Search Results (212)

Background/Objectives: The presence of multi-drug-resistant (MDR) bacteria in healthy individuals poses a significant public health concern, as these strains may contribute to or even facilitate the dissemination of antibiotic resistance genes (ARGs) and virulence factors. In this study, we investigated the genomic features of antimicrobial-producing Escherichia coli strains from the gut microbiota of healthy individuals in Singapore. Methods: Using a large-scale screening approach, we analyzed 3107 E. coli isolates from 109 fecal samples for inhibitory activity against E. coli DH5α and performed whole-genome sequencing on 37 representative isolates. Results: Our findings reveal genetically diverse strains, with isolates belonging to five phylogroups (A, B1, B2, D, and F) and 23 unique sequence types (STs). Bacteriocin gene clusters were widespread (92% of isolates carried one or more bacteriocin gene clusters), with colicins and microcins dominating the profiles. Notably, we identified an hcp-et3-4 gene cluster encoding an effector linked to a Type VI secretion system. Approximately 40% of the sequenced isolates were MDR, with resistance for up to eight antibiotic classes in one strain (strain D96). Plasmids were the primary vehicles for ARG dissemination, but chromosomal resistance determinants were also detected. Additionally, over 55% of isolates were classified as potential extraintestinal pathogenic E. coli (ExPEC), raising concerns about their potential pathogenicity outside the intestinal tract. Conclusions: Our study highlights the co-occurrence of bacteriocin genes, ARGs, and virulence genes in gut-residing E. coli, underscoring their potential role in shaping microbial dynamics and antibiotic resistance. While bacteriocin-producing strains show potential as probiotic alternatives, careful assessment of their safety and genetic stability is necessary for therapeutic applications. Full article

Bacteriocins are ribosomal synthesized antimicrobial peptides produced by bacteria, but their low yields limit industrial applications as food preservatives. This study aimed to optimize the culture conditions of Pediococcus acidilactici CCFM18 and investigate the biological properties of the bacteriocin. The culture temperature, initial pH, and culture time significantly affected the growth of P. acidilactici CCFM18 and bacteriocin production. The optimal culture conditions determined through response surface methodology (RSM) were a culture temperature of 35 °C, an initial pH of 7.0, and a growth time of 16 h. Under these conditions, bacteriocin production reached 1454.61 AU/mL, representing a 1.8-fold increase compared to pre-optimization levels. Biological characterization revealed that the bacteriocin exhibited strong thermal stability (up to 100 °C for 30 min) and pH stability (pH 2–9), but was sensitive to proteolytic enzymes, including pepsin, trypsin, papain, and protease K. The bacteriocin demonstrated antimicrobial activity against both Gram-positive and Gram-negative bacteria, including Enterococcus faecalis and Escherichia coli. These findings provide a theoretical basis for the industrial production and application of the bacteriocin. Full article

Class IId bacteriocins are linear, unmodified antimicrobial peptides produced by Gram-positive bacteria, and often display potent, narrow-spectrum inhibition spectra. Garvicin Q (GarQ) is a class IId bacteriocin produced by the lactic acid bacterium Lactococcus garvieae. It stands out for its unusual broad-spectrum antimicrobial activity against various bacterial species, including Listeria monocytogenes, Pediococcus pentosaceus, Carnobacterium maltaromaticum, Enterococcus faecalis, and Lactococcus spp. Its protein target is the mannose phosphotransferase system (Man-PTS) of susceptible bacterial strains, though little is known about the precise molecular mechanism behind GarQ’s unusual broad spectrum of activity. In this work, ¹³C- and ¹⁵N-labelled GarQ was recombinantly produced using our previously described “sandwiched” protein expression system in Escherichia coli. We also developed a protocol to purify a uniformly labelled sample of the small ubiquitin-like modifier His₆-SUMO, which is produced as a byproduct of the expression procedure. We demonstrated its use as a “free” protein standard for 3D NMR experiment calibrations. The GarQ solution structure was solved using triple-resonance nuclear magnetic resonance (NMR) spectroscopy and was compared with the structures of other Man-PTS-targeting bacteriocins. GarQ adopts a helix–hinge–helix fold, which is contrary to its structural predictions according to AlphaFold 3. Full article

