Search Results (290)

Carbon quantum dots (CQD) are an emergent nanomaterial with unique optical and biological properties. However, the purification of CQD is one of the bottlenecks that makes it difficult to scale for application in different areas. In this work, we explore for the first time the potential of centrifugal partition chromatography (CPC) as an alternative preparative technology to achieve the purification of CQD at the gram scale. The hydrothermal method was used to synthesize CQD from avocado peels. After 6 h at 250 °C, a complex mix of strong blue-fluorescent CQDs were obtained and submitted to CPC fractionation without pretreatment. The best results were obtained with the solvent system n-hexane–ethyl acetate–methanol–water (1:2:1:2, v/v/v/v), in an elution-extrusion protocol. Nine fractions were obtained and were characterized by UV-VIS spectrophotometry, Fourier transform infrared (F-TIR), and field emission scanning electron microscopy (FESEM), confirming the presence of CQD of different sizes. CPC fractionations indicate that a polarity-based separation mechanism can be used to purify CQD. Interestingly, four fractions showed antibacterial and anti-biofilm effects on Pseudomonas putida and Listeria monocytogenes. Therefore, CPC allows for better refining of this type of nanomaterial, and in combination with other techniques, it would serve to obtain CQD of higher purity, facilitating the physicochemical and bioactivity characterization of these particles. CPC would also allow the use of waste, such as avocado peels, to obtain new materials. Full article

Bivalve mollusks face a crisis due to infectious diseases, resulting in high mortality and economic losses. The need for continuous monitoring to prevent contamination from sewage and rainwater in aquaculture is evident. The recent mass mortality of scallops in Ilha Grande Bay (IGB), Rio de Janeiro’s largest scallop producer, due to environmental contaminants underscores the need for further research. This study aims to investigate the recent collapse of the scallop population and assess the human impact by analyzing the circulation of pathogens. Materials and Methods: Mollusks were collected from three sites in Ilha Grande Bay (IGB), a region known for its significant scallop production, and from scallop farms in Angra dos Reis, RJ. A total of 216 gill and adductor tissue samples from lion’s foot scallops were analyzed. Bacterial contamination was identified using MALDI-TOF, while antimicrobial susceptibility and carbapenem production were assessed via disk diffusion tests. Results: Mollusks were contaminated with V. alginolyticus, V. fluvialis, V. harveyi, Pseudomonas putida, and Pseudomonas monteilii. All isolates were sensitive to meropenem, but P. putida showed higher resistance to ciprofloxacin. Conclusions: The presence of these pathogenic and resistant bacteria in scallop adductor tissues is a concern for the aquaculture industry and a significant public health risk. The potential for these bacteria to enter the human food chain through consuming contaminated seafood or recreational activities such as bathing is a serious issue that needs to be addressed. Full article

Dairy-borne Pseudomonas spp., known for causing spoilage, may also exhibit antibiotic resistance and form biofilms, enhancing their persistence in dairy environments and contaminating final products. This study examined biofilm formation and antibiotic resistance in 106 Pseudomonas spp. strains isolated from milk, whey, and spoiled dairy products. Phylogenetic analysis (based on partial ileS sequences) grouped most strains within the P. fluorescens group, clustering into the P. fluorescens, P. gessardii, P. koorensis, and P. fragi subgroups. Biofilm formation in polystyrene microplates was assessed at 6 °C and 25 °C by crystal violet staining. After 48 h, 72% and 65% of Pseudomonas strains formed biofilms at 6 °C and 25 °C, respectively, with higher biomass production at 6 °C. High biofilm producers included most P. fluorescens, P. shahriarae, P. salmasensis, P. atacamensis, P. gessardii, P. koreensis, and P. lundensis strains. The adnA gene, associated with biofilm formation, was detected in 60% of the biofilm producers, but was absent in P. fragi, P. lundensis, P. weihenstephanensis, and P. putida. Antibiotic susceptibility was tested using the disk diffusion method. All strains were susceptible to amikacin and tobramycin; however, 73% of the strains were resistant to aztreonam, 28% to imipenem and doripenem, 19% to ceftazidime, 13% to meropenem, and 7% to cefepime. A multiple antibiotic resistance index (MARI) > 0.2 was found in 30% of the strains, including multidrug-resistant (n = 15) and extensively drug-resistant (n = 3) strains. These findings highlight Pseudomonas spp. as persistent contaminants and antibiotic resistance reservoirs in dairy environments and products, posing public health risks and economic implications for the dairy industry. Full article

