CHARACTERIZATION OF DESULFITOBACTERIUM-CHLORORESPIRANS SP-NOV, WHICH GROWS BY COUPLING THE OXIDATION OF LACTATE TO THE REDUCTIVE DECHLORINATION OF 3-CHLORO-4-HYDROXYBENZOATE

Strain Co23, an anaerobic spore-forming microorganism, was enriched an d isolated from a compost soil on the basis of its ability to grow wit h 2,3-dichlorophenol (DCP) as its electron acceptor. ortho chlorines w ere removed from polysubstituted phenols but not from monohalophenols. Growth by chlororespiration was indicated by a grow th yield of 3.24 g of cells per mol of reducing equivalents (as 2[H]) from lactate oxid ation to acetate in the presence of 3-chloro-4-hydroxybenzoate but no growth in the absence of the halogenated electron acceptor. Other indi cators of chlororespiration were the fraction of electrons from the el ectron donor used for dechlorination (0.67) and the H-2 threshold conc entration of <1.0 ppm. Additional electron donors utilized for reducti ve dehalogenation were pyruvate, formate, butyrate, crotonate, and H-2 . Pyruvate supported homoacetogenic growth in the absence of an electr on acceptor, Strain Co23 also used sulfite, thiosulfate, and sulfur as electron accepters for growth, but it did not use sulfate, nitrate or fumarate. The temperature optimum for growth was 37 degrees C; howeve r, the rates of dechlorination were optimum at 45 degrees C and activi ty persisted to temperatures as high as 55 degrees C, The 16S rRNA seq uence was determined, and strain Co23 was found to be related to Desul fitobacterium dehalogenans JW/IU DC1 and Desulfitobacterium strain PCE 1, with sequence similarities of 97.2 and 96.8%, respectively. The phy logenetic and physiological properties exhibited by strain Co23 place it into a new species designated Desulfitobacterium chlororespirans.