Identification of a reductive tetrachloroethene dehalogenase in Shewanella sediminis

• Published in: Philosophical transactions of the Royal Society of London. Series B. Biological sciences 2013-04, Vol.368 (1616), p.20120326-20120326
• Main Authors: Lohner, Svenja T., Spormann, Alfred M.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Bacterial Proteins - genetics; Bacterial Proteins - isolation & purification; Bacterial Proteins - metabolism; Culture Media - metabolism; Ethane - analogs & derivatives; Ethane - metabolism; Evolution, Molecular; Gene Expression Regulation, Bacterial; Genes, Bacterial; Halogenation; Hydrocarbons, Chlorinated - metabolism; Marine Sediment; Molecular Sequence Data; Oxidoreductases - genetics; Oxidoreductases - isolation & purification; Oxidoreductases - metabolism; Paraquat - metabolism; Phylogeny; Reductive Dehalogenase; Sequence Alignment; Shewanella; Shewanella - enzymology; Shewanella - genetics; Species Specificity; Tetrachloroethene; Trichloroethene; Trichloroethylene - metabolism
• ISSN: 0962-8436; 1471-2970
• DOI: 10.1098/rstb.2012.0326

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.