Bacterial competition mediated by siderophore production among the human nasal microbiota

Abstract

19Resources available in the human nasal cavity are limited. Therefore, to successfully 20 colonize the nasal cavity, bacteria must compete for scarce nutrients. Competition may 21 occur directly through interference (e.g., antibiotics) or indirectly by nutrient 22 sequestration. To investigate the nature of nasal bacterial competition, we performed 23 co-culture inhibition assays between nasal Actinobacteria and Staphylococcus spp. We 24 found that Staphylococcus epidermidis isolates were sensitive to growth inhibition by 25 Actinobacteria but Staphylococcus aureus isolates were resistant to inhibition. Among 26 Actinobacteria, we observed that Corynebacterium spp. were variable in their ability to 27 inhibit S. epidermidis. We sequenced the genomes of ten Corynebacterium spp. 28 isolates, including three Corynebacterium propinquum that strongly inhibited S. 29 epidermidis and seven other Corynebacterium spp. isolates that only weakly inhibited S. 30 epidermidis. Using a comparative genomics approach, we found that the C. propinquum 31 genomes were enriched in genes for iron acquisition and encoded a biosynthetic gene 32 cluster (BGC) for siderophore production, absent in the non-inhibitory Corynebacterium 33 spp. genomes. Using a chromeazurol S assay, we confirmed that C. propinquum 34 produced siderophores. We demonstrated that iron supplementation rescued S. 35 epidermidis from inhibition by C. propinquum, suggesting that inhibition was due to iron 36 restriction through siderophore production. Using comparative metabolomics, we 37 identified the siderophore produced by C. propinquum as dehydroxynocardamine. 38

Needles in haystacks: reevaluating old paradigms for the discovery of bacterial secondary metabolites

“…106 Other natural products shape competitive landscapes other body sites. [106][107][108][109][110] In a remarkable project at Yale University, Strobel and Bascom-Slack engaged undergraduate students in scientic research through a course that involved a eld trip to the Equadorian rainforest to isolate fungi from plants and screen them for biological activities upon return to the lab. 74 The project explored several novelties-fungi, which have been less well combed than bacteria for natural products; Equador's rainforest, which is inaccessible to most researchers; and endophytes, which reside inside plant stems.…”