title: Reconstruction and regulation of the central catabolic pathway in the thermophilic propionate-oxidizing syntroph Pelotomaculum thermopropionicum.
abstract: Obligate anaerobic bacteria fermenting volatile fatty acids in syntrophic association with methanogenic archaea share the intermediate bottleneck step in organic-matter decomposition. These organisms (called syntrophs) are biologically significant in terms of their growth at the thermodynamic limit and are considered to be the ideal model to address bioenergetic concepts. We conducted genomic and proteomic analyses of the thermophilic propionate-oxidizing syntroph Pelotomaculum thermopropionicum to obtain the genetic basis for its central catabolic pathway. Draft sequencing and subsequent targeted gap closing identified all genes necessary for reconstructing its propionate-oxidizing pathway (i.e., methylmalonyl coenzyme A pathway). Characteristics of this pathway include the following. (i) The initial two steps are linked to later steps via transferases. (ii) Each of the last three steps can be catalyzed by two different types of enzymes. It was also revealed that many genes for the propionate-oxidizing pathway, except for those for propionate coenzyme A transferase and succinate dehydrogenase, were present in an operon-like cluster and accompanied by multiple promoter sequences and a putative gene for a transcriptional regulator. Proteomic analysis showed that enzymes in this pathway were up-regulated when grown on propionate; of these enzymes, regulation of fumarase was the most stringent. We discuss this tendency of expression regulation based on the genetic organization of the open reading frame cluster. Results suggest that fumarase is the central metabolic switch controlling the metabolic flow and energy conservation in this syntroph.
authors.affiliation: Laboratory of Applied Microbiology, Marine Biotechnology Institute, Heita, Kamaishi, Iwate 026-0001, Japan. kazuya.watanabe@mbio.jp
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Kosaka
authors.forename: Taku
authors.initials: T
authors.lastname: Uchiyama
authors.forename: Shun-ichi
authors.initials: S
authors.lastname: Ishii
authors.forename: Miho
authors.initials: M
authors.lastname: Enoki
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Imachi
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Kamagata
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Ohashi
authors.forename: Hideki
authors.initials: H
authors.lastname: Harada
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ikenaga
authors.forename: Kazuya
authors.initials: K
authors.lastname: Watanabe
mesh_terms: D000214:Acyl Coenzyme A / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001673:Biodegradation, Environmental; D015256:Coenzyme A-Transferases / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010459:Peptococcaceae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D011422:Propionates / Q000378:metabolism*; D020543:Proteome; D017422:Sequence Analysis, DNA
chemical_list: D000214:Acyl Coenzyme A; D001426:Bacterial Proteins; D011422:Propionates; D020543:Proteome; C015357:methylmalonyl-coenzyme A; D015256:Coenzyme A-Transferases; C031212:acyl-CoA transferase