Abstract
Bacteriocins are antimicrobial peptides/proteins that can have narrow or broad inhibitory spectra and remarkable potency against clinically relevant pathogens. One such bacteriocin that is extensively used in the food industry and with potential for biotherapeutic application is the post-translationally modified peptide, nisin. Recent studies have shown the impact of nisin on the gastrointestinal microbiome, but relatively little is known of how abundant nisin production is in nature, the breadth of existing variants, and their antimicrobial potency. Whether or not nisin production and immunity are widespread in gut microbiomes could be a deciding factor in determining the suitability of nisin as a prospective therapeutic for human and/or animal infections. Here, we used publicly available data sets to determine the presence of widespread and diverse nisin biosynthetic gene clusters (nBGCs) across the biosphere. We show that 30% of these nBGCs are predicted to be located on mobile genetic elements, with some found in pathogenic bacteria. Furthermore, we highlight evidence of horizontal gene transfer of nBGCs between genera, including Streptococcus suis, Enterococcus hirae, and Staphylococcus aureus. In all, we describe 107 novel nisin-like peptides. Five representatives were heterologously expressed and all exhibited antimicrobial activity. We further characterized nisin VP, a novel natural nisin variant produced by Velocimicrobium porci isolated from the porcine gut. The peptide has a completely novel hinge region "AIQ" not detected in other nisin variants to date. While nisin VP could be induced by nisin A, the latter could not be induced by nisin VP.IMPORTANCEOur research reveals the heretofore underappreciated presence of diverse and widespread nisin-like biosynthetic gene clusters in microbiomes across the globe. Notably, different clusters share similar biosynthetic machinery but differ in sequence, suggesting gene transfer and adaptation. We identify >100 new nisin-like variants, including several in species not previously known to produce nisin. This emphasizes the widespread dissemination of nisin-like gene clusters and the diversity of novel core peptides with biotherapeutic potential. These findings point to a role for nisin in microbial competition in microbiomes. We heterologously expressed nine nisin variants, five of which are completely novel peptides, using the nisin A biosynthetic machinery and confirmed that all exhibited antimicrobial activity.