With the development of the aquatic products processing industry, 6–8 million tons of shrimp and crab shell waste are produced globally annually, but, due to the lack of high-value conversion technology, crab shells are often discarded in large quantities as a by-product of processing. Pseudomonas-based microbial cell factories are capable of biosynthesis of high-value products using a wide range of substrates; however, there is currently no reliable fermentation model for producing high-value chemicals using crab shell waste by Pseudomonas strains. In this study, we first explored the culture conditions of shell fermentation using KT2440 through single-factor and orthogonal experiments, and the optimized fermentation parameters obtained are given as follows: a temperature of 30 °C, fermentation time of 42 h, substrate solid–liquid ratio of 7%, and rotational speed of 200 rpm. After optimization, the maximum cell growth was increased by 64.39% from 350.67 × 10⁸ CFU/mL to 576.44 × 10⁸ CFU/mL. Combined with engineering modification, two engineered strains, KT_+IV and KT_+lasBT, expressing exogenous proteases, were obtained, and the maximum growth was increased from 316.44 × 10⁸ CFU/mL to 1268.44 × 10⁸ CFU/mL and 616.89 × 10⁸ CFU/mL, which were 300.84% and 94.94% higher, respectively. In addition, the engineered strain KT_+NtrcT-D55E, which regulates nitrogen metabolism, was obtained, and the accumulation of intracellular polyhydroxy fatty acid esters (PHA) was increased from 20.00 mg/L to 78.58 mg/L, which was a significant increase of 292.93% relative to the control group. This study provides a theoretical basis and technical support for the high-value utilization of shrimp and crab shell resources and the development of environmentally friendly bioproducts. Full article

Metabolic engineering of the shikimate pathway offers a promising strategy for enhancing the production of aromatic compounds in microbial hosts. However, feedback inhibition of key enzymes, such as the 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase (DAHP synthase), often limits the yield of target products. In this study, we focused on the DAHP synthase (AroF-I) from Pseudomonas putida. Through computational modeling and experimental validation, we identified specific amino-acid residues responsible for tyrosine-mediated feedback inhibition. By targeted mutagenesis, we engineered DAHP synthase variants that exhibit reduced sensitivity to feedback inhibition. The introduction of these engineered enzymes into a metabolically engineered Pseudomonas putida strain resulted in significantly increased production of p-coumaric acid. Our findings provide valuable insights into the regulation of the shikimate pathway and demonstrate the potential of protein engineering to improve microbial production of aromatic compounds. Full article

Long non-coding RNAs (lncRNAs) represent a class of non-coding RNAs. In the study of Pseudomonas putida Sneb821-induced tomato resistance to Meloidogyne incognita, reverse transcription polymerase chain reaction (RT-PCR) was employed to validate 12 lncRNAs in tomato. Among them, the lncRNA47258/miR319b/TCP molecular regulatory module was likely implicated in the process of Sneb821-induced tomato resistance against M. incognita. Through the application of tomato hairy root and virus-induced gene silencing (VIGS) technologies for the investigation of lncRNA47258, it was determined that lncRNA47258 could target the TCP (Solyc07g062681.1) gene and modulate the metabolic pathway of tomato jasmonic acid-related indices, thereby impeding the infection of M. incognita. Moreover, the overexpression of the target gene TCP (Solyc07g062681.1) using tomato hairy root technology demonstrated that it could regulate the jasmonic acid synthesis pathway in tomato, consequently obstructing the infection and suppressing the development of M. incognita. Collectively, lncRNA47258/miR319b/TCP (Solyc07g062681.1) was preliminarily verified to be involved in the Sneb821-induced resistance process against M. incognita in tomato. Full article

