A novel bacteriocin produced by Bifidobacterium longum subsp. infantis has dual antimicrobial and immunomodulatory activity

Bacteriocins are ribosomally-synthesized antimicrobial peptides produced by bacteria with either narrow or broad spectrum activity. Many genome mining studies have indicated that bacteriocin gene clusters are widespread within certain gut microbiota members. In early life, Bifidobacterium comprise the dominant microbiota genus in vaginally delivered and breast-fed infants, with high levels associated with improved health. However, in many cases the mechanisms underlying these beneficial effects are unknown, although a limited number of studies have suggested that bacteriocin production by Bifidobacterium may represent a key mechanism for preventing pathogen over-growth. Here, we used BAGEL4 and antiSMASH to identify putative bacteriocin sequences in the whole genome sequences of 33 Bifidobacterium strains isolated from infants participating in two clinical studies. We identified a novel non-lantibiotic bacteriocin from Bifidobacterium longum subsp. infantis LH\_664, with 40% sequence homology to Lactococcin 972 from Lactococcus lactis subsp. lactis . The putative bacteriocin (Bifidococcin\_664) was chemically synthesized and studied for antimicrobial and immune-modulatory activities. We determined it has discrete activity against Clostridium perfringens and it appears to have novel immune stimulatory activities, promoting macrophage phagocytosis and specific cytokine release. These data highlight strain-specific beneficial properties in the early life genus Bifidobacterium , and suggest avenues for development of novel and highly specific dual action antimicrobials, and possible probiotic strains, that are active against clinically important bacterial pathogens. Data summary Samples LH\_9 to LH\_666 were previously sequenced and deposited to ENA under accession numbers ERS2658025-ERS2658043. Samples LH\_986 to LH\_1052 are newly sequenced and deposited to NCBI under accession numbers SAMN24838598-SAMN24838611. Additionally, previously assembled publicly available sequences (n=7) were retrieved online from NCBI Genomes database. See Supplementary Table S1 for further details. ### Competing Interest Statement The authors have declared no competing interest.