title: Ecological implications of hypoxia-triggered shifts in secondary metabolism.
abstract: Members of the actinomycete genus Streptomyces are non-motile, filamentous bacteria that are well-known for the production of biomedically relevant secondary metabolites. While considered obligate aerobes, little is known about how these bacteria respond to periods of reduced oxygen availability in their natural habitats, which include soils and ocean sediments. Here, we provide evidence that the marine streptomycete strain CNQ-525 can reduce MnO2via a diffusible mechanism. We investigated the effects of hypoxia on secondary metabolite production and observed a shift away from the antibiotic napyradiomycin towards 8-amino-flaviolin, an intermediate in the napyradiomycin biosynthetic pathway. We purified 8-amino-flaviolin and demonstrated that it is reversibly redox-active (midpoint potential -474.5 mV), indicating that it has the potential to function as an endogenous extracellular electron shuttle. This study provides evidence that environmentally triggered changes in secondary metabolite production may provide clues to the ecological functions of specific compounds, and that Gram-positive bacteria considered to be obligate aerobes may play previously unrecognized roles in biogeochemical cycling through mechanisms that include extracellular electron shuttling.
authors.affiliation: Scripps Institution of Oceanography, Center for Marine Biotechnology and Biomedicine, University of California San Diego, La Jolla, CA, USA.
authors.forename: Kelley A
authors.initials: KA
authors.lastname: Gallagher
authors.affiliation: Department of Earth Sciences, University of Southern California, Los Angeles, CA, USA.
authors.forename: Greg
authors.initials: G
authors.lastname: Wanger
authors.affiliation: Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, USA.
authors.forename: Jane
authors.initials: J
authors.lastname: Henderson
authors.affiliation: Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Llorente
authors.affiliation: Scripps Institution of Oceanography, Center for Marine Biotechnology and Biomedicine, University of California San Diego, La Jolla, CA, USA.
authors.forename: Chambers C
authors.initials: CC
authors.lastname: Hughes
authors.affiliation: Scripps Institution of Oceanography, Center for Marine Biotechnology and Biomedicine, University of California San Diego, La Jolla, CA, USA.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Jensen
mesh_terms: D000693:Anaerobiosis / Q000502:physiology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D053898:Biosynthetic Pathways; D004463:Ecology; D019015:Geologic Sediments / Q000382:microbiology; D017895:Manganese Compounds / Q000378:metabolism*; D009281:Naphthalenes / Q000378:metabolism*; D009285:Naphthoquinones / Q000378:metabolism; D010084:Oxidation-Reduction; D010087:Oxides / Q000378:metabolism*; D010100:Oxygen / Q000032:analysis; D064210:Secondary Metabolism / Q000502:physiology*; D013302:Streptomyces / Q000378:metabolism*
chemical_list: C576768:8-amino-2,5,7-trihydroxynaphthalene-1,4-dione; D000900:Anti-Bacterial Agents; D017895:Manganese Compounds; D009281:Naphthalenes; D009285:Naphthoquinones; D010087:Oxides; C054847:napyradiomycin A1; D010100:Oxygen; C016552:manganese dioxide