacillus velezensis A6 strain with a plant extract from the Lamiales order on maize growth and stress resilience. Employing a pilot field trial, this study was conducted on the “La Añoreta” experimental farm of the ECONATUR group, where various biostimulant treatments, including bacterial and plant extract applications, were tested against a control group. The treatments were applied during key vegetative growth stages (V10-Tenth-Leaf, VT-Tassel, R1-Silking) and monitored for effects on plant height, biomass, and fumonisin content. The results suggest that the combined treatment of Bacillus velezensis A6 and the plant extract increases maize height (32.87%) and yield (62.93%) and also reduces fumonisin concentrations, improving its resistance to stress, compared to the control and other treatments. This study highlights the potential of microbial and botanical biostimulants and its novel combination for improving crop productivity and sustainability, suggesting that such synergistic combinations could play a crucial role in enhancing agricultural resilience to environmental stresses. Full article

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27 pages, 10083 KiB

Open AccessEditor’s ChoiceArticle

Comparative Study of Bacillus-Based Plant Biofertilizers: A Proposed Index

by Adoración Barros-Rodríguez, Pamela Pacheco, María Peñas-Corte, Antonio J. Fernández-González, José F. Cobo-Díaz, Yasmira Enrique-Cruz and Maximino Manzanera

Biology 2024, 13(9), 668; https://doi.org/10.3390/biology13090668 - 28 Aug 2024

Cited by 2 | Viewed by 1630

Abstract

The market for bacteria as agricultural biofertilizers is growing rapidly, offering plant-growth stimulants; biofungicides; and, more recently, protectors against extreme environmental factors, such as drought. This abundance makes it challenging for the end user to decide on the product to use. In this [...] Read more.

The market for bacteria as agricultural biofertilizers is growing rapidly, offering plant-growth stimulants; biofungicides; and, more recently, protectors against extreme environmental factors, such as drought. This abundance makes it challenging for the end user to decide on the product to use. In this work, we describe the isolation of a strain of Bacillus velezensis (belonging to the operational group Bacillus amyloliquefaciens) for use as a plant-growth-promoting rhizobacterium, a biofungicide, and a protector against drought. To compare its effectiveness with other commercial strains of the same operational group, Bacillus amyloliquefaciens, we analyzed its ability to promote the growth of pepper plants and protect them against drought, as well as its fungicidal activity through antibiosis and antagonism tests, its ability to solubilize potassium and phosphates, and its ability to produce siderophores. Finally, we used a probit function, a type of regression analysis used to model the outcomes of analyses, to quantify the biostimulatory effectiveness of the different plant-growth-promoting rhizobacteria, developing what we have called the Agricultural Protection Against Stress Index, which allowed us to numerically compare the four commercial strains of the operational group Bacillus amyloliquefaciens, based on a Delphi method—a type of regression analysis that can be used to model a cumulative normal distribution—and integrate the results from our panel of tests into a single value. Full article

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21 pages, 2628 KiB

Open AccessArticle

The Impact of Nitrogen-Fixing Bacteria-Based Biostimulant Alone or in Combination with Commercial Inoculum on Tomato Native Rhizosphere Microbiota and Production: An Open-Field Trial

by Giorgia Novello, Elisa Bona, Martina Nasuelli, Nadia Massa, Cristina Sudiro, Daniela Cristina Campana, Susanna Gorrasi, Marie Louise Hochart, Adriano Altissimo, Francesco Vuolo and Elisa Gamalero

Biology 2024, 13(6), 400; https://doi.org/10.3390/biology13060400 - 31 May 2024

Cited by 2 | Viewed by 2206

Abstract

The agricultural sector is currently encountering significant challenges due to the effects of climate change, leading to negative consequences for crop productivity and global food security. In this context, traditional agricultural practices have been inadequate in addressing the fast-evolving challenges while maintaining environmental [...] Read more.

The agricultural sector is currently encountering significant challenges due to the effects of climate change, leading to negative consequences for crop productivity and global food security. In this context, traditional agricultural practices have been inadequate in addressing the fast-evolving challenges while maintaining environmental sustainability. A possible alternative to traditional agricultural management is represented by using beneficial micro-organisms that, once applied as bioinoculants, may enhance crop resilience and adaptability, thereby mitigating the adverse effects of environmental stressors and boosting productivity. Tomato is one of the most important crops worldwide, playing a central role in the human diet. The aim of this study was to evaluate the impact of a nitrogen-fixing bacterial-based biostimulant (Azospirillum sp., Azotobacter sp., and Rhizobium sp.) in combination or not with a commercial inoculum Micomix (Rhizoglomus irregulare, Funnelliformis mosseae, Funnelliformis caledonium, Bacillus licheniformis, and Bacillus mucilaginosus) (MYC) on the native rhizosphere communities and tomato production. Bacterial populations in the different samples were characterized using an environmental metabarcoding approach. The bioinocula effect on the native rhizosphere microbiota resulted in significant variation both in alpha and beta diversity and in a specific signature associated with the presence of biostimulants. Full article

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12 pages, 1860 KiB

Open AccessArticle

The Effects of Salinity and Genotype on the Rhizospheric Mycobiomes in Date Palm Seedlings

by Mahmoud W. Yaish, Aya Al-Busaidi, Bernard R. Glick, Talaat Ahmed and Juha M. Alatalo

Biology 2024, 13(3), 190; https://doi.org/10.3390/biology13030190 - 15 Mar 2024

Cited by 4 | Viewed by 2222

Abstract

Salinity severely affects the health and productivity of plants, with root-associated microbes, including fungi, potentially playing a crucial role in mitigating this effect and promoting plant health. This study employed metagenomics to investigate differences in the structures of the epiphyte mycobiomes in the [...] Read more.

