Influence of different electron donors and accepters on dehalorespiration of tetrachloroethene by Desulfitobacterium frappieri TCE1

Strain TCE1, a strictly anaerobic bacterium that can grow by reductive dech lorination of tetrachloroethene (PCE) and trichloroethene (TCE), was isolat ed by selective enrichment from a PCE-dechlorinating chemostat mixed cultur e, Strain TCE1 is a gram-positive, motile, curved rod-shaped organism that is 2 to 4 by 0.6 to 0.8 mu m and has approximately six lateral flagella. Th e pH and temperature optima for growth are 7.2 and 35 degrees C, respective ly. On the basis of a comparative 16S rRNA sequence analysis, this bacteriu m was identified as a new strain of Desulfitobacterium frappieri, because i t exhibited 99.7% relatedness to the D. frappieri type strain, strain PCP-1 . Growth with H-2, formate, L-lactate, butyrate, crotonate, or ethanol as t he electron donor depends on the availability of an external electron accep tor. Pyruvate and serine can also be used fermentatively. Electron donors ( except formate and H-2) are oxidized to acetate and CO2. When L-lactate is the growth substrate, strain TCE1 can use the following electron accepters: PCE and TCE (to produce cis-1,2-dichloroethene), sulfite and thiosulfate ( to produce sulfide), nitrate (to produce nitrite), and fumarate (to produce succinate), Strain TCE1 is not able to reductively dechlorinate 3-chloro-1 -hydroxyphenylacetate. The growth yields of the newly isolated bacterium wh en PCE is the electron acceptor are similar to those obtained for other deh alorespiring anaerobes (e.g., Desulfitobacterium sp. strain PCE1 and Desulf itobacterium hafniense) and the maximum specific reductive dechlorination r ates are 4 to 16 times higher (up to 1.4 mu mol of chloride released min(-1 ) . mg of protein(-1)). Dechlorination of PCE and TCE is an inducible proce ss. In PCE-limited chemostat cultures of strain TCE1, dechlorination is str ongly inhibited by sulfite but not by other alternative electron accepters, such as fumarate or nitrate.