title: Proteomic analysis reveals metabolic and regulatory systems involved in the syntrophic and axenic lifestyle of Syntrophomonas wolfei.
abstract: Microbial syntrophy is a vital metabolic interaction necessary for the complete oxidation of organic biomass to methane in all-anaerobic ecosystems. However, this process is thermodynamically constrained and represents an ecosystem-level metabolic bottleneck. To gain insight into the physiology of this process, a shotgun proteomics approach was used to quantify the protein landscape of the model syntrophic metabolizer, Syntrophomonas wolfei, grown axenically and syntrophically with Methanospirillum hungatei. Remarkably, the abundance of most proteins as represented by normalized spectral abundance factor (NSAF) value changed very little between the pure and coculture growth conditions. Among the most abundant proteins detected were GroEL and GroES chaperonins, a small heat shock protein, and proteins involved in electron transfer, beta-oxidation, and ATP synthesis. Several putative energy conservation enzyme systems that utilize NADH and ferredoxin were present. The abundance of an EtfAB2 and the membrane-bound iron-sulfur oxidoreductase (Swol_0698 gene product) delineated a potential conduit for electron transfer between acyl-CoA dehydrogenases and membrane redox carriers. Proteins detected only when S. wolfei was grown with M. hungatei included a zinc-dependent dehydrogenase with a GroES domain, whose gene is present in genomes in many organisms capable of syntrophy, and transcriptional regulators responsive to environmental stimuli or the physiological status of the cell. The proteomic analysis revealed an emphasis on macromolecular stability and energy metabolism by S. wolfei and presence of regulatory mechanisms responsive to external stimuli and cellular physiological status.
authors.affiliation: Department of Botany and Microbiology, University of Oklahoma Norman, OK, USA.
authors.forename: Jessica R
authors.initials: JR
authors.lastname: Sieber
authors.affiliation: Department of Botany and Microbiology, University of Oklahoma Norman, OK, USA.
authors.forename: Bryan R
authors.initials: BR
authors.lastname: Crable
authors.affiliation: Department of Geological Sciences, University of Michigan Ann Arbor, MI, USA.
authors.forename: Cody S
authors.initials: CS
authors.lastname: Sheik
authors.affiliation: Chemical Sciences Division, Oak Ridge National Laboratory Oak Ridge, TN, USA.
authors.forename: Gregory B
authors.initials: GB
authors.lastname: Hurst
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Lars
authors.initials: L
authors.lastname: Rohlin
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Gunsalus
authors.affiliation: Department of Botany and Microbiology, University of Oklahoma Norman, OK, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: McInerney
keywords: Syntrophomonas wolfei; hydrogen; interspecies electron transfer; methanogenesis; reverse electron transfer; syntrophy