Synergistic Inhibition of Plantaricin E/F and Lactic Acid Against Aeromonas hydrophila LPL-1 Reveals the Novel Potential of Class IIb Bacteriocin

Lactic acid bacteria as an eco-friendly approach in plant production: Current state and prospects

Since the late nineteenth century, the agricultural sector has experienced a tremendous increase in chemical use in response to the growing population. Consequently, the intensive and indiscriminate use of these substances caused serious damage on several levels, including threatening human health, disrupting soil microbiota, affecting wildlife ecosystems, and causing groundwater pollution. As a solution, the application of microbial-based products presents an interesting and ecological restoration tool. The use of Plant Growth-Promoting Microbes (PGPM) affected positive production, by increasing its efficiency, reducing production costs, environmental pollution, and chemical use. Among these microbial communities, lactic acid bacteria (LAB) are considered an interesting candidate to be formulated and applied as effective microbes. Indeed, these bacteria are approved by the European Food Safety Authority (EFSA) and Food and Drug Administration (FDA) as Qualified Presumption of Safety statute and Generally Recognized as Safe for various applications. To do so, this review comes as a road map for future research, which addresses the different steps included in LAB formulation as biocontrol, bioremediation, or plant growth promoting agents from the isolation process to their field application passing by the different identification methods and their various uses. The plant application methods as well as challenges limiting their use in agriculture are also discussed.

Improving the Efficiency of Viability-qPCR with Lactic Acid Enhancer for the Selective Detection of Live Pathogens in Foods

Pathogenic Escherichia coli are the most prevalent foodborne bacteria, and their accurate detection in food samples is critical for ensuring food safety. Therefore, a quick technique named viability-qPCR (v-qPCR), which is based on the ability of a selective dye, such as propidium monoazide (PMA), to differentiate between alive and dead cells, has been developed. Despite diverse, successful applications, v-qPCR is impaired by some practical limitations, including the ability of PMA to penetrate the outer membrane of dead Gram-negative bacteria. The objective of this study is to evaluate the ability of lactic acid (LA) to improve PMA penetration and, thus, the efficiency of v-qPCR in detecting the live fraction of pathogens. The pre-treatment of E. coli ATCC 8739 cells with 10 mM LA greatly increased PMA penetration into dead cells compared to conventional PMA-qPCR assay, avoiding false positive results. The limit of detection when using LA-PMA qPCR is 1% viable cells in a mixture of dead and alive cells. The optimized LA-PMA qPCR method was reliably able to detect log 2 CFU/mL culturable E. coli in milk spiked with viable and non-viable bacteria. Lactic acid is cheap, has low toxicity, and can be used to improve the efficiency of the v-qPCR assay, which is economically interesting for larger-scale pathogen detection applications intended for food matrices.

Comparative genomics of four lactic acid bacteria identified with Vitek MS (MALDI-TOF) and whole-genome sequencing

Lactic acid bacteria (LAB) can be used as a probiotic or starter culture in dairy, meat, and vegetable fermentation. Therefore, their isolation and identification are essential. Recent advances in omics technologies and high-throughput sequencing have made the identification and characterization of bacteria. This study firstly aimed to demonstrate the sensitivity of the Vitek MS (MALDI-TOF) system in the identification of lactic acid bacteria and, secondly, to characterize bacteria using various bioinformatics approaches. Probiotic potency-related genes and secondary metabolite biosynthesis gene clusters were examined. The Vitek MS (MALDI-TOF) system was able to identify all of the bacteria at the genus level. According to whole genome sequencing, the bacteria were confirmed to be Lentilactobacillus buchneri, Levilactobacillus brevis, Lactiplantibacillus plantarum, Levilactobacillus namurensis. Bacteria had most of the probiotic potency-related genes, and different toxin-antitoxin systems such as PemIK/MazEF, Hig A/B, YdcE/YdcD, YefM/YoeB. Also, some of the secondary metabolite biosynthesis gene clusters, some toxic metabolite-related genes, and antibiotic resistance-related genes were detected. In addition, Lentilactobacillus buchneri Egmn17 had a type II-A CRISPR/Cas system. Lactiplantibacillus plantarum Gmze16 had a bacteriocin, plantaricin E/F.

