Compatibility, Cytotoxicity, and Gastrointestinal Tenacity of Bacteriocin-Producing Bacteria Selected for a Consortium Probiotic Formulation to Be Used in Livestock Feed

Bacteriocin-Producing Staphylococci and Mammaliicocci Strains for Agro-Food and Public Health Applications with Relevance of Micrococcin P1

Antimicrobial-producing strains and their bacteriocins hold great promise for the control of bacterial diseases, being an attractive alternative to antibiotics. Thus, the aim of this study was to evaluate the inhibitory activity of 15 bacteriocin-producing staphylococci and mammaliicocci (BP-S/M) strains and their pre-purified extracts with butanol (BT) against a collection of 27 harmful or zoonotic strains (including Gram-positive/-negative bacteria and molds) with relevance in the public health and agro-food fields. These indicators (excluding Gram-negative strains) were grouped into seven categories based on their potential application areas: dairy livestock mastitis, avian pathogen zoonoses, swine zoonoses, food safety, aquaculture, wine making, and mushroom cultivation. In addition, cross-immunity assays between the BP-S/M strains were carried out to identify potential strain combinations to enhance their activity against pathogens. Finally, the hemolytic and gelatinase activities were tested in the BP-S/M strains. A strong inhibitory capacity of the BP-S/M strains was verified against relevant Gram-positive indicators, such as methicillin-resistant Staphylococcus aureus, Listeria monocytogenes, and Clostridium perfringens, among others, while no activity was detected against Gram-negative ones. Interestingly, several BT extracts inhibited the two mold indicators included in this study as representants of mushroom pathogens. The Micrococcin P1 producer Staphylococcus hominis C5835 (>60% of indicators were intensively inhibited by all the methods) can be proposed as a potential candidate for the control of bacterial diseases in the aforementioned categories alone or in combination with other BP-S/M strains (mainly with Staphylococcus warneri X2969). In this regard, five potential combinations of BP-S/M strains that enhanced their activity against specific pathogens were detected.

Classification and Multi-Functional Use of Bacteriocins in Health, Biotechnology, and Food Industry

Bacteriocins is the name given to products of the secondary metabolism of many bacterial genera that must display antimicrobial activity. Although there are several bacteriocins described today, it has not been possible to reach a consensus on the method of classification for these biomolecules. In addition, many of them are not yet authorized for therapeutic use against multi-drug-resistant microorganisms due to possible toxic effects. However, recent research has achieved considerable progress in the understanding, classification, and elucidation of their mechanisms of action against microorganisms, which are of medical and biotechnological interest. Therefore, in more current times, protocols are already being conducted for their optimal use, in the hopes of solving multiple health and food conservation problems. This review aims to synthetize the information available nowadays regarding bacteriocins, and their classification, while also providing an insight into the future possibilities of their usage for both the pharmaceutical, food, and biotechnological industry.

The Role of Probiotics in Improving Food Safety: Inactivation of Pathogens and Biological Toxins

Currently, many advances have been made in avoiding food contamination by numerous pathogenic and toxigenic microorganisms. Many studies have shown that different probiotics, in addition to having beneficial effects on the host's health, have a very good ability to eliminate and neutralize pathogens and their toxins in foods which leads to enhanced food safety. The present review purposes to comprehensively discuss the role of probiotics in improving food safety by inactivating pathogens (bacterial, fungal, viral, and parasite agents) and neutralizing their toxins in food products. Some recent examples in terms of the anti-microbial activities of probiotics in the body after consuming contaminated food have also been mentioned. This review shows that different probiotics have the potential to inactivate pathogens and neutralize and detoxify various biological agents in foods, as well as in the host body after consumption.