Salinity severely affects the health and productivity of plants, with root-associated microbes, including fungi, potentially playing a crucial role in mitigating this effect and promoting plant health. This study employed metagenomics to investigate differences in the structures of the epiphyte mycobiomes in the rhizospheres of seedlings of two distinct date palm cultivars with contrasting salinity tolerances, the susceptible cultivar, ‘Zabad’, and the tolerant cultivar, ‘Umsila’. Next-generation sequencing (NGS) of the internal transcribed spacer (ITS) rRNA was utilized as a DNA barcoding tool. The sequencing of 12 mycobiome libraries yielded 905,198 raw sequences of 268,829 high-quality reads that coded for 135 unique and annotatable operational taxonomic units (OTUs). An OTU analysis revealed differences in the rhizofungal community structures between the treatments regardless of genotype, and non-metric dimensional scaling (N-MDS) analyses demonstrated distinct separations between the cultivars under saline stress. However, these differences were not detected under the control environmental conditions, i.e., no salinity. The rhizospheric fungal community included four phyla (Ascomycota, Basidiomycota, Chytridiomycota, and Mucoromycota), with differences in the abundances of Aspergillus, Clonostachys, and Fusarium genera in response to salinity, regardless of the genotype. Differential pairwise comparisons showed that Fusarium falciforme-solani and Aspergillus sydowii-versicolor increased in abundance under saline conditions, providing potential future in vitro isolation guidelines for plant growth-promoting fungi. This study highlights the intricate dynamics of the rhizosphere microbial communities in date palms and their responses to salt stress. Additionally, we found no support for the hypothesis that indigenous epiphytic fungal communities are significantly involved in salinity tolerance in date palms. Full article

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22 pages, 1641 KiB

Open AccessReview

Cellulolytic Aerobic Bacteria Isolated from Agricultural and Forest Soils: An Overview

by Angélica Bautista-Cruz, Teodulfo Aquino-Bolaños, Jessie Hernández-Canseco and Evangelina Esmeralda Quiñones-Aguilar

Biology 2024, 13(2), 102; https://doi.org/10.3390/biology13020102 - 5 Feb 2024

Cited by 9 | Viewed by 4610

Abstract

This review provides insights into cellulolytic bacteria present in global forest and agricultural soils over a period of 11 years. It delves into the study of soil-dwelling cellulolytic bacteria and the enzymes they produce, cellulases, which are crucial in both soil formation and [...] Read more.

This review provides insights into cellulolytic bacteria present in global forest and agricultural soils over a period of 11 years. It delves into the study of soil-dwelling cellulolytic bacteria and the enzymes they produce, cellulases, which are crucial in both soil formation and the carbon cycle. Forests and agricultural activities are significant contributors to the production of lignocellulosic biomass. Forest ecosystems, which are key carbon sinks, contain 20–30% cellulose in their leaf litter. Concurrently, the agricultural sector generates approximately 998 million tons of lignocellulosic waste annually. Predominant genera include Bacillus, Pseudomonas, Stenotrophomonas, and Streptomyces in forests and Bacillus, Streptomyces, Pseudomonas, and Arthrobacter in agricultural soils. Selection of cellulolytic bacteria is based on their hydrolysis ability, using artificial cellulose media and dyes like Congo red or iodine for detection. Some studies also measure cellulolytic activity in vitro. Notably, bacterial cellulose hydrolysis capability may not align with their cellulolytic enzyme production. Enzymes such as GH1, GH3, GH5, GH6, GH8, GH9, GH10, GH12, GH26, GH44, GH45, GH48, GH51, GH74, GH124, and GH148 are crucial, particularly GH48 for crystalline cellulose degradation. Conversely, bacteria with GH5 and GH9 often fail to degrade crystalline cellulose. Accurate identification of cellulolytic bacteria necessitates comprehensive genomic analysis, supplemented by additional proteomic and transcriptomic techniques. Cellulases, known for degrading cellulose, are also significant in healthcare, food, textiles, bio-washing, bleaching, paper production, ink removal, and biotechnology, emphasizing the importance of discovering novel cellulolytic strains in soil. Full article

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19 pages, 5975 KiB

Open AccessArticle

Bacterial Endophytes from Legumes Native to Arid Environments Are Promising Tools to Improve Mesorhizobium–Chickpea Symbiosis under Salinity

by Roukaya Ben Gaied, Imed Sbissi, Mohamed Tarhouni and Clarisse Brígido

Biology 2024, 13(2), 96; https://doi.org/10.3390/biology13020096 - 3 Feb 2024

Cited by 7 | Viewed by 2580

Abstract

Symbiotic nitrogen fixation is a major contributor of N in agricultural ecosystems, but the establishment of legume–rhizobium symbiosis is highly affected by soil salinity. Our interest is focused on the use of non-rhizobial endophytes to assist the symbiosis between chickpea and its microsymbiont [...] Read more.

Symbiotic nitrogen fixation is a major contributor of N in agricultural ecosystems, but the establishment of legume–rhizobium symbiosis is highly affected by soil salinity. Our interest is focused on the use of non-rhizobial endophytes to assist the symbiosis between chickpea and its microsymbiont under salinity to avoid loss of production and fertility. Our aims were (1) to investigate the impact of salinity on both symbiotic partners; including on early events of the Mesorhizobium-chickpea symbiosis, and (2) to evaluate the potential of four non-rhizobial endophytes isolated from legumes native to arid regions (Phyllobacterium salinisoli, P. ifriqiyense, Xanthomonas translucens, and Cupriavidus respiraculi) to promote chickpea growth and nodulation under salinity. Our results show a significant reduction in chickpea seed germination rate and in the microsymbiont Mesorhizobium ciceri LMS-1 growth under different levels of salinity. The composition of phenolic compounds in chickpea root exudates significantly changed when the plants were subjected to salinity, which in turn affected the nod genes expression in LMS-1. Furthermore, the LMS-1 response to root exudate stimuli was suppressed by the presence of salinity (250 mM NaCl). On the contrary, a significant upregulation of exoY and otsA genes, which are involved in exopolysaccharide and trehalose biosynthesis, respectively, was registered in salt-stressed LMS-1 cells. In addition, chickpea co-inoculation with LMS-1 along with the consortium containing two non-rhizobial bacterial endophytes, P. salinisoli and X. translucens, resulted in significant improvement of the chickpea growth and the symbiotic performance of LMS-1 under salinity. These results indicate that this non-rhizobial endophytic consortium may be an appropriate ecological and safe tool to improve chickpea growth and its adaptation to salt-degraded soils. Full article

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2023

Jump to: 2025, 2024, 2022

19 pages, 2882 KiB

Open AccessArticle

Combination of Bacillus and Low Fertigation Input Promoted the Growth and Productivity of Chinese Cabbage and Enriched Beneficial Rhizosphere Bacteria Lechevalieria

by Shi-Chang Zhang, Yu-Lu Zhang, Xiao-Jing Guo, Ming Luo, Shi-Dong Li and Rong-Jun Guo

Biology 2023, 12(8), 1130; https://doi.org/10.3390/biology12081130 - 14 Aug 2023

Cited by 4 | Viewed by 1926

Abstract

Long-term overfertilization increases soil salinity and disease occurrence and reduces crop yield. Integrated application of microbial agents with low fertigation input might be a sustainable and cost-effective strategy. Herein, the promoting effects of Bacillus velezensis B006 on the growth of Chinese cabbage under [...] Read more.