The production of fermented sausages from poultry meat using traditional technologies and natural maturation conditions is a major challenge. The aim of this study was to identify indigenous microbiota with antilisterial activity from an innovative, additive-free, traditionally fermented chicken sausage. Isolates (n = 88) of lactic acid bacteria (LAB) were collected during maturation and subjected to MALDI-TOF mass spectrometry identification. The capacity to combat Listeria was screened against five strains using the agar well diffusion method in 63 selected LAB isolates. MALDI-TOF mass spectrometry identified four different LAB genera, namely Enterococcus, Lactococcus, Leuconostoc and Lactobacillus, the proportions of which differed significantly during the production phases (p < 0.001). Enterococcus faecalis was the most prevalent LAB species in the initial sausage dough. The presence of lactococci (Lactococcus lactis) and enterococci was detected during the 14- and 30-day ripening period and was gradually displaced by leuconostocs and lactobacilli. Lactobacilli appeared to be abundant during the central and late maturation phases, and consisted of only two species—Latilactobacillus sakei and Latilactobacillus curvatus. In total, 38 LAB isolates (60%) showed antilisterial activity toward at least one Listeria indicator strain. The proportions of antilisterial LAB differed significantly during sausage maturation. Inhibitory activity against all indicator Listeria was detected in the neutralized cell-free supernatants of five strains of Enterococcus faecalis, two L. sakei strains and one Leuconostoc mesenteroides strain. The antilisterial activity observed in the indigenous LAB revealed the possible role of L. sakei as a bioprotective culture, as well as the role of Ln. mesenteroides and E. faecalis as bacteriocin producers, for practical applications. Full article

Antibiotic-resistant bacteria are major contributors to food spoilage, animal diseases, and the emergence of multidrug-resistant (MDR) bacteria in healthcare, highlighting the urgent need for effective treatments. Bacteriocins produced by lactic acid bacteria (LAB) have gained attention for their non-toxic nature and strong antimicrobial properties. LAB-derived bacteriocins have been successfully applied in food preservation and are classified by the U.S. Food and Drug Administration (FDA) as ‘food-grade’ or ‘generally recognized as safe’ (GRAS). This review summarizes recent progress in the production, purification, and emerging applications of LAB bacteriocins. It emphasizes their versatility in food preservation, agriculture, and medicine, providing insights into their role in antimicrobial development and functional food innovation. Full article

Lactic acid bacteria (LAB) play a crucial role in probiotics, functional foods, and sustainable biotechnologies due to their ability to produce bioactive metabolites such as short-chain fatty acids, bacteriocins, vitamins, and exopolysaccharides. These metabolites aid in gut health, pathogen inhibition, and enhanced productivity in the food, pharmaceutical, and aquaculture industries. However, the high production cost remains a major challenge, necessitating cost-effective media formulations and bioprocess optimization. This review explores strategies for maximizing LAB yields and functionality through the precision control of key cultivation parameters, including temperature, pH, and agitation speed, ensuring probiotic viability in compliance with regulatory standards (≥10⁶ CFU/g or mL). Furthermore, advances in metabolic engineering, synthetic biology, and the utilization of agro-industrial by-products are driving cost-efficient and eco-friendly LAB production. By integrating scalable fermentation technologies with sustainable resource management, LAB have the potential to bridge the gap between food security, environmental sustainability, and biotechnological innovation. This review provides a comprehensive overview of recent advances in LAB cultivation and bioprocess optimization, ensuring high-quality probiotic production for diverse industrial applications. Full article

Background/Objectives: The deterioration of food quality and safety is often linked to the presence of pathogenic and spoilage microorganisms. Postbiotics, including organic acids, enzymes, and bacteriocins produced by lactic acid bacteria (LAB), have emerged as promising next-generation food preservatives. This study investigates the biological and physicochemical properties of several postbiotic-based extracts (PBEs) comprising cell-free supernatant (CFS) and exopolysaccharide (EPS) fractions derived from three native probiotic strains: Lactiplantibacillus plantarum UTNGt2, Lactococcus lactis UTNGt28, and Weissella cibaria UTNGt21O. Methods: The antibacterial activity of these PBEs was assessed against multidrug-resistant Escherichia coli L1PEag1. Moreover, the antioxidant capacity and cytotoxicity along with the characterization of these formulations was assessed. Results: FU6 (CFS UTNGt28: EPS UTNGt2) and FU13 (CFS UTNGt21O) were found as the most potent formulations. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) confirmed dose- and time-dependent damage to the bacterial membrane and cell wall. FU6 exhibited superior antioxidant activity and lacked hemolytic effects, whereas both FU6 and FU13 induced cell-specific responses in HEK293 (human kidney) and HT-29 (intestinal mucus-producing) cell lines. Furthermore, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy identified characteristic absorption bands corresponding to proteins, lipids, carbohydrates, and nucleic acids, while proton nuclear magnetic resonance (¹H-NMR) spectroscopy revealed key monosaccharides, amino acids, and metabolites such as lactate and acetate within the extracts. Conclusions: FU6 and FU13 demonstrate potential as safe and effective postbiotic formulations at non-concentrated doses. However, further research is required to elucidate their molecular composition comprehensively and evaluate their applicability for broader and long-term use in food preservation and pharmaceutical development. Full article

