title: Underlying mechanisms for syntrophic metabolism of essential enzyme cofactors in microbial communities.
abstract: Many microorganisms are unable to synthesize essential B vitamin-related enzyme cofactors de novo. The underlying mechanisms by which such microbes survive in multi-species communities are largely unknown. We previously reported the near-complete genome sequence of two ~18-member unicyanobacterial microbial consortia that maintain stable membership on defined medium lacking vitamins. Here we have used genome analysis and growth studies on isolates derived from the consortia to reconstruct pathways for biogenesis of eight essential cofactors and predict cofactor usage and precursor exchange in these communities. Our analyses revealed that all but the two Halomonas and cyanobacterial community members were auxotrophic for at least one cofactor. We also observed a mosaic distribution of salvage routes for a variety of cofactor precursors, including those produced by photolysis. Potentially bidirectional transporters were observed to be preferentially in prototrophs, suggesting a mechanism for controlled precursor release. Furthermore, we found that Halomonas sp. do not require cobalamin nor control its synthesis, supporting the hypothesis that they overproduce and export vitamins. Collectively, these observations suggest that the consortia rely on syntrophic metabolism of cofactors as a survival strategy for optimization of metabolic exchange within a shared pool of micronutrients.
authors.affiliation: Pacific Northwest National Laboratory, Richland, WA, USA.
authors.forename: Margaret F
authors.initials: MF
authors.lastname: Romine
authors.affiliation: Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA.|A.A. Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, Russia.
authors.forename: Dmitry A
authors.initials: DA
authors.lastname: Rodionov
authors.affiliation: Pacific Northwest National Laboratory, Richland, WA, USA.
authors.forename: Yukari
authors.initials: Y
authors.lastname: Maezato
authors.affiliation: Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA.
authors.forename: Andrei L
authors.initials: AL
authors.lastname: Osterman
authors.affiliation: Pacific Northwest National Laboratory, Richland, WA, USA.
authors.forename: William C
authors.initials: WC
authors.lastname: Nelson
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000378:metabolism*; D003067:Coenzymes / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D059013:Microbial Consortia; D014803:Vitamin B Complex / Q000378:metabolism*
chemical_list: D003067:Coenzymes; D026901:Membrane Transport Proteins; D014803:Vitamin B Complex