Long-term overfertilization increases soil salinity and disease occurrence and reduces crop yield. Integrated application of microbial agents with low fertigation input might be a sustainable and cost-effective strategy. Herein, the promoting effects of Bacillus velezensis B006 on the growth of Chinese cabbage under different fertigation conditions in field trials were studied and the underlying mechanisms were revealed. In comparison with normal fertigation (water potential of −30 kPa and soluble N, P, K of 29.75, 8.26, 21.48 Kg hm⁻²) without B006 application, the combination of B. velezensis B006 and reduced fertigation input (−50 kPa and N, P, K of 11.75, 3.26, 6.48 Kg hm⁻²) promoted cabbage growth and root development, restrained the occurrence of soft rot disease, and improved the yield. High-performance liquid chromatography (HPLC) analyses indicated that B006 application promoted the production of indole-3-acetic acid and salicylic acid in cabbage roots, which are closely related to plant growth. Rhizosphere microbiota analyses indicated that the combination of low fertigation input and B006 application promoted the enrichment of Streptomyces, Lechevalieria, Promicromonospora, and Aeromicrobium and the abundance of Lechevalieria was positively correlated with the root length and vitality. This suggested that the integrated application of reduced fertigation and Bacillus is highly efficient to improve soil ecology and productivity and will benefit the sustainable development of crop cultivation in a cost-effective way. Full article

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18 pages, 2345 KiB

Open AccessReview

Ethylene, ACC, and the Plant Growth-Promoting Enzyme ACC Deaminase

by Elisa Gamalero, Guido Lingua and Bernard R. Glick

Biology 2023, 12(8), 1043; https://doi.org/10.3390/biology12081043 - 25 Jul 2023

Cited by 33 | Viewed by 4982

Abstract

Here, a brief summary of the biosynthesis of 1-aminocyclopropane-1-carboxylate (ACC) and ethylene in plants, as well as overviews of how ACC and ethylene act as signaling molecules in plants, is presented. Next, how the bacterial enzyme ACC deaminase cleaves plant-produced ACC and thereby [...] Read more.

Here, a brief summary of the biosynthesis of 1-aminocyclopropane-1-carboxylate (ACC) and ethylene in plants, as well as overviews of how ACC and ethylene act as signaling molecules in plants, is presented. Next, how the bacterial enzyme ACC deaminase cleaves plant-produced ACC and thereby decreases or prevents the ethylene or ACC modulation of plant gene expression is considered. A detailed model of ACC deaminase functioning, including the role of indoleacetic acid (IAA), is presented. Given that ACC is a signaling molecule under some circumstances, this suggests that ACC, which appears to have evolved prior to ethylene, may have been a major signaling molecule in primitive plants prior to the evolution of ethylene and ethylene signaling. Due to their involvement in stimulating ethylene production, the role of D-amino acids in plants is then considered. The enzyme D-cysteine desulfhydrase, which is structurally very similar to ACC deaminase, is briefly discussed and the possibility that ACC deaminase arose as a variant of D-cysteine desulfhydrase is suggested. Full article

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17 pages, 26306 KiB

Open AccessArticle

Plant–Microbes Interaction: Exploring the Impact of Cold-Tolerant Bacillus Strains RJGP41 and GBAC46 Volatiles on Tomato Growth Promotion through Different Mechanisms

by Abdur Rashid Khan, Qurban Ali, Muhammad Ayaz, Muhammad Saqib Bilal, Taha Majid Mahmood Sheikh, Qin Gu, Huijun Wu and Xuewen Gao

Biology 2023, 12(7), 940; https://doi.org/10.3390/biology12070940 - 30 Jun 2023

Cited by 7 | Viewed by 2467

Abstract

The interaction between plant and bacterial VOCs has been extensively studied, but the role of VOCs in growth promotion still needs to be explored. In the current study, we aim to explore the growth promotion mechanisms of cold-tolerant Bacillus strains GBAC46 and RJGP41 [...] Read more.

The interaction between plant and bacterial VOCs has been extensively studied, but the role of VOCs in growth promotion still needs to be explored. In the current study, we aim to explore the growth promotion mechanisms of cold-tolerant Bacillus strains GBAC46 and RJGP41 and the well-known PGPR strain FZB42 and their VOCs on tomato plants. The result showed that the activity of phytohormone (IAA) production was greatly improved in GBAC46 and RJGP41 as compared to FZB42 strains. The in vitro and in-pot experiment results showed that the Bacillus VOCs improved plant growth traits in terms of physiological parameters as compared to the CK. The VOCs identified through gas chromatography-mass spectrometry (GC-MS) analysis, namely 2 pentanone, 3-ethyl (2P3E) from GBAC46, 1,3-cyclobutanediol,2,2,4,4-tetramethyl (CBDO) from RJGP41, and benzaldehyde (BDH) from FZB42, were used for plant growth promotion. The results of the partition plate (I-plate) and in-pot experiments showed that all the selected VOCs (2P3E, CBDO, and BDH) promoted plant growth parameters as compared to CK. Furthermore, the root morphological factors also revealed that the selected VOCs improved the root physiological traits in tomato plants. The plant defense enzymes (POD, APX, SOD, and CAT) and total protein contents were studied, and the results showed that the antioxidant enzymes and protein contents significantly increased as compared to CK. Similarly, plant growth promotion expression genes (IAA4, ARF10A, GA2OX2, CKX2, and EXP1) were significantly upregulated and the ERF gene was downregulated as compared to CK. The overall findings suggest that both Bacillus isolates and their pure VOCs positively improved plant growth promotion activities by triggering the antioxidant enzyme activity, protein contents, and relative gene expressions in tomato plants. Full article

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18 pages, 2326 KiB

Open AccessArticle

The Co-Association of Enterobacteriaceae and Pseudomonas with Specific Resistant Cucumber against Fusarium Wilt Disease

by Yu-Lu Zhang, Xiao-Jing Guo, Xin Huang, Rong-Jun Guo, Xiao-Hong Lu, Shi-Dong Li and Hao Zhang

Biology 2023, 12(2), 143; https://doi.org/10.3390/biology12020143 - 17 Jan 2023

Cited by 8 | Viewed by 2961

Abstract

The root microbiota contributes to the plant’s defense against stresses and pathogens. However, the co-association pattern of functional bacteria that improves plant resistance has not been interpreted clearly. Using Illumina high-throughput sequencing technology, the root bacterial community profiles of six cucumber cultivars with [...] Read more.

