O-antigen biosynthesis mediates evolutionary trade-offs within a simple community

Abstract

AbstractDiverse populations of bacteriophages infect and co-evolve with their bacterial hosts. Although host recognition and infection occurs within microbiomes, the molecular mechanisms underlying host-phage interactions within a community context remain poorly studied. The biofilms (rinds) of aged cheeses contain taxonomically diverse microbial communities that follow reproducible growth patterns and can be manipulated under laboratory conditions. In this study, we use cheese as a model for studying phage-microbe interactions by identifying and characterising a tractable host-phage pair co-occurring within a model Brie community. We isolated novel bacteriophage TS33 that killsHafniasp. JB232 (hereafterHafnia), a member of the model community. TS33 is easily propagated in the lab and naturally co-occurs in the cheese with the Brie community, rendering it a prime candidate for the study of host-phage interactions. We performed growth assays of theHafnia, TS33 and the fungal community members,Geotrichum candidumandPenicillium camemberti. Employing Random Barcode Transposon Sequencing (RB-TnSeq) experiments, we identified candidate host factors that contribute to TS33 infectivity, many of which are critical to the integrity of bacterial O-antigen. Notably, disruption of these genes results in decreased susceptibility to infection by phage TS33, while simultaneously exhibiting a significant negative effect on the fitness ofHafniain the presence of the fungi. Therefore, O-antigen mutations may have pleiotropic effects on the interactions betweenHafniaand the rest of the Brie community. Ongoing and future studies aim to unearth the molecular mechanisms by which the O-antigen ofHafniamediates its interactions with its viral and fungal partners.