Bacteriocins, ribosomally synthesized by bacteria, have long been recognized for their role in ensuring food safety and security due to their antibacterial effects against foodborne pathogens and spoilage bacteria. However, recent advancements have unveiled their expanding potential beyond food applications, with increasing evidence of their efficacy against clinically significant pathogenic bacteria, biofilm formation, viral infections, and even cancer. These emerging discoveries have continuously added new layers to the application of bacteriocins, extending their relevance from food preservation to broader human health interventions. To further harness this expanding potential, various innovative strategies have been developed to overcome traditional limitations associated with bacteriocin use. Instead of directly employing bacteriocins or bacteriocin-producing bacterial cultures, novel approaches, such as incorporating them into films and packaging materials or coupling them with nanoparticles, have demonstrated enhanced effectiveness. In this review, we examine the evolving landscape of bacteriocin applications and shed light on the expanding functional spectrum of bacteriocins for both food safety and human health, although some important challenges and limitations remain. By analyzing the recent literature and innovative technological advancements, we highlight how bacteriocins are continuously evolving, opening new frontiers for their use and reinforcing their significance beyond their conventional roles. Full article

Raw milk and traditional fermented foods such as artisanal cheese represent a natural source of lactic acid bacteria (LAB). They can produce antimicrobial compounds, such as bacteriocins and lactic acid, which may be exploited in dairy biopreservation. This study aimed to conduct a systematic review and meta-analysis to synthesize the inhibition diameter (ID) of LAB against L. monocytogenes, S. aureus, and Salmonella spp. Literature electronic searches were performed on PubMed, Scopus, and Web of Science, to identify articles that reported data on in-vitro antimicrobial activity by LAB isolated from dairy foods. A total of 1665 papers were retrieved, and 20 primary studies were selected according to the selection criteria, of which 397 observations were extracted. Random-effects meta-regression models were employed to describe the effects of LAB genus, pathogen concentration, susceptibility method, incubation time, inoculation volume, agar type and pH on the IDs for L. monocytogens, S. aureus, and Salmonella spp. L. monocytogens was the most susceptible pathogen (p < 0.05) to the LAB effects, followed by S. aureus and Salmonella spp. As a whole, LAB from the Lacticaseibacillus genus were the most effective (p < 0.05) in inhibiting L. monocytogens (21.49 ± 2.654 mm), followed by S. aureus (21.06 ± 2.056 mm). Salmonella spp. presented higher (p < 0.05) susceptibility to Lactobacillus genus (19.93 ± 2.456 mm). From the results, a general trend could be observed for the well-diffusion method to produce higher (p < 0.05) ID estimates than the spot and disk methods (30.73 ± 2.530 mm vs. 21.98 ± 1.309 mm vs. 13.39 ± 1.403 mm for L. monocytogenes; 22.37 ± 1.073 mm vs. 14.91 ± 2.312 mm vs. 20.30 ± 2.319 mm for Salmonella spp.), respectively. Among the tested moderators, the pathogen’s inoculum concentration, the in vitro susceptibility assay itself, incubation time and inoculation volume on agar are determinant parameters to be looked at when designing a robust and reproducible experimental plan. The in vitro results reinforced that LAB can be useful in controlling the development of pathogenic bacteria frequently found in the dairy industry. Full article