The root microbiota contributes to the plant’s defense against stresses and pathogens. However, the co-association pattern of functional bacteria that improves plant resistance has not been interpreted clearly. Using Illumina high-throughput sequencing technology, the root bacterial community profiles of six cucumber cultivars with different resistance in response to the causative agent of cucumber Fusarium wilt (CFW), Fusarium oxysporum f. sp. cucumerinum (Foc), were analyzed. The principal coordinate analysis indicated that the interactions of the cultivars and pathogens drove the cucumber root bacterial communities (p = 0.001). The resistance-specific differential genera across the cultivars were identified, including Massilia in the resistant cultivars, unclassified Enterobacteriaceae in resistant CL11 and JY409, Pseudomonas in JY409, Cronobacter in moderately resistant ZN106, and unclassified Rhizobiaceae and Streptomyces in susceptible ZN6. The predominant root bacterium Massilia accounted for the relative abundance of up to 28.08–61.55%, but dramatically declined to 9.36% in Foc-inoculated susceptible ZN6. Pseudomonas ASV103 and ASV48 of Pseudomonadaceae and Cronobacter ASV162 of Enterobacteriaceae were consistently differential across the cultivars at the phylum, genus, and ASV levels. Using the culture-based method, antagonistic strains of Enterobacteriaceae with a high proportion of 51% were isolated. Furthermore, the bacterial complexes of Pantoea dispersa E318 + Pseudomonas koreensis Ps213 and Cronobacter spp. C1 + C7 reduced the disease index of CFW by 77.2% and 60.0% in the pot experiment, respectively. This study reveals the co-association of specific root bacteria with host plants and reveals insight into the suppressing mechanism of resistant cultivars against CFW disease by regulating the root microbiota. Full article

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2022

Jump to: 2025, 2024, 2023

16 pages, 2302 KiB

Open AccessArticle

New Bacillus subtilis Strains Isolated from Prosopis glandulosa Rhizosphere for Suppressing Fusarium Spp. and Enhancing Growth of Gossypium hirsutum L.

by Ali Abdelmoteleb, Lizbeth Moreno-Ramírez, Benjamín Valdez-Salas, Mahmoud F. Seleiman, Salah El-Hendawy, Khalid J. Aldhuwaib, Majed Alotaibi and Daniel González-Mendoza

Biology 2023, 12(1), 73; https://doi.org/10.3390/biology12010073 - 31 Dec 2022

Cited by 15 | Viewed by 3553

Abstract

Rhizobacteria from desert plants can alleviate biotic stress and suppress plant diseases, and consequently can enhance plant growth. Therefore, the current study was performed to isolate and identify Prosopis glandulosa-associating rhizobacteria based on their antagonistic activity against Fusarium species and plant growth-promoting [...] Read more.

Rhizobacteria from desert plants can alleviate biotic stress and suppress plant diseases, and consequently can enhance plant growth. Therefore, the current study was performed to isolate and identify Prosopis glandulosa-associating rhizobacteria based on their antagonistic activity against Fusarium species and plant growth-promoting properties. Three bacterial isolates were identified as Bacillus subtilis: LDA-1, LDA-2, and LDA-3. The molecular analysis suggests the biosynthesis of the bacteriocins subtilisin and subtilosin, as well as the lipopeptide iturin, by these strains. In addition, the antagonistic study by dual-culture assay showed a high efficacy of all B. subtilis strains against phytopathogenic fungi (Fusarium nygamai, F. equisseti, F. solani, F. solani ICADL1, and F. oxysporum ICADL2) with inhibition percentages ranging from 43.3 to 83.5% in comparison to the control. Moreover, atomic force microscopy (AFM) analysis showed significant differences in the cell wall topography of the F. solani ICADL1 among the treated mycelia and untreated control. As a result, these three B. subtilis strains were used as bioinoculants for cotton seedlings infected by F. solani ICADL1 in pot trials, and the results revealed that the bacterial inoculations as an individual or combined with F. solani ICADL1 significantly improved cotton root and stem length, lateral roots, indole acetic acid (IAA), and gibberellic acid (GA₃) contents, as well as increased antioxidants, flavonoids, and phenols in comparison to those obtained from healthy and infected control plants. In conclusion, the three bacterial strains of B. subtilis (i.e., LDA-1, LDA-2, and LDA-3) are considered promising tools as biocontrol agents for F. solani and cotton growth promoters, and consequently can be used as bio-ertilizer in sustainable agriculture systems. Full article

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21 pages, 2509 KiB

Open AccessReview

Bacillus spp. as Bioagents: Uses and Application for Sustainable Agriculture

by Aimen Razzaq Khan, Adeena Mustafa, Sajjad Hyder, Mohammad Valipour, Zarrin Fatima Rizvi, Amjad Shahzad Gondal, Zubaida Yousuf, Rashid Iqbal and Umar Daraz

Biology 2022, 11(12), 1763; https://doi.org/10.3390/biology11121763 - 5 Dec 2022

Cited by 69 | Viewed by 8194

Abstract

Food security will be a substantial issue in the near future due to the expeditiously growing global population. The current trend in the agriculture industry entails the extravagant use of synthesized pesticides and fertilizers, making sustainability a difficult challenge. Land degradation, lower production, [...] Read more.

Food security will be a substantial issue in the near future due to the expeditiously growing global population. The current trend in the agriculture industry entails the extravagant use of synthesized pesticides and fertilizers, making sustainability a difficult challenge. Land degradation, lower production, and vulnerability to both abiotic and biotic stresses are problems caused by the usage of these pesticides and fertilizers. The major goal of sustainable agriculture is to ameliorate productivity and reduce pests and disease prevalence to such a degree that prevents large-scale damage to crops. Agriculture is a composite interrelation among plants, microbes, and soil. Plant microbes play a major role in growth promotion and improve soil fertility as well. Bacillus spp. produces an extensive range of bio-chemicals that assist in plant disease control, promote plant development, and make them suitable for agricultural uses. Bacillus spp. support plant growth by N fixation, P and K solubilization, and phytohormone synthesis, in addition to being the most propitious biocontrol agent. Moreover, Bacilli excrete extracellular metabolites, including antibiotics, lytic enzymes, and siderophores, and demonstrate antagonistic activity against phytopathogens. Bacillus spp. boosts plant resistance toward pathogens by inducing systemic resistance (ISR). The most effective microbial insecticide against insects and pests in agriculture is Bacillus thuringiensis (Bt). Additionally, the incorporation of toxin genes in genetically modified crops increases resistance to insects and pests. There is a constant increase in the identified Bacillus species as potential biocontrol agents. Moreover, they have been involved in the biosynthesis of metallic nanoparticles. The main objective of this review article is to display the uses and application of Bacillus specie as a promising biopesticide in sustainable agriculture. Bacillus spp. strains that are antagonistic and promote plant yield attributes could be valuable in developing novel formulations to lead the way toward sustainable agriculture. Full article