Microbial inoculation plays a crucial role in shaping plant physiological and biochemical responses, influencing growth, secondary metabolism, and stress-related markers. This study investigates the effects of PAH-degrading microorganisms (Pseudomonas putida, Sphingobium yanoikuyae, and Rhodotorula sphaerocarpa) on the growth, secondary metabolism, photosynthetic pigment, and stress-related biochemical markers of silver birch (Betula pendula Roth) seedlings from two half-sib families grown hydroponically. Results demonstrate family-dependent variations in the response to microbial treatments. In family 73, the growth of both shoots and roots was inhibited by certain microbial treatments, along with a decrease in key biochemical markers such as phenolic content and carotenoids. Conversely, family 86 showed no growth inhibition and exhibited improvements in some biochemical markers, including flavonoids and chlorophyll. Stress indicators, such as malondialdehyde (MDA) and soluble sugars, displayed contrasting patterns between families, with increased MDA observed in family 73 under certain microbial treatments. In contrast, family 86 did not exhibit an increase in MDA, suggesting differences in stress mitigation. Soluble sugars were generally reduced in family 73. Antioxidant enzyme activity further highlighted these family-specific responses, with variations in enzymes like ascorbate peroxidase (APX) and guaiacol peroxidase (POX) across treatments. Notably, significant interactions between family and microbial treatments were observed for several oxidative stress enzymes, underscoring the role of genotype in shaping the response to microbial stress. These findings highlight the genotype-dependent interactions between microbial inoculation and plant secondary metabolism, providing insights into the role of specifically selected microbial inoculation in stress mitigation and growth regulation. Full article

Plastics are indispensable to modern life, but their widespread use has created an environmental crisis due to inefficient waste management. Mixed plastic waste, comprising diverse polymers, presents significant recycling challenges due to the high costs of sorting and processing, leading to ecosystem accumulation and harmful by-product generation. This study addresses this issue by engineering a synthetic bacterial consortium (SBC) designed to degrade mixed plastic monomers. The consortium pairs Escherichia coli Nissle 1917, which uses ethylene glycol (EG), a monomer derived from polyethylene terephthalate (PET), as a carbon source, with Pseudomonas putida KT2440, which metabolizes hexamethylenediamine (HD), a monomer from nylon-6,6, as a nitrogen source. Adaptive evolution of the SBC revealed a novel metabolic interaction where P. putida developed the ability to degrade both EG and HD, while E. coli played a critical role in degrading glycolate, mitigating its by-product toxicity. The evolved cross-feeding pattern enhanced biomass production, metabolic efficiency, and community stability compared to monocultures. The consortium’s performance was validated through flux balance analysis (FBA), high-performance liquid chromatography (HPLC), and growth assays. These findings highlight the potential of cross-feeding SBCs in addressing complex plastic waste, offering a promising avenue for sustainable bioremediation and advancing future polymer degradation strategies. Full article

Bioplastics are emerging as a promising solution to reduce pollution caused by petroleum-based plastics. Among them, polyhydroxyalkanoates (PHAs) stand out as viable biotechnological alternatives, though their commercialization is limited by expensive downstream processes. Traditional PHA extraction methods often involve toxic solvents and high energy consumption, underscoring the need for more sustainable approaches. This study evaluated physical and chemical methods to extract PHAs from Pseudomonas putida U, a bacterium known to produce poly-3-hydroxyoctanoate P(3HO). Lyophilized cells underwent six extraction methods, including the use of the following: boiling, sonication, sodium hypochlorite (NaClO), sodium dodecyl sulfate (SDS), sodium hydroxide (NaOH), and chloroform. Physical methods such as boiling and sonication achieved yields of 70% and 60%, respectively, but P(3HO) recovery remained low (30–40%). NaClO extraction provided higher yields (80%) but resulted in significant impurities (70%). NaOH methods offered moderate yields (50–80%), with P(3HO) purities between 50% and 70%, depending on the conditions. Spectroscopic and analytical techniques (FTIR, TGA, NMR, GPC) identified 0.05 M NaOH at 60 °C as the optimal extraction condition, delivering high P(3HO) purity while minimizing environmental impact. This positions NaOH as a sustainable alternative to traditional halogenated solvents, paving the way for more eco-friendly PHA production processes. Full article