Unraveling the antimicrobial potential of Lactiplantibacillus plantarum strains TE0907 and TE1809 sourced from Bufo gargarizans: advancing the frontier of probiotic-based therapeutics

Introduction

In an era increasingly defined by the challenge of antibiotic resistance, this study offers groundbreaking insights into the antibacterial properties of two distinct Lactiplantibacillus plantarum strains, TE0907 and TE1809, hailing from the unique ecosystem of Bufo gargarizans. It uniquely focuses on elucidating the intricate components and mechanisms that empower these strains with their notable antibacterial capabilities.

Methods

The research employs a multi-omics approach, including agar diffusion tests to assess antibacterial efficacy and adhesion assays with HT-29 cells to understand the preliminary mechanisms. Additionally, gas chromatography-mass spectrometry (GC-MS) is employed to analyze the production of organic acids, notably acetic acid, and whole-genome sequencing is utilized to identify genes linked to the biosynthesis of antibiotics and bacteriocin-coding domains.

Results

The comparative analysis highlighted the exceptional antibacterial efficacy of strains TE0907 and TE1809, with mean inhibitory zones measured at 14.97 and 15.98 mm, respectively. A pivotal discovery was the significant synthesis of acetic acid in both strains, demonstrated by a robust correlation coefficient (cor ≥ 0.943), linking its abundance to their antimicrobial efficiency. Genomic exploration uncovered a diverse range of elements involved in the biosynthesis of antibiotics similar to tetracycline and vancomycin and potential regions encoding bacteriocins, including Enterolysin and Plantaricin.

Conclusion

This research illuminates the remarkable antibacterial efficacy and mechanisms intrinsic to L. plantarum strains TE0907 and TE1809, sourced from B. gargarizans. The findings underscore the strains' extensive biochemical and enzymatic armamentarium, offering valuable insights into their role in antagonizing enteric pathogens. These results lay down a comprehensive analytical foundation for the potential clinical deployment of these strains in safeguarding animal gut health, thereby enriching our understanding of the role of probiotic bacteria in the realm of antimicrobial interventions.

Administration of probiotics affects Artemia franciscana metanauplii intestinal ultrastructure and offers resistance against a Photobacterium damselae ssp. piscicida induced oxidative stress response

The effects of Photobacterium damselae ssp. piscicida (Phdp) on immune responses and intestinal ultrastructure of Artemia franciscana following infection and their amelioration by the probiotic bacteria Bacillus subtilis, Lactobacillus plantarum and Lactococcus lactis were evaluated. Pathogen growth inhibition in coculture with each probiotic and its virulence against Artemia were confirmed with an LC50 of 105 CFU mL-1. Phdp administration to Artemia at sublethal levels resulted in depletion of superoxide dismutase, glutathione reductase, glutathione transferase and phenoloxidase activities, extensive lipid peroxidation and reduced survival. Following a combined administration of each probiotic and the pathogen, enzyme activities and survival were significantly higher, while lipid peroxidation was reduced, compared to the infected group with no probiotic treatment (P < 0.05). The transmission electron microscopy study revealed that pathogen infection resulted in disarranged and fragmented microvilli, formation of empty or pathogen containing cytoplasmic vacuoles and damaged mitochondria. In the probiotic-treated and Phdp-infected series, intestinal cells showed normal appearance, except for the presence of pathogen-containing vacuoles and highly ordered but laterally stacked microvilli. The results of the present study indicate that Phdp induces cell death through an oxidative stress response and probiotics enhance Artemia immune responses to protect it against the Phdp induced damage.

Antimicrobial activity of Lactiplantibacillus plantarum against shiga toxin-producing Escherichia coli

AIMS

The aim of the present work was to characterize the Lactiplantibacillus sp. LP5 strain, isolated from pork production, and identify bacteriocin-like inhibitory substances produced by this strain.