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11 pages, 992 KiB

Open AccessArticle

Isolation and Characterization of Novel Biological Control Agent Clostridium beijerinckii against Meloidogyne incognita

by Xinglong Lian, Shuang Liu, Lanyuwen Jiang, Xinyu Bai and Yuanyuan Wang

Biology 2022, 11(12), 1724; https://doi.org/10.3390/biology11121724 - 28 Nov 2022

Cited by 4 | Viewed by 2639

Abstract

One of the most severe soil-borne pathogens in the world is the root-knot nematode (Meloidogyne incognita). Biological control is gaining more importance as environmental awareness increases. Thus, keeping this in mind, a total of 712 bacterial strains were isolated from 117 [...] Read more.

One of the most severe soil-borne pathogens in the world is the root-knot nematode (Meloidogyne incognita). Biological control is gaining more importance as environmental awareness increases. Thus, keeping this in mind, a total of 712 bacterial strains were isolated from 117 rhizosphere soil samples and investigated for potential biological control activity against M. incognita. Strain Sneb518 (Clostridium beijerinckii) was identified as having solid biocontrol activity against M. incognita. Sneb518 demonstrated significant inhibition against M. incognita, with J2 mortality reaching 90.73% at 12 h and with eggs hatching at a rate of 6.00% at 24 h, compared to a hatchability level of 29.07% for the control. Additionally, Sneb518 was excellent for enhancing seed germination. The seeds coated with a fermentation broth containing Sneb518 efficiently boosted the germination rate to 88.49%. The effectiveness and stability of C. beijerinckii Sneb518 against M. incognita were then further evaluated in a greenhouse. According to the pot experiment data, Sneb518 considerably (p < 0.05) reduced the number of root galls and egg masses on roots and also significantly (p < 0.05) increased tomato plant growth. C. beijerinckii Sneb518-treated tomato seedlings exhibited 50.26% biocontrol effectiveness compared to the control group. Our results demonstrate that C. beijerinckii Sneb518 can be a potential biological control agent against root-knot nematode disease and a biomass enhancer. This research will give new options for the sustainable control of root-knot nematode disease in tomatoes and other host plants. Full article

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17 pages, 2487 KiB

Open AccessArticle

The Effect of Date Palm Genotypes on Rhizobacterial Community Structures under Saline Environments

by Aya Al-Busaidi, Bernard R. Glick and Mahmoud W. Yaish

Biology 2022, 11(11), 1666; https://doi.org/10.3390/biology11111666 - 15 Nov 2022

Cited by 8 | Viewed by 2415

Abstract

Some genotypes of date palms (Phoenix dactylifera L.) are salt-tolerant; however, salinity significantly affects others. This study aimed to determine the root epiphytic bacterial contributions to the salt tolerance mechanism in the date palm and to verify if the salt-tolerant “Umsila” and [...] Read more.

Some genotypes of date palms (Phoenix dactylifera L.) are salt-tolerant; however, salinity significantly affects others. This study aimed to determine the root epiphytic bacterial contributions to the salt tolerance mechanism in the date palm and to verify if the salt-tolerant “Umsila” and the salt-susceptible “Zabad” cultivars have different bacterial communities. Therefore, the epiphytic bacterial community structures were investigated in both cultivars when grown under control and salinity conditions. The proximal soils of the roots were collected, the DNA was extracted, and a culture-independent approach using Illumina^® MiSeq™ sequence analysis was carried out to identify the changes in the bacterial community structures in the soil samples due to the changes in salinity and the genotypes of the plants based on 16S rRNA gene sequencing. While salt tolerance response differences were evident between the two cultivars, the 16S rRNA gene sequencing results revealed 771 operational taxonomic units (OTUs), including 62 that were differentially accumulated in response to salinity. The ordination analysis showed significant (p = 0.001) changes among the communities in response to salinity in both cultivars. However, the results showed that the two cultivars had distinct bacterial communities when grown under controlled conditions, whereas they had a more similar bacterial community structure when grown under salinity conditions. The plant genotype does not affect the epiphyte bacterial community structure under salinity, probably because salinity affects the plant-microbe interaction similarly in both cultivars. Also, the identified rhizospheric bacteria are not directly associated with the root’s physiological processes in response to salinity. Full article

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19 pages, 8627 KiB

Open AccessArticle

Ameliorating Drought Effects in Wheat Using an Exclusive or Co-Applied Rhizobacteria and ZnO Nanoparticles

by Faqeer Muhammad, Muhammad Aown Sammar Raza, Rashid Iqbal, Faisal Zulfiqar, Muhammad Usman Aslam, Jean Wan Hong Yong, Muhammad Ahsan Altaf, Bilal Zulfiqar, Jawad Amin and Muhammad Arif Ibrahim

Biology 2022, 11(11), 1564; https://doi.org/10.3390/biology11111564 - 25 Oct 2022

Cited by 32 | Viewed by 3442

Abstract

Drought is a major abiotic factor and affects cereal-based staple food production and reliability in developing countries such as Pakistan. To ensure a sustainable and consistent food supply, holistic production plans involving the integration of several drought mitigation approaches are required. Using a [...] Read more.