Hard yellow maize is a crucial crop in Peruvian agriculture that plays a significant role in food security and livestock production. However, intensive fertilization practices in agronomic management have negatively impacted soil health. To explore more sustainable agricultural technologies, researchers investigated solutions using microorganisms to enhance plant growth. This study assessed the synergistic effects of microbial inoculants and mineral fertilization on INIA 619 and Dekal B-7088 maize varieties’ yield and nutritional quality. A split-plot design was employed, incorporating four inoculation treatments—no inoculant, Bacillus subtilis, Trichoderma viride, and Pseudomonas putida—combined with fertilization levels of 0%, 50%, 75%, and 100%. The findings revealed that Bacillus subtilis boosted yields by 13.1% in INIA 619 and 55.5% in Dekal B-7088. Additionally, combined with 100% fertilization, microbial inoculation increased protein content by 47% and carbohydrates by 6% in INIA 619 while maintaining nutritional quality with 75% fertilization. Similarly, in Dekal B-7088, inoculation with total fertilization enhanced protein content by 54% and fiber by 27%. These results demonstrated that microbial inoculation could reduce mineral fertilization by up to 25% while sustaining high yields and improving the nutritional quality of maize. Full article

Heavy metal pollution from industrial activities and poor waste disposal poses significant environmental and health threats to humans and animals. This calls for sustainable approaches to the cleanup of heavy metals. This review explores metal tolerance mechanisms of bacteria such as the formation of biofilms, efflux systems, and enzymatic detoxification. These mechanisms allow bacteria communities to adapt and survive in contaminated environments. These adaptations are enhanced by mutations in the bacteria genes and by horizontal gene transfers, enabling bacteria species to survive under environmental stress while simultaneously contributing to nutrient cycling and the decomposition of organic matter. This review further explores the symbiotic interactions between bacteria, plants, and animals. These relationships enhance the metal tolerance ability of the different living organisms involved and are also very important in the bioremediation and phytoremediation of heavy metals. Plant growth-promoting rhizobacteria, Rhizobium, and Bacillus species are very important contributors to phytoremediation; they improve heavy metal uptake, improve the growth of roots, and plants resilience to stress. Moreover, this review highlights the importance of genetically engineered bacteria in closed-loop systems for optimized metal recovery. This offers environmentally friendly and sustainable options to the traditional remediation methods. Engineered Cupriavidus metallidurans CH34 and Pseudomonas putida strain 15420352 overexpressing metallothioneins have shown enhanced metal-binding capabilities, which makes them very effective in the treatment of industrial wastewaters and in biosorption applications. The use of engineered bacteria for the cleanup of heavy metals in closed-loop systems promotes the idea of a circular economy by recycling metals, thus reducing environmental waste. Multidisciplinary research that integrates synthetic biology, microbial ecology, and environmental science is very important for the advancement of metal bioremediation technologies. This review’s analysis on bacterial metal tolerance, symbiosis, and bioengineering strategies offers a pathway to effective bioremediation options, for the reclamation of heavy metal-polluted environments while promoting sustainable environmental practices. Full article