The demand for healthier, more natural, and sustainable foods has increased, which drives the development of clean label food products. The clean label trend is associated with developing food products with as few ingredients as possible, free of synthetic additives, and with ingredients that customers understand and consider healthy. Yogurt is a fermented food with numerous health benefits, and is an excellent source of proteins, vitamins, and minerals. However, yogurt may contain chemical additives (including preservatives) that concern consumers as they are associated with potential health risks. Lactic acid bacteria (LAB) are Gram-positive, non-spore-forming, catalase-negative, and non-motile, with antimicrobial activity due to metabolites produced during fermentation. These metabolites include bacteriocins, organic acids, and exopolysaccharides, among others. Thus, in addition to its use in several technological and industrial processes in the food field, LAB present good potential for application as a clean label component for preserving foods, including yogurts. This review article provides an overview of the potential use of LAB and its compounds obtained from fermentation to act as a clean label ingredient in the preservation of yogurts. Full article

Proteus mirabilis has been identified as the third most frequent reason for catheter-associated urinary tract infections. The production of urease significantly enhances the force of catheter blockage caused by biofilm formation. Because biofilms are important virulence factors that make antibiotics less potent, it is becoming increasingly important to develop novel alternative antibiotics. In addition to the unique properties they possess, nanoparticles made from metal oxide are currently attracting considerable attention as possible antibacterials. This research aims to explore the potential anti-biofilm properties of green manufactured ZnO-CuO nanoparticles generated by P. mirabilis. By synthesizing reductive enzymes, bacterial cells can participate in the biosynthesis process. This study explores whether green synthesized ZnO-CuO nanoparticles can work as an anti-biofilm agent formed by P. mirabilis. These nanoparticles were generated using Bacteriocins to determine their effectiveness against bacteria, which were partially purified and showed antimicrobial activity against Gram-negative bacteria of P. mirabilis. AFM, TEM, FESEM, XRD, and ultraviolet (UV)–visible spectroscopy were used to analyze the biosynthesized nanoparticles to ascertain their chemical and physical characteristics. XRD verified the hexagonal structure, TEM demonstrated a size range of 96.00 nm, and FESEM verified the surface morphology. The dispersion and roughness of the nanoparticles are shown through AFM examination. The produced nanoparticles’ UV-visible spectra displayed a maximum peak at 287 and 232 nm. When applied to strains (wild-type) of Proteus mirabilis (multidrug-resistant), copper and zinc nanoparticles had notable biofilm inhibitory effects. Weak biofilm production has been demonstrated by bacteria that effectively generate biofilms, following incubation with 128 μg/mL subminimum inhibitory concentrations (MICs) of CuO nanoparticles for 24 and 48 h at 37 °C. Following treatment with the ZnO-CuO nanocomposite of these strains, downregulation alterations in LuxS expression were detected by utilizing a real-time PCR process. After this, isolates were treated with the nanocomposite, and downregulated shifts in LuxS expression were found by utilizing the real-time PCR technique in contrast with the isolates that were not treated. Zinc oxide (ZnO) nanoparticles can be utilized as antibacterial agents in a concentration-dependent manner, aligning with all observed findings. The present research demonstrates that green synthesized copper oxide–zinc oxide nanocomposites are effective anti-biofilm agents against P. mirabilis. Their noteworthy downregulation of LuxS gene expression successfully prevents biofilm formation and swarming motility. Full article

Pasteurized milk foam has become a quality issue in some applications, such as cappuccino-style drinks, as it should be stable and high-capacity. The extended shelf life of pasteurized milk is also a challenge. Some factors affect the foam capacity and stability; among them, the increasing amount of free fatty acids in raw milk is critical. The psychrotrophic bacteria can produce a lipase-like enzyme, which is responsible for increasing the level of free fatty acids in raw milk. Therefore, this work aims to utilize the cell-free supernatant of a bacteriocin-producing culture as a natural preservative against psychrotrophic and spore-forming bacteria to enhance the foaming capacity and stability and improve the final product’s quality and shelf life. Milk samples from 15 dairy farms were assessed for free fatty acids, microbiological quality, and foaming capacity. Raw milk was divided into four portions: a control without any additive and cell-free supernatant (CFS) treatments, with CFS added at concentrations of 5, 10, and 15 mL/L in each portion. Raw milk was stored for 5 days before heat treatment at 75 °C/30 s, then cooled at 5 °C. All samples were examined for microbiological, free fatty acid, and foaming properties immediately after heat treatment and during storage up to 14 days. The results of this study reveal that there is a negative impact of free fatty acids on the capacity and stability of foaming. The cell-free supernatant (15 mL/L) of the traditional dairy isolate Pediococcus acidilactici inhibits the psychrotrophic bacteria in raw milk during storage for 5 days, a phenomenon which has a direct impact on reducing the free fatty acids, improving the foaming capacity and stability, as well as reducing the bitterness at the end of the shelf life of pasteurized milk up to 14 days compared to the detection of bitterness after 8 days in the control pasteurized milk. It is concluded that, to produce pasteurized milk with a high foaming capacity and extended shelf life, raw milk with low amounts of free fatty acids should be used and fast pasteurized or treated with a bacteriocin of lactic acid bacteria. Full article