Drought is a major abiotic factor and affects cereal-based staple food production and reliability in developing countries such as Pakistan. To ensure a sustainable and consistent food supply, holistic production plans involving the integration of several drought mitigation approaches are required. Using a randomized complete block design strategy, we examined the drought-ameliorating characteristics of plant growth-promoting rhizobacteria (PGPR) and nanoparticles (NPs) exclusively or as a combined application (T₄) through three stages (D₁, D₂, and D₃) of wheat growth (T₁, control). Our field research revealed that Azospirillum brasilense alone (T₂) and zinc oxide NPs (T₃) improved wheat plant water relations, chlorophyll, proline, phenolics and grain quality, yield, and their allied traits over the stressed treatments. Specifically, the best outcome was observed in the combined treatment of PGPR and ZnO NPs (T₄). Interestingly, the combined treatment delivered effective drought mitigation through enhanced levels of antioxidants (15% APX, 27% POD, 35% CAT, 38% PPO and 44% SOD) over controls at the grain-filling stage (GFS, D₃ × T₁). The 40% improvements were recorded under the combined treatment at GFS over their respective controls. Their combined usage (PGPR and ZnO NPs) was concluded as an effective strategy for building wheat resilience under drought, especially in arid and semi-arid localities. Full article

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21 pages, 3959 KiB

Open AccessArticle

Evaluation of the Antifungal Activity of Bacillus amyloliquefaciens and B. velezensis and Characterization of the Bioactive Secondary Metabolites Produced against Plant Pathogenic Fungi

by Shereen A. Soliman, Mona M. Khaleil and Rabab A. Metwally

Biology 2022, 11(10), 1390; https://doi.org/10.3390/biology11101390 - 23 Sep 2022

Cited by 42 | Viewed by 5587

Abstract

Endophytic bacteria are plant-beneficial bacteria with a broad host range. They provide numerous benefits to their hosts, helping them tolerate several biotic and abiotic stresses. An interest has recently been developed in endophytic bacteria which are producing bioactive compounds that contribute to the [...] Read more.

Endophytic bacteria are plant-beneficial bacteria with a broad host range. They provide numerous benefits to their hosts, helping them tolerate several biotic and abiotic stresses. An interest has recently been developed in endophytic bacteria which are producing bioactive compounds that contribute to the biological control of various phytopathogens. This research paper aimed to investigate the potentiality of new local strains of endophytic bacteria such as Bacillus amyloliquefaciens and B. velezensis and the production of several antimicrobial metabolites associated with the biocontrol of Alternaria sp., which cause serious diseases and affect important vegetable crops in Egypt. Twenty-five endophytic bacteria isolates were obtained from different plants cultivated in El-Sharkia Governorate, Egypt. Dual culture technique was used to evaluate the bacterial isolates’ antagonistic potentiality against Alternaria sp. and Helminthosporium sp. The most active bacterial isolates obtained were selected for further screening. The antifungal activity of the most active endophytic bacterial isolate was assessed in vivo on pepper seedlings as a biocontrol agent against Alternaria sp. A significant antifungal activity was recorded with isolates C₁ and T₅ against Alternaria sp. and Helminthosporium sp. The bacterial endophyte discs of C₁ and T₅ showed the highest inhibitory effect against Alternaria sp. at 4.7 and 3.1 cm, respectively, and Helminthosporium sp. at 3.9 and 4.0 cm, respectively. The most active endophytic isolates C₁ and T₅ were identified and the 16S rRNA sequence was submitted to the NCBI GenBank database with accession numbers: MZ945930 and MZ945929 for Bacillus amyloliquefaciens and Bacillus velezensis, respectively. The deformity of pathogenic fungal mycelia of Alternaria sp. and Helminthosporium sp. was studied under the biotic stress of bacteria. The culture filtrates of B. amyloliquefaciens and B. velezensis were extracted with different solvents, and the results indicated that hexane was the most efficient. Gas Chromatography-Mass Spectrometry revealed that Bis (2-ethylhexyl) phthalate, Bis (2-ethylhexyl) ester, and N,N-Dimethyldodecylamine were major constituents of the endophytic crude extracts obtained from B. amyloliquefaciens and B. velezensis. The in vivo results showed that Alternaria sp. infection caused the highest disease incidence, leading to a high reduction in plant height and in the fresh and dry weights of pepper plants. With B. amyloliquefaciens application, DI significantly diminished compared to Alternaria sp. infected pepper plants, resulting in an increase in their morphological parameters. Our findings allow for a reduction of chemical pesticide use and the control of some important plant diseases. Full article

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21 pages, 4751 KiB

Open AccessArticle

Comparative Genomics Insights into a Novel Biocontrol Agent Paenibacillus peoriae Strain ZF390 against Bacterial Soft Rot

by Yurong Zhao, Xuewen Xie, Junhui Li, Yanxia Shi, Ali Chai, Tengfei Fan, Baoju Li and Lei Li

Biology 2022, 11(8), 1172; https://doi.org/10.3390/biology11081172 - 4 Aug 2022

Cited by 5 | Viewed by 3327

Abstract

Bacterial soft rot, caused by Pectobacterium brasiliense, can infect several economically important horticultural crops. However, the management strategies available to control this disease are limited. Plant-growth-promoting rhizobacteria (PGPR) have been considered to be promising biocontrol agents. With the aim of obtaining a [...] Read more.

Bacterial soft rot, caused by Pectobacterium brasiliense, can infect several economically important horticultural crops. However, the management strategies available to control this disease are limited. Plant-growth-promoting rhizobacteria (PGPR) have been considered to be promising biocontrol agents. With the aim of obtaining a strain suitable for agricultural applications, 161 strains were isolated from the rhizosphere soil of healthy cucumber plants and screened through plate bioassays and greenhouse tests. Paenibacillus peoriae ZF390 exhibited an eminent control effect against soft rot disease and a broad antagonistic activity spectrum in vitro. Moreover, ZF390 showed good activities of cellulase, protease, and phosphatase and a tolerance of heavy metal. Whole-genome sequencing was performed and annotated to explore the underlying biocontrol mechanisms. Strain ZF390 consists of one 6,193,667 bp circular chromosome and three plasmids. Comparative genome analysis revealed that ZF390 involves ten gene clusters responsible for secondary metabolite antibiotic synthesis, matching its excellent biocontrol activity. Plenty of genes related to plant growth promotion, biofilm formation, and induced systemic resistance were mined to reveal the biocontrol mechanisms that might consist in strain ZF390. Overall, these findings suggest that strain ZF390 could be a potential biocontrol agent in bacterial-soft-rot management, as well as a source of antimicrobial mechanisms for further exploitation. Full article

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13 pages, 845 KiB

Open AccessReview

Salicylic Acid in Plant Symbioses: Beyond Plant Pathogen Interactions

by Goodluck Benjamin, Gaurav Pandharikar and Pierre Frendo

Biology 2022, 11(6), 861; https://doi.org/10.3390/biology11060861 - 3 Jun 2022

Cited by 37 | Viewed by 6662

Abstract

Plants form beneficial symbioses with a wide variety of microorganisms. Among these, endophytes, arbuscular mycorrhizal fungi (AMF), and nitrogen-fixing rhizobia are some of the most studied and well understood symbiotic interactions. These symbiotic microorganisms promote plant nutrition and growth. In exchange, they receive [...] Read more.