Pseudomonas putida PCL1760 is a well-studied bacterium that can be used for a wide range of biotechnological applications. In our study we investigated the effect of deletion of the genes involved in alginate accumulation (algA), flagellar export (flhA), and pili formation pilQ on the behavior of the strain in bioreactors. We obtained the knockout mutant P. putida LN6160 with the deletion of these genes and showed that the absence of these genes reduces mobility and biofilm formation (40% lower after 72 h) in the mutant. At the same time, we noted the positive effect of these deletions on the growth of the mutant strain on rich medium (1.39 × 10¹⁰ CFU/mL in the mutant and 6.4 × 10⁹ CFU/mL in the wild type) and on mineral medium (6.11 × 10⁹ CFU/mL in the mutant and 1.36 × 10⁹ CFU/mL in the wild type) by growing them in small-volume bioreactors. A significant decrease in the biofilm and the foam formation was also observed for LN6160 in a small-volume bioreactor. Most probably, the rapid growth of the deletion strain occurs due to a decrease in the energy load on the bacterial apparatus. Full article

The development of multidrug resistance by pathogenic bacteria and yeast is a significant medical problem that needs to be addressed. One possible answer could be the combined use of antibiotics and silver nanoparticles, which have different mechanisms of antimicrobial action. In the same way, these nanoparticles can be combined with antifungal agents. Biogenic silver nanoparticles synthesized using environmentally friendly biosynthesis technology using extracts of biologically active plants are an effective nanomaterial that needs to be comprehensively investigated for implementation into medical practice. In this study, the synergistic effects arising from their combined use with antibiotics and fungicides against various bacteria and yeasts were studied. The following methods were used: disco-diffusion analysis and construction of plankton culture growth curves. The synergistic effect of silver nanoparticles and antibiotics (fungicides) has been determined. Effective concentrations of substances were established, recommendations for the studied pathogenic species were presented, and the effect of destruction of the bacterial membrane was illustrated. The most significant synergistic effect was manifested in pathogenic candida and brewer’s yeast. Full article

Background/Objectives: Vitamin B₁₂ is very important for human health, as it is a cofactor for enzymatic activities and plays various roles in human physiology. It is highly valued in the pharmaceutical, food, and additive production industries. Some of the bacteria currently used for the vitamin production are difficult to modify with gene-editing tools and may have slow growth. We propose the use of the bacteria Pseudomonas putida KT2440 for the production of vitamin B₁₂ because it has a robust chassis for genetic modifications. The present wok evaluates P. putida KT2440 as a host for vitamin B₁₂ production and explore potential gene-editing optimization strategies. Methods: We curated and modified a genome-scale metabolic model of Pseudomonas putida KT2440 and evaluated different strategies to optimize vitamin B₁₂ production using the knockin and OptGene algorithms from the COBRA Toolbox. Furthermore, we examined the presence of riboswitches as cis-regulatory elements and calculated theoretical biomass growth yields and vitamin B₁₂ production using a flux balance analysis (FBA). Results: According to the flux balance analysis of P. putida KT2440 under culture conditions, the biomass production values could reach 1.802 gDW⁻¹·h¹·L⁻¹, and vitamin B₁₂ production could reach 0.359 µmol·gDW⁻¹·h⁻¹·L⁻¹. The theoretical vitamin B₁₂ synthesis rate calculated using P. putida KT2040 with two additional reactions was 14 times higher than that calculated using the control, Pseudomonas denitrificans, which has been used for the industrial production of this vitamin. Conclusions: We propose that, with the addition of aminopropanol linker genes and the modification of riboswitches, P. putida KT2440 may become a suitable host for the industrial production of vitamin B₁₂. Full article

Phytophthora capsici is a devastating pathogen in horticultural crops, particularly affecting Capsicum annuum (pepper). The overuse of chemical fungicides has led to resistance development, necessitating alternative strategies. This study investigates the antagonistic effects of four rhizobacterial isolates (Bacillus sp., Pseudomonas putida, Bacillus subtilis, Bacillus amyloliquefaciens) against P. capsici, focusing on the production of volatile organic compounds (VOCs). Using in vitro dual culture assays, we observed a significant inhibition of mycelial growth and sporangia production, especially by B. subtilis and B. amyloliquefaciens. The GC-MS/SPME-HS analysis identified key VOCs responsible for these antagonistic effects. Our findings demonstrate that specific rhizobacteria and their VOCs offer a promising biocontrol strategy, potentially reducing the reliance on chemical fungicides and contributing to sustainable agriculture. Full article