C# zyxwvutsrqpo A % 'L 3n Arch Microbio1 (1986) 144:163-165 Archives of II 0 Springer-Verlag 1986 I Interspecific hydrogen transfer during methanol degradation by zyxwvut Sporomusa acidovorans and hydrogenophilic anaerobes ..- . Ralf Cord-Ruwisch and Bernard Ollivier Laboratoire de Microbiologie ORSTOM, Université de Provence, 3 Place Victor-Hugo, F-i 3331 Marseille, Cedex 3, France Abstract. In the presence of active hydrogenophilic sulfate- reducing bacteria, the homoacetogenic bacterium zyxwvuts Sporo- musa acidovoraiis did not produce acetate during methanol degradation. HzS and presumably COz were the only end products. Since the sulfate-reducer did not degrade metha- nol or acetate, the sulfidogenesis from methanol was related to a complete interspecific hydrogen transfer between both species. * ' In coculture with hydrogenophilic methanogenic bac- teria (Methanobacteriumformicicum, Metliaiiospirillum hun- gatei), the interspecific hydrogen transfer with S. acidovo- ram was incomplete. Beside CH4 and presumably COz, acetate was produced. The results suggested that Hz-produc- tion and