Obtaining an Ent35-MccV derivative with mutated hinge region that exhibits increased activity against Listeria monocytogenes and Escherichia coli

Impact of bacteriocin-producing strains on bacterial community composition in a simplified human intestinal microbiota

Bacteriocins are antimicrobial peptides that have been studied for decades as food bio-preservatives or as alternatives to antibiotics. They also have potential as modulators of the gut microbiome, which has been linked to human health. However, it is difficult to predict a priori how bacteriocins will impact complex microbial communities through direct and indirect effects. Here we assess the effect of different bacteriocin-producing strains on a Simplified Human Intestinal Microbiota (SIHUMI) model, using a set of bacteriocin-producing strains (Bac+) and otherwise isogenic non-producers (Bac-). Bacteriocins from different classes and with different activity spectra were selected, including lantibiotics such as lacticin 3147 and nisin A, and pediocin-like bacteriocins such as pediocin PA-1 among other peptides. SIHUMI is a bacterial consortium of seven diverse human gut species that assembles to a predictable final composition in a particular growth medium. Each member can be individually tracked by qPCR. Bac+ and Bac- strains were superimposed on the SIHUMI system, and samples were taken at intervals up to 48 h. The genome copy number of each SIHUMI member was evaluated using specific primers. We establish that the composition of the community changes in response to the presence of either broad- or narrow-spectrum bacteriocin producers and confirm that there are significant off-target effects. These effects were analyzed considering antagonistic inter-species interactions within the SIHUMI community, providing a comprehensive insight into the possible mechanisms by which complex communities can be shaped by bacteriocins.

Single strain control of microbial consortia

The scope of bioengineering is expanding from the creation of single strains to the design of microbial communities, allowing for division-of-labour, specialised sub-populations and interaction with “wild” microbiomes. However, in the absence of stabilising interactions, competition between microbes inevitably leads to the removal of less fit community members over time. Here, we leverage amensalism and competitive exclusion to stabilise a two-strain community by engineering a strain of Escherichia coli which secretes a toxin in response to competition. We show experimentally and mathematically that such a system can produce stable populations with a composition that is tunable by easily controllable parameters. This system creates a tunable, stable two-strain consortia while only requiring the engineering of a single strain.

Engineered microbial communities can divide labour between their members and interface with natural microbiomes. Here the authors demonstrate how a single toxin producing engineered strain can tune the composition of a two-strain community.

Features and applications of Ent35-MccV hybrid bacteriocin: current state and perspectives

Bacteriocins are peptides of ribosomal synthesis that are active against bacteria related to the producing strain. They have been widely used in the food industry as biopreservatives. The generation of hybrid peptides by combining the genes that encode two different bacteriocins has made it possible to study the mechanisms of action of the bacteriocins that compose them and also develop new peptides with improved biotechnological applications. Hybrid bacteriocins may be obtained in several ways. In our laboratory, by combining enterocin CRL35 and microcin V (Ent35-MccV), we obtained a broad-spectrum peptide that is active against both Gram-positive and Gram-negative bacteria. Ent35-MccV is sensitive to the action of intestinal proteases and is heat resistant, which makes it a good candidate for use as a biopreservative. For this reason, the peptide was tested in skim milk and beef burgers as food models. We also obtained more potent variants of the hybrid by modifying the central amino acid of the hinge region that connects the two bacteriocins. This review also discusses future applications and perspectives regarding the Ent35-MccV and other hybrid peptides.Key Points• Ent35-MccV is a new broad-spectrum bacteriocin.• The mechanism of action of bacteriocins can be studied using hybrid peptides.• Genetic engineering allows obtaining improved bacteriocin derivatives.• Hybrid peptides can be used in the food, pharmaceutical, and veterinary applications.