METHODS AND RESULTS

In this study, LP5 was identified by species-specific PCR and 16S rRNA sequencing. Additionally, bacterial growth kinetics, antimicrobial activity, the detection of genes related to plantaricin production, and the genetic expression of plantaricins were determined. Lactiplantibacillus sp. LP5 was identified as Lactiplantibacillus plantarum. The well-diffusion test using cell-free supernatants (CFS), neutralized CFS, CFS treated with catalase, and CFS treated with proteinase K showed that inhibitory effects on a Shiga toxin-producing Escherichia coli (STEC) strain were produced by bacteriocins. The PCR technique allowed the detection of genes encoding E/F plantaricins, as well as J/K and whole genome sequencing, and bacteriocin mining analysis allowed us to confirm the presence of these plantaricins.

CONCLUSIONS

We can conclude that the inhibitory effect of L. plantarum LP5 isolated from pigs against the STEC EDL933 strain could be associated with the bacteriocins production and represents a potential use as a probiotic strain.

Effect of lactic acid bacteria on the structure and potential function of the microbial community of Nongxiangxing Daqu

OBJECTIVES

The microbial community structure of the saccharifying starter, Nongxiangxing Daqu(Daqu), is a crucial factor in determining Baijiu's quality. Lactic acid bacteria (LAB), are the dominant microorganisms in the Daqu. The present study investigated the effects of LAB on the microbial community structure and its contribution to microbial community function during the fermentation of Daqu.

METHODS

The effect of LAB on the structure and function of the microbial community of Daqu was investigated using high-throughput sequencing technology combined with multivariate statistical analysis.

RESULTS

LAB showed a significant stage-specific evolution pattern during Daqu fermentation. The LEfSe analysis and the random forest learning algorithm identified LAB as vital differential microorganisms during Daqu fermentation. The correlation co-occurrence network showed aggregation of LAB and Daqu microorganisms, indicating LAB's significant position in influencing the microbial community structure, and suggests that LAB showed negative correlations with Bacillus, Saccharopolyspora, and Thermoactinomyces but positive correlations with Issatchenkia, Candida, Acetobacter, and Gluconobacter. The predicted genes of LAB enriched 20 functional pathways during Daqu fermentation, including Biosynthesis of amino acids, Alanine, aspartate and glutamate metabolism, Valine, leucine and isoleucine biosynthesis and Starch and sucrose metabolism, which suggested that LAB had the functions of polysaccharide metabolism and amino acid biosynthesis.

CONCLUSION

LAB are important in determining the composition and function of Daqu microorganisms, and LAB are closely related to the production of nitrogenous flavor substances in Daqu. The study provides a foundation for further exploring the function of LAB and the regulation of Daqu quality.

Palmatine Inhibits the Pathogenicity of Aeromonas hydrophila by Reducing Aerolysin Expression

Aeromonas hydrophila, an opportunistic aquatic pathogen widely spread in aquatic environments, is responsible for a number of infectious diseases in freshwater aquaculture. In addition, A. hydrophila can transmit from diseased fish to humans and results in health problems. The occurrence of antibiotic-resistant bacterial strains restricts the application of antibiotics and is responsible for failure of the treatment. Moreover, residues of antibiotics in aquatic products often threaten the quality and safety. Therefore, alternative strategies are called to deal with infections caused by antibiotic-resistant bacteria. Aerolysin, one of the most important virulence factors of A. hydrophila, is adopted as a unique anti-virulence target on the basis of the anti-virulence strategy to battling infections caused by A. hydrophila. Palmatine, an isoquinoline alkaloid from a variety of herbal medicines that showed no anti-A. hydrophila activity, could reduce hemolysis of the bacterium by decreasing aerolysin production. The results of the qPCR assay demonstrated that the transcription of the aerA gene was suppressed. Moreover, cell viability and in vivo study showed that palmatine treatment could decrease the pathogenicity of A. hydrophila both in vitro and in vivo. In summary, palmatine is a leading compound against A. hydrophila-associated infection in aquaculture by inhibiting the expression of aerolysin.