Plants form beneficial symbioses with a wide variety of microorganisms. Among these, endophytes, arbuscular mycorrhizal fungi (AMF), and nitrogen-fixing rhizobia are some of the most studied and well understood symbiotic interactions. These symbiotic microorganisms promote plant nutrition and growth. In exchange, they receive the carbon and metabolites necessary for their development and multiplication. In addition to their role in plant growth and development, these microorganisms enhance host plant tolerance to a wide range of environmental stress. Multiple studies have shown that these microorganisms modulate the phytohormone metabolism in the host plant. Among the phytohormones involved in the plant defense response against biotic environment, salicylic acid (SA) plays an important role in activating plant defense. However, in addition to being a major actor in plant defense signaling against pathogens, SA has also been shown to be involved in plant–microbe symbiotic interactions. In this review, we summarize the impact of SA on the symbiotic interactions. In addition, we give an overview of the impact of the endophytes, AMF, and rhizobacteria on SA-mediated defense response against pathogens. Full article

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14 pages, 2376 KiB

Open AccessArticle

Effects of Bacillus subtilis T6-1 on the Rhizosphere Microbial Community Structure of Continuous Cropping Poplar

by Junkang Sui, Qianqian Yu, Kai Yang, Jiayi Yang, Chenyu Li and Xunli Liu

Biology 2022, 11(5), 791; https://doi.org/10.3390/biology11050791 - 23 May 2022

Cited by 7 | Viewed by 2603

Abstract

The continuous cropping obstacles in poplar cultivation cause declines in wood yield and serious soil-borne diseases, mainly because of structural alterations in the microbial community and the aggregation of pathogenic fungi. Bacillus subtilis T6-1, isolated from poplar rhizospheric soil, has strong antagonistic effects [...] Read more.

The continuous cropping obstacles in poplar cultivation cause declines in wood yield and serious soil-borne diseases, mainly because of structural alterations in the microbial community and the aggregation of pathogenic fungi. Bacillus subtilis T6-1, isolated from poplar rhizospheric soil, has strong antagonistic effects on poplar pathogens. We aimed to investigate the effects of B. subtilis T6-1 on the structure of the microbial community in the poplar rhizosphere. Poplar seedlings were replanted in three successive generations of soil. The diameter at breast height, plant height, and the number of culturable bacteria of the poplars inoculated with T6-1 exceeded those in the non-inoculated control group. qPCR analysis revealed that the total abundance of T6-1 bacteria in the treated poplars was remarkably higher in contrast to that in the control group. Illumina MiSeq sequencing was employed to track the alterations in diversity and structure of the total microbial community in the poplar rhizosphere inoculated with B. subtilis T6-1. Fungal diversity and abundance in the T6-1 rhizosphere were remarkably lower in contrast with those in the control rhizosphere. The proportion of Bacillus sp. in the total bacterial community in the T6-1 and control groups was 3.04% and 2.38%, respectively, while those of the Rhizoctonia sp. was 2.02% and 5.82%, respectively. In conclusion, B. subtilis T6-1 has the potential to serve as a microbial agent, enhancing the structure of the rhizosphere microbial community as well as promoting tree growth in poplar cultivation. Full article

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34 pages, 1210 KiB

Open AccessReview

Utilization of Legume-Nodule Bacterial Symbiosis in Phytoremediation of Heavy Metal-Contaminated Soils

by Monika Elżbieta Jach, Ewa Sajnaga and Maria Ziaja

Biology 2022, 11(5), 676; https://doi.org/10.3390/biology11050676 - 27 Apr 2022

Cited by 53 | Viewed by 6533

Abstract

With the increasing industrial activity of the growing human population, the accumulation of various contaminants in soil, including heavy metals, has increased rapidly. Heavy metals as non-biodegradable elements persist in the soil environment and may pollute crop plants, further accumulating in the human [...] Read more.

With the increasing industrial activity of the growing human population, the accumulation of various contaminants in soil, including heavy metals, has increased rapidly. Heavy metals as non-biodegradable elements persist in the soil environment and may pollute crop plants, further accumulating in the human body causing serious conditions. Hence, phytoremediation of land contamination as an environmental restoration technology is desirable for both human health and broad-sense ecology. Legumes (Fabaceae), which play a special role in nitrogen cycling, are dominant plants in contaminated areas. Therefore, the use of legumes and associated nitrogen-fixing rhizobia to reduce the concentrations or toxic effects of contaminants in the soil is environmentally friendly and becomes a promising strategy for phytoremediation and phytostabilization. Rhizobia, which have such plant growth-promoting (PGP) features as phosphorus solubilization, phytohormone synthesis, siderophore release, production of beneficial compounds for plants, and most of all nitrogen fixation, may promote legume growth while diminishing metal toxicity. The aim of the present review is to provide a comprehensive description of the main effects of metal contaminants in nitrogen-fixing leguminous plants and the benefits of using the legume–rhizobium symbiosis with both wild-type and genetically modified plants and bacteria to enhance an efficient recovery of contaminated lands. Full article

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26 pages, 754 KiB

Open AccessReview

Recent Advances in Bacterial Amelioration of Plant Drought and Salt Stress

by Elisa Gamalero and Bernard R. Glick

Biology 2022, 11(3), 437; https://doi.org/10.3390/biology11030437 - 12 Mar 2022

Cited by 113 | Viewed by 8932

Abstract

The recent literature indicates that plant growth-promoting bacteria (PGPB) employ a range of mechanisms to augment a plant’s ability to ameliorate salt and drought stress. These mechanisms include synthesis of auxins, especially indoleacetic acid, which directly promotes plant growth; synthesis of antioxidant enzymes [...] Read more.

