Penicillium molds impact the transcriptome and evolution of the cheese bacterium Staphylococcus equorum .

The observation that molds can inhibit the growth of was a catalyst for the antibiotic revolution. Considerable attention has been paid to purified metabolites that inhibit bacteria, but little is known about how species impact the ecology and evolution of bacteria in multispecies microbial communities. Here, we investigated how four different species of can impact global transcription and evolution of a widespread species () using the cheese rind model microbiome. Through RNA sequencing, we identified a core transcriptional response of against all five tested strains, including upregulation of thiamine biosynthesis, fatty acid degradation, and amino acid metabolism as well as downregulation of genes involved in the transport of siderophores. In a 12-week evolution experiment where we co-cultured with the same strains, we observed surprisingly few non-synonymous mutations across populations evolved with the species. A mutation in a putative DHH family phosphoesterase gene only occurred in populations evolved without and decreased the fitness of when co-cultured with an antagonistic strain. Our results highlight the potential for conserved mechanisms of interactions and demonstrate how fungal biotic environments may constrain the evolution of bacterial species.IMPORTANCEFungi and bacteria are commonly found co-occurring both in natural and synthetic microbiomes, but our understanding of fungal-bacterial interactions is limited to a handful of species. Conserved mechanisms of interactions and evolutionary consequences of fungal-bacterial interactions are largely unknown. Our RNA sequencing and experimental evolution data with species and the bacterium demonstrate that divergent fungal species can elicit conserved transcriptional and genomic responses in co-occurring bacteria. molds are integral to the discovery of novel antibiotics and production of certain foods. By understanding how species affect bacteria, our work can further efforts to design and manage -dominated microbial communities in industry and food production.