Lactic acid bacteria (LAB) are known as producers of various antimicrobial compounds. Among these, bacteriocins have attracted considerable interest because of their potential use as natural food preservatives. The aim of this study was to identify potential strains from Egyptian sources that have unique antibacterial activity for possible future use. In this current study, 835 LAB strains were isolated from different Egyptian sources such as meat, salted fish, chicken byproducts, dairy products, and a starter for fermentation. The bacteriocin activity of cell-free culture supernatants was tested using the spot-on-lawn method against eight indicator strains. As a result, 237 isolates were found to produce bacteriocin-like substances (BLS). According to their antimicrobial spectra, they were classified into three groups: the broad spectrum group (2.1% of isolates), the middle spectrum group (15.2% of isolates), and the narrow spectrum group (82.7% of isolates). 16S rDNA sequencing showed that all isolates belonged to LAB strains such as Lactobacillus, Enterococcus, Carnobacterium, Weissella, and Leuconostoc. Egyptian materials were found to be promising sources of bacteriocin-producing LAB. The BLS generated from LAB in this current work have a diverse antimicrobial spectrum against numerous bacterial hazards, including Listeria. The new strains identified in this study were shown to have characteristic antimicrobial spectra and can be used in the future as effective preservatives in the food industry. Full article

Background: Phage tail-like bacteriocins, or tailocins, provide a competitive advantage to producer cells by killing closely related bacteria. Morphologically similar to headless phages, their narrow target specificity is determined by receptor-binding proteins (RBPs). While RBP engineering has been used to alter the target range of a selected R2 tailocin from Pseudomonas aeruginosa, the process is labor-intensive, limiting broader application. Methods: We introduce a VersaTile-driven R2 tailocin engineering and screening platform to scale up RBP grafting. Results: This platform achieved three key milestones: (I) engineering R2 tailocins specific to Escherichia coli serogroups O26, O103, O104, O111, O145, O146, and O157; (II) reprogramming R2 tailocins to target, for the first time, the capsule and a new species, specifically the capsular serotype K1 of E. coli and K11 and K63 of Klebsiella pneumoniae; (III) creating the first bivalent tailocin with a branched RBP and cross-species activity, effective against both E. coli K1 and K. pneumoniae K11. Over 90% of engineered tailocins were effective, with clear pathways for further optimization identified. Conclusions: This work lays the groundwork for a scalable platform for the development of engineered tailocins, marking an important step towards making R2 tailocins a practical therapeutic tool for targeted bacterial infections. Full article

Reducing the use of antibiotics in animal husbandry is essential to limit the spread of resistance. A promising alternative to antibiotics resides in bacteriocins, which are antimicrobial peptides produced by bacteria showing a great diversity in terms of spectrum of activity, structure, and mechanism of action. In this study, the effects of diverse bacteriocins on the composition and metabolic activity of chicken cecal microbiota were examined in vitro, in comparison with antibiotics. Different impacts on microbiota composition were revealed by 16S metabarcoding, with colistin having the most dramatic impact on diversity. Bacteriocins produced by Gram-negative bacteria, microcins J25 and E492, did not significantly influence the microbiota composition. In contrast, bacteriocins from Gram-positive bacteria impacted the abundance of lactic acid bacteria, with nisin Z showing the most impact while pediocin PA-1 (M31L) exhibited a moderate effect at the highest concentration tested. This study emphasizes the potential of bacteriocins as alternatives to antibiotics in poultry to protect from pathogens such as Salmonella, Clostridium, and Enterococcus. Full article