Structure of Lacticaseicin 30 and Its Engineered Variants Revealed an Interplay between the N-Terminal and C-Terminal Regions in the Activity against Gram-Negative Bacteria

Lacticaseicin 30 is one of the five bacteriocins produced by the Gram-positive Lacticaseibacillus paracasei CNCM I-5369. This 111 amino acid bacteriocin is noteworthy for being active against Gram-negative bacilli including Escherichia coli strains resistant to colistin. Prediction of the lacticaseicin 30 structure using the Alphafold2 pipeline revealed a largely helical structure including five helix segments, which was confirmed by circular dichroism. To identify the structural requirements of the lacticaseicin 30 activity directed against Gram-negative bacilli, a series of variants, either shortened or containing point mutations, was heterologously produced in Escherichia coli and assayed for their antibacterial activity against a panel of target strains including Gram-negative bacteria and the Gram-positive Listeria innocua. Lacticaseicin 30 variants comprising either the N-terminal region (amino acids 1 to 39) or the central and C-terminal regions (amino acids 40 to 111) were prepared. Furthermore, mutations were introduced by site-directed mutagenesis to obtain ten bacteriocin variants E6G, T7P, E32G, T33P, T52P, D57G, A74P, Y78S, Y93S and A97P. Compared to lacticaseicin 30, the anti-Gram-negative activity of the N-terminal peptide and variants E32G, T33P and D57G remained almost unchanged, while that of the C-terminal peptide and variants E6G, T7P, T52P, A74P, Y78S, Y93S and A97P was significantly altered. Finally, the N-terminal region was further shortened to keep only the first 20 amino acid part that was predicted to include the first helix. The anti-Gram-negative activity of this truncated peptide was completely abolished. Overall, this study shows that activity of lacticaseicin 30, one of the rare Gram-positive bacteriocins inhibiting Gram-negative bacteria, requires at least two helices in the N-terminal region and that the C-terminal region carries amino acids playing a role in modulation of the activity. Taken together, these data will help to design forthcoming variants of lacticaseicin 30 as promising therapeutic agents to treat infections caused by Gram-negative bacilli.

The gut commensal bacterium Enterococcus faecalis LX10 contributes to defending against Nosema bombycis infection in Bombyx mori

BACKGROUND

Microsporidia, a group of obligate intracellular fungal-related parasites, have been used as efficient biocontrol agents for agriculture and forestry pests due to their host specificity and transovarial transmission. They mainly infect insect pests through the intestinal tract, but the interactions between microsporidia and the gut microbiota of the host have not been well demonstrated.

RESULTS

Based on the microsporidia-Bombyx mori model, we report that the susceptibility of silkworms to exposure to the microsporidium Nosema bombycis was both dose and time dependent. Comparative analyses of the silkworm gut microbiome revealed substantially increased abundance of Enterococcus belonging to Firmicutes after N. bombycis infection. Furthermore, a bacterial strain (LX10) was obtained from the gut of B. mori and identified as Enterococcus faecalis based on 16S rRNA sequence analysis. E. faecalis LX10 reduced the N. bombycis spore germination rate and the infection efficiency in vitro and in vivo, as confirmed by bioassay tests and histopathological analyses. In addition, after simultaneous oral feeding with E. faecalis LX10 and N. bombycis, gene (Akirin, Cecropin A, Mesh, Ssk, DUOX and NOS) expression, hydrogen peroxide and nitric oxide levels, and glutathione S-transferase (GST) activity showed different degrees of recovery and correction compared with those under N. bombycis infection alone. Finally, the enterococcin LX protein was identified from sterile LX10 fermentation liquid based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis.

CONCLUSION

Altogether, the results revealed that E. faecalis LX10 with anti-N. bombycis activity might play an important role in protecting silkworms from microsporidia. Removal of these specific commensal bacteria with antibiotics and utilization of transgenic symbiotic systems may effectively improve the biocontrol value of microsporidia. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Bacteriocin-Like Inhibitory Substances in Staphylococci of Different Origins and Species With Activity Against Relevant Pathogens