The recent literature indicates that plant growth-promoting bacteria (PGPB) employ a range of mechanisms to augment a plant’s ability to ameliorate salt and drought stress. These mechanisms include synthesis of auxins, especially indoleacetic acid, which directly promotes plant growth; synthesis of antioxidant enzymes such as catalase, superoxide dismutase and peroxidase, which prevents the deleterious effects of reactive oxygen species; synthesis of small molecule osmolytes, e.g., trehalose and proline, which structures the water content within plant and bacterial cells and reduces plant turgor pressure; nitrogen fixation, which directly improves plant growth; synthesis of exopolysaccharides, which protects plant cells from water loss and stabilizes soil aggregates; synthesis of antibiotics, which protects stress-debilitated plants from soil pathogens; and synthesis of the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, which lowers the level of ACC and ethylene in plants, thereby decreasing stress-induced plant senescence. Many of the reports of overcoming these plant stresses indicate that the most successful PGPB possess several of these mechanisms; however, the involvement of any particular mechanism in plant protection is nearly always inferred and not proven. Full article

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27 pages, 3283 KiB

Open AccessReview

Rhizosphere Tripartite Interactions and PGPR-Mediated Metabolic Reprogramming towards ISR and Plant Priming: A Metabolomics Review

by Manamele D. Mashabela, Lizelle A. Piater, Ian A. Dubery, Fidele Tugizimana and Msizi I. Mhlongo

Biology 2022, 11(3), 346; https://doi.org/10.3390/biology11030346 - 22 Feb 2022

Cited by 52 | Viewed by 7464

Abstract

Plant growth-promoting rhizobacteria (PGPR) are beneficial microorganisms colonising the rhizosphere. PGPR are involved in plant growth promotion and plant priming against biotic and abiotic stresses. Plant–microbe interactions occur through chemical communications in the rhizosphere and a tripartite interaction mechanism between plants, pathogenic microbes [...] Read more.

Plant growth-promoting rhizobacteria (PGPR) are beneficial microorganisms colonising the rhizosphere. PGPR are involved in plant growth promotion and plant priming against biotic and abiotic stresses. Plant–microbe interactions occur through chemical communications in the rhizosphere and a tripartite interaction mechanism between plants, pathogenic microbes and plant-beneficial microbes has been defined. However, comprehensive information on the rhizosphere communications between plants and microbes, the tripartite interactions and the biochemical implications of these interactions on the plant metabolome is minimal and not yet widely available nor well understood. Furthermore, the mechanistic nature of PGPR effects on induced systemic resistance (ISR) and priming in plants at the molecular and metabolic levels is yet to be fully elucidated. As such, research investigating chemical communication in the rhizosphere is currently underway. Over the past decades, metabolomics approaches have been extensively used in describing the detailed metabolome of organisms and have allowed the understanding of metabolic reprogramming in plants due to tripartite interactions. Here, we review communication systems between plants and microorganisms in the rhizosphere that lead to plant growth stimulation and priming/induced resistance and the applications of metabolomics in understanding these complex tripartite interactions. Full article

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24 pages, 1883 KiB

Open AccessArticle

Plant Beneficial Deep-Sea Actinobacterium, Dermacoccus abyssi MT1.1^T Promote Growth of Tomato (Solanum lycopersicum) under Salinity Stress

by Pharada Rangseekaew, Adoración Barros-Rodríguez, Wasu Pathom-aree and Maximino Manzanera

Biology 2022, 11(2), 191; https://doi.org/10.3390/biology11020191 - 26 Jan 2022

Cited by 25 | Viewed by 5267

Abstract

Salt stress is a serious agricultural problem threatens plant growth and development resulted in productivity loss and global food security concerns. Salt tolerant plant growth promoting actinobacteria, especially deep-sea actinobacteria are an alternative strategy to mitigate deleterious effects of salt stress. In this [...] Read more.

Salt stress is a serious agricultural problem threatens plant growth and development resulted in productivity loss and global food security concerns. Salt tolerant plant growth promoting actinobacteria, especially deep-sea actinobacteria are an alternative strategy to mitigate deleterious effects of salt stress. In this study, we aimed to investigate the potential of deep-sea Dermacoccus abyssi MT1.1^T to mitigate salt stress in tomato seedlings and identified genes related to plant growth promotion and salt stress mitigation. D. abyssi MT1.1^T exhibited plant growth promoting traits namely indole-3-acetic acid (IAA) and siderophore production and phosphate solubilization under 0, 150, 300, and 450 mM NaCl in vitro. Inoculation of D. abyssi MT1.1^T improved tomato seedlings growth in terms of shoot length and dry weight compared with non-inoculated seedlings under 150 mM NaCl. In addition, increased total soluble sugar and total chlorophyll content and decreased hydrogen peroxide content were observed in tomato inoculated with D. abyssi MT1.1^T. These results suggested that this strain mitigated salt stress in tomatoes via osmoregulation by accumulation of soluble sugars and H₂O₂ scavenging activity. Genome analysis data supported plant growth promoting and salt stress mitigation potential of D. abyssi MT1.1^T. Survival and colonization of D. abyssi MT1.1^T were observed in roots of inoculated tomato seedlings. Biosafety testing on D. abyssi MT1.1^T and in silico analysis of its whole genome sequence revealed no evidence of its pathogenicity. Our results demonstrate the potential of deep-sea D. abyssi MT1.1^T to mitigate salt stress in tomato seedlings and as a candidate of eco-friendly bio-inoculants for sustainable agriculture. Full article

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26 pages, 3144 KiB

Open AccessArticle

Perception of Biocontrol Potential of Bacillus inaquosorum KR2-7 against Tomato Fusarium Wilt through Merging Genome Mining with Chemical Analysis

by Maedeh Kamali, Dianjing Guo, Shahram Naeimi and Jafar Ahmadi

Biology 2022, 11(1), 137; https://doi.org/10.3390/biology11010137 - 14 Jan 2022

Cited by 23 | Viewed by 4520

Abstract

Tomato Fusarium wilt, caused by Fusarium oxysporum f. sp. lycopersici (Fol), is a destructive disease that threatens the agricultural production of tomatoes. In the present study, the biocontrol potential of strain KR2-7 against Fol was investigated through integrated genome mining and [...] Read more.

Tomato Fusarium wilt, caused by Fusarium oxysporum f. sp. lycopersici (Fol), is a destructive disease that threatens the agricultural production of tomatoes. In the present study, the biocontrol potential of strain KR2-7 against Fol was investigated through integrated genome mining and chemical analysis. Strain KR2-7 was identified as B. inaquosorum based on phylogenetic analysis. Through the genome mining of strain KR2-7, we identified nine antifungal and antibacterial compound biosynthetic gene clusters (BGCs) including fengycin, surfactin and Bacillomycin F, bacillaene, macrolactin, sporulation killing factor (skf), subtilosin A, bacilysin, and bacillibactin. The corresponding compounds were confirmed through MALDI-TOF-MS chemical analysis. The gene/gene clusters involved in plant colonization, plant growth promotion, and induced systemic resistance were also identified in the KR2-7 genome, and their related secondary metabolites were detected. In light of these results, the biocontrol potential of strain KR2-7 against tomato Fusarium wilt was identified. This study highlights the potential to use strain KR2-7 as a plant-growth promotion agent. Full article

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