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When stay-at-home orders were issued to slow the spread of COVID-19, building occupancy (and water demand) was drastically decreased in many buildings. There was concern that widespread low water demand may cause unprecedented

Fungi defend their ecological niche against antagonists by producing antibiosis molecules. Some of these molecules are only produced upon confrontation with the antagonist. The basidiomycete Coprinopsis cinerea induces the expression of the sesquiterpene synthase-encoding gene cop6 and its two neighboring genes coding for cytochrome P450 monooxygenases in response to bacteria. We further investigated this regulation of cop6 and examined if the gene product is involved in the production of antibacterials. Cell-free supernatants of axenic cultures of the Gram-positive bacterium Bacillus subtilis were sufficient to induce cop6 transcription assessed using a fluorescent reporter strain. Use of this strain in a microfluidic device revealed that the cop6 gene was induced in all hyphae directly exposed to the supernatant and that induction occurred within less than one hour. Targeted replacement of the cop6 gene demonstrated the requirement of the encoded synthase for the biosynthesis of the sesquiterpene lagopodin B, a previously reported antibacterial compound from related species. Accordingly, lagopodin B from C. cinerea inhibited the growth of several Gram-positive bacteria including B. subtilis but not Gram-negative bacteria. Our results demonstrate that the C. cinerea vegetative mycelium responds to soluble compounds of a bacterial culture supernatant by local production of an antibacterial secondary metabolite.

Summary Initial enteropathogen growth in the microbiota-colonized gut is poorly understood. Salmonella Typhimurium is metabolically adaptable and can harvest energy by anaerobic respiration using microbiota-derived hydrogen (H2) as an electron donor and fumarate as an electron acceptor. As fumarate is scarce in the gut, the source of this electron acceptor is unclear. Here, transposon sequencing analysis along the colonization trajectory of S. Typhimurium implicates the C4-dicarboxylate antiporter DcuABC in early murine gut colonization. In competitive colonization assays, DcuABC and enzymes that convert the C4-dicarboxylates aspartate and malate into fumarate (AspA, FumABC), are required for fumarate/H2-dependent initial growth. Thus, S. Typhimurium obtains fumarate by DcuABC-mediated import and conversion of L-malate and L-aspartate. Fumarate reduction yields succinate, which is exported by DcuABC in exchange for L-aspartate and L-malate. This cycle allows S. Typhimurium to harvest energy by H2/fumarate respiration in the microbiota-colonized gut. This strategy may also be relevant for commensal E. coli diminishing the S. Typhimurium infection.

Initial enteropathogen growth in the microbiota-colonized gut is poorly understood. Salmonella Typhimurium is metabolically adaptable and can harvest energy by anaerobic respiration using microbiota-derived hydrogen (H

Enteropathogen growth in the microbiota-colonized gut is poorly understood. Salmonella Typhimurium is metabolically plastic and can harvest energy by anaerobic respiration using hydrogen (H2), a product of microbiota metabolism, as an electron donor and fumarate as an electron acceptor. As fumarate is scarce in the gut, the source of this electron acceptor is unclear. Transposon sequencing analysis along the colonization-trajectory of S.Typhimurium implicated the C4-dicarboxylate exchanger DcuABC in murine gut colonization. In competitive colonization assays, DcuABC and enzymes converting the C4-dicarboxylates aspartate and malate into fumarate (AspA, FumABC), were required for fumarate/H2-dependent growth. Thus, S.Typhimurium obtains fumarate by DcuABC-mediated import and the subsequent conversion of L-malate and L-aspartate into fumarate. Fumarate reduction yields succinate, which is exported by DcuABC in exchange for L-aspartate and L-malate. This mechanism allows S.Typhimurium to harvest energy by H2/fumarate respiration in the microbiota-colonized gut. It might be relevant for other enteropathogens encoding the requisite genes.