Bacteriocins are antimicrobial peptides with relevance in the modulation of human and animal microbiota that have gained interest in biomedical and biotechnological applications. In this study, the production of bacteriocin-like inhibitory substances (BLIS) was tested among a collection of 890 staphylococci of different origins (humans, animals, food, and the environment) and species, both coagulase-positive (CoPS, 238 isolates of 3 species) and coagulase-negative staphylococci (CoNS, 652 isolates of 26 species). Of the 890 staphylococci, 60 (6.7%) showed antimicrobial activity by the spot-on-lawn method against at least one of the 25 indicator bacteria tested. BLIS-producer (BLIS⁺) isolates were detected in 8.8% of CoPS and 6.0% of CoNS. The staphylococcal species with the highest percentages of BLIS⁺ isolates were S. chromogenes (38.5%), S. pseudintermedius (26.7%), and S. warneri (23.1%). The production of BLIS was more frequently detected among isolates of pets, wild animals, and food. Moreover, 13 BLIS⁺ isolates showed wide antimicrobial activiy spectrum, and 7 of these isolates (of species S. aureus, S. pseudintermedius, S. sciuri, and S. hominis) demonstrated antimicrobial activity against more than 70% of the indicator bacteria tested. The genetic characterization (by PCR and sequencing) of the 60 BLIS⁺ isolates revealed the detection of (a) 11 CoNS and CoPS isolates carrying putative lantibiotic-like genes; (b) 3 S. pseudintermedius isolates harboring the genes of BacSp222 bacteriocin; and (c) 2 S. chromogenes isolates that presented the gene of a putative cyclic bacteriocin (uberolysin-like), being the first report in this CoNS species. Antimicrobial susceptibility testing was performed in BLIS⁺ isolates and one-third of the CoNS isolates showed susceptibility to all antibiotics tested, which also lacked the virulence genes studied. These BLIS⁺ CoNS are good candidates for further characterization studies.

Pediococcus pentosaceus, a future additive or probiotic candidate

Background

Pediococcus pentosaceus, a promising strain of lactic acid bacteria (LAB), is gradually attracting attention, leading to a rapid increase in experimental research. Due to increased demand for practical applications of microbes, the functional and harmless P. pentosaceus might be a worthwhile LAB strain for both the food industry and biological applications.

Results

As an additive, P. pentosaceus improves the taste and nutrition of food, as well as the storage of animal products. Moreover, the antimicrobial abilities of Pediococcus strains are being highlighted. Evidence suggests that bacteriocins or bacteriocin-like substances (BLISs) produced by P. pentosaceus play effective antibacterial roles in the microbial ecosystem. In addition, various strains of P. pentosaceus have been highlighted for probiotic use due to their anti-inflammation, anticancer, antioxidant, detoxification, and lipid-lowering abilities.

Conclusions

Therefore, it is necessary to continue studying P. pentosaceus for further use. Thorough study of several P. pentosaceus strains should clarify the benefits and drawbacks in the future.

In silico analyses of the genomes of three new bacteriocin-producing bacteria isolated from animal's faeces

Here, we have analysed and explored the genome sequences of three newly isolated bacteria that were recently characterised for their probiotic activities and ability to produce bacteriocins. These strains, isolated from faeces of animals living in captivity at the zoological garden of Lille (France), are Escherichia coli ICVB443, Enterococcus faecalis ICVB501 and Pediococcus pentosaceus ICVB491. Their genomes have been analysed and compared to those of their pathogenic or probiotic counterparts. The genome analyses of E. coli ICVB443 and Ent. faecalis ICVB501 displayed similarities to those of probiotics E. coli 1917 Nissle, and Ent. faecalis Symbioflor 1, respectively. Furthermore, E. coli ICVB443 shares at least 89 genes with the enteroaggregative E. coli 55989 (EAEC), and Ent. faecalis ICVB501 shares at least 315 genes with the pathogenic Ent. faecalis V583 strain. Unlike Ped. pentosaceus ICVB491, which is devoid of virulence genes, E. coli ICVB443 and Ent. faecalis ICVB501 both carry genes encoding virulence factors on their genomes. Of note, the bioinformatics analysis of these two genomes located the bsh gene, which codes for bile salt hydrolase (BSH). The presence of BSH is of major importance, as it can help to increase the viability of these two strains in the gastrointestinal tract (GIT). The genome analysis of Ped. pentosaceus ICVB491 confirmed its GRAS status (Generally Recognised As Safe), as no genomic virulence factor determinant was found.