title: Identification of a reductive tetrachloroethene dehalogenase in Shewanella sediminis.
abstract: The genome sequence of psychrophilic Shewanella sediminis revealed the presence of five putative reductive dehalogenases (Rdhs). We found that cell extracts of pyruvate/fumarate-grown S. sediminis cells catalysed reduced methyl viologen-dependent reductive dechlorination of tetrachloroethene (PCE) to trichloroethene (TCE) at a specific activity of approximately 1 nmol TCE min(-1) (mg protein)(-1). Dechlorination of PCE followed Michaelis-Menten kinetics with an apparent Km of 120 μM PCE. No PCE dechlorination was observed with heat-denatured extract or when cyanocobalamin was omitted from the growth medium; however, the presence of PCE in the growth medium increased PCE transformation rates. Analysis of mutants carrying in-frame deletions of all five Rdhs encoding genes showed that only deletion of Ssed_3769 resulted in the loss of PCE dechlorination activity suggesting that Ssed_3769 is a functional Rdh. This is the first study to show reductive dechlorination activity of PCE in a sediment-dwelling Shewanella species that may be important for linking the flux of organohalogens to organic carbon via reductive dehalogenation in marine sediments.
authors.affiliation: Civil and Environmental Engineering, Stanford University, Stanford, CA 94305, USA.
authors.forename: Svenja T
authors.initials: ST
authors.lastname: Lohner
authors.forename: Alfred M
authors.initials: AM
authors.lastname: Spormann
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D003470:Culture Media / Q000378:metabolism; D004980:Ethane / Q000031:analogs & derivatives / Q000378:metabolism; D019143:Evolution, Molecular; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D054879:Halogenation; D006843:Hydrocarbons, Chlorinated / Q000378:metabolism; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D010269:Paraquat / Q000378:metabolism; D010802:Phylogeny; D016415:Sequence Alignment; D020592:Shewanella / Q000201:enzymology* / Q000235:genetics; D013045:Species Specificity; D014241:Trichloroethylene / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D006843:Hydrocarbons, Chlorinated; D014241:Trichloroethylene; C016134:tetrachloroethane; D010088:Oxidoreductases; C112990:tetrachloroethene dehalogenase; D004980:Ethane; D010269:Paraquat