Bacterial hitchhikers derive benefits from fungal housing

Fungi and bacteria are ubiquitous constituents of all microbiomes, yet mechanisms of microbial persistence in polymicrobial communities remain obscure. Here, we examined the hypothesis that specialized fungal survival structures, chlamydospores, induced by bacterial lipopeptides serve as bacterial reservoirs. We find that symbiotic and pathogenic gram-negative bacteria from non-endosymbiotic taxa enter and propagate in chlamydospores. Internalized bacteria have higher fitness than planktonic bacteria when challenged with abiotic stress. Further, tri-cultures of Ralstonia solanacearum, Pseudomonas aeruginosa, and Aspergillus flavus reveal the unprecedented finding that chlamydospores are colonized by endofungal bacterial communities. Our work identifies a previously unknown ecological role of chlamydospores, provides an expanded view of microbial niches, and presents significant implications for the persistence of pathogenic and beneficial bacteria. [Display omitted] •Bacteria produce lipopeptides that can induce formation of fungal chlamydospores•Gram negative bacteria increase in population sizes in fungal chlamydospores•Internalization increases bacterial fitness when challenged with abiotic stresses•Chlamydospores can harbor more than one bacterial species Venkatesh et al. show that phylogenetically and ecologically diverse free-living bacteria are able to colonize fungal chlamydospores induced by bacterial lipopeptides. Bacterial hitchhikers are able to ingress chlamydospores induced by other bacterial species, and colonization provides the bacteria with survival advantages under abiotic stress.