Cell Wall-active Bacteriocins and Their Applications Beyond Antibiotic Activity

Structural and biosynthetic diversity of plantaricins from Lactiplantibacillus

Lactiplantibacillus plantarum (L. plantarum) produces an antimicrobial peptide known as plantaricin. Plantaricin-producing L. plantarum is of interest for its gut-friendly nature, wide range of sugar utilization, palatability, and probiotic attributes, making it a better candidate for the food industry. Numerous strains of plantaricin-producing L. plantarum have been isolated from different ecological niches and found to follow different mechanisms for plantaricin production. The mechanism of plantaricin production is sensitive to environmental factors; therefore, any alteration in the optimum conditions can inhibit/halt bacteriocin production. To regain the lost or hidden plantaricin-producing character of the L. plantarum strains under ideal laboratory conditions, it is essential to understand the mechanism of plantaricin production. Previously, discrete information on various mechanisms of plantaricin production has been elaborated. However, based on the literature analysis, we observed that a systematic classification of plantaricins produced by L. plantarum is not explored. Hence, we aim to collect information about rapidly emerging plantaricins and distribute them among the different classes of bacteriocin, followed by classifying them based on different mechanisms of plantaricin production. This may help scaleup the bacteriocin production at industrial levels, which is otherwise challenging to achieve. This will also help the reader understand plantaricins and their mechanism of plantaricin production to a deeper extent and to characterize/reproduce the peptide where plantaricin production is a hidden character. KEY POINTS: • L. plantarum produces the antimicrobial compound plantaricin. • L. plantarum has different regulatory operons which control plantaricin production. • Based on the regulatory operon, the mechanism of plantaricin production is different.

The Complex Role of Lactic Acid Bacteria in Food Detoxification

Toxic ingredients in food can lead to serious food-related diseases. Such compounds are bacterial toxins (Shiga-toxin, listeriolysin, Botulinum toxin), mycotoxins (aflatoxin, ochratoxin, zearalenone, fumonisin), pesticides of different classes (organochlorine, organophosphate, synthetic pyrethroids), heavy metals, and natural antinutrients such as phytates, oxalates, and cyanide-generating glycosides. The generally regarded safe (GRAS) status and long history of lactic acid bacteria (LAB) as essential ingredients of fermented foods and probiotics make them a major biological tool against a great variety of food-related toxins. This state-of-the-art review aims to summarize and discuss the data revealing the involvement of LAB in the detoxification of foods from hazardous agents of microbial and chemical nature. It is focused on the specific properties that allow LAB to counteract toxins and destroy them, as well as on the mechanisms of microbial antagonism toward toxigenic producers. Toxins of microbial origin are either adsorbed or degraded, toxic chemicals are hydrolyzed and then used as a carbon source, while heavy metals are bound and accumulated. Based on these comprehensive data, the prospects for developing new combinations of probiotic starters for food detoxification are considered.

Effects of drinking water supplementation with Lactobacillus reuteri, and a mixture of reuterin and microcin J25 on the growth performance, caecal microbiota and selected metabolites of broiler chickens

Background

Since the overuse of antibiotics in animal production has led to a selection of antibiotic-resistant pathogens that affect humans and animals as well. Scientists are therefore searching for novel natural alternatives to antibiotics. In this study Lactobacillus reuteri and a combination of reuterin and microcin J25 (RJ) were evaluated as promoters of growth and modulators of the cecal microbiota and metabolite profiles in broiler chickens. One-day-old Cobb 500 male broilers were distributed to 8 treatments: negative control (without antibiotic), positive control (bacitracin), three concentrations of RJ and three doses of L. reuteri plus glycerol. The birds (2176, 34 per pen, 8 pens per treatment) were reared for 35 d.

Results

The body weight of the bacitracin and 5 mmol/L reuterin combined with 0.08 μmol/L microcin J25 (10RJ) treatment group was significantly higher than that of the negative control group (P < 0.05). L. reuteri had no significant effect on broiler growth. MiSeq high-throughput sequencing of 16S rRNA showed clustering of cecal microbial operational taxonomic unit diversity according to treatment. The influence of bacitracin and 10RJ on bacterial community overall structure was similar. They promoted Ruminococcaceae, Lachnospiraceae and Lactobacillaceae, increased the relative abundance of Faecalibacterium and decreased the abundance of Bacteroides and Alistipes, while the negative control condition favored Bacteroidaceae and Rikenellaceae. Furthermore, 10RJ increased the concentration of short-chain fatty acid in the cecum and changed the metabolome overall.

Conclusions

These overall suggest that 10RJ can promote a host-friendly gut environment by changing the cecal microbiome and metabolome. This combination of natural antimicrobial agents in the drinking water had a positive effect on broiler growth and may be suitable as an alternative to antibiotic growth promoters.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00683-6.

Bacteriocins: Properties and potential use as antimicrobials

A variety of bacteriocins originate from lactic acid bacteria, which have recently been modified by scientists. Many strains of lactic acid bacteria related to food groups could produce bacteriocins or antibacterial proteins highly effective against foodborne pathogens such as Staphylococcus aureus, Pseudomonas fluorescens, P. aeruginosa, Salmonella typhi, Shigella flexneri, Listeria monocytogenes, Escherichia coli O157:H7, and Clostridium botulinum. A wide range of bacteria belonging primarily to the genera Bifidobacterium and Lactobacillus have been characterized with different health‐promoting attributes. Extensive studies and in‐depth understanding of these antimicrobials mechanisms of action could enable scientists to determine their production in specific probiotic lactic acid bacteria, as they are potentially crucial for the final preservation of functional foods or for medicinal applications. In this review study, the structure, classification, mode of operation, safety, and antibacterial properties of bacteriocins as well as their effect on foodborne pathogens and antibiotic‐resistant bacteria were extensively studied.

Inhibitory Activity of Natural Synergetic Antimicrobial Consortia Against Salmonella enterica on Broiler Chicken Carcasses

The currently most utilized antimicrobial agent in poultry processing facilities is peracetic acid, a chemical increasingly recognized as hazardous to human health. We evaluated the efficacy of mixtures of natural antimicrobial compounds, namely reuterin, microcin J25, and lactic acid, for reducing the viability of Salmonella enterica and total aerobes on broiler chicken carcasses. The compounds were compared singly and in combination with water and 0.1% peracetic acid. The minimum inhibitory concentrations of reuterin, lactic acid, and microcin J25 against S. enterica serovar Enteritidis were respectively 2 mM, 0.31%, and 0.03 μM. In vitro, the combinations of reuterin + lactic acid and reuterin + microcin J25 were synergic, making these compounds effective at four times lower concentrations than those used alone. Salmonella viable counts fell to zero within 10 min of contact with reuterin + lactic acid at 10 times the concentrations used in combination, compared to 18 h in the case of reuterin + microcin J25. Sprayed onto chilled chicken carcasses, this reuterin + lactic acid mixture reduced Salmonella spp. counts by 2.02 Log CFU/g, whereas reuterin + microcin J25 and peracetic acid reduced them by respectively 0.83 and 1.13 Log CFU/g. The synergy of reuterin with lactic acid or microcin J25 as inhibitors of bacterial growth was significant. Applied as post-chill spray, these mixtures could contribute to food safety by decreasing Salmonella counts on chicken carcasses.

Purification and Characterization of Pasteuricin Produced by Staphylococcus pasteuri RSP-1 and Active against Multidrug-Resistant Staphylococcus aureus

Staphylococcus aureus is an important pathogen implicated in various diseases, including staphylococcal food poisoning. Bacteriocins are considered safe and effective antimicrobial substances for the prevention of the growth of pathogenic bacteria. In this article, we describe the purification and characterization of pasteuricin, a novel bacteriocin produced by Staphylococcus pasteuri RSP-1. A cell-free supernatant of S. pasteuri RSP-1 exerted strong antimicrobial activity against staphylococci, including methicillin-resistant S. aureus (MRSA), and gram-positive bacteria. The loss of antimicrobial activity upon treatment with proteolytic enzymes confirmed the proteinaceous nature of pasteuricin. A rapid and pronounced bactericidal effect of pasteuricin was confirmed by a live-dead bacterial viability assay. To our knowledge, pasteuricin is the first reported S. pasteuri bacteriocin that inhibits S. aureus. Because pasteuricin is characterized by strong antimicrobial activity and high stability, it has potential as an alternative antimicrobial agent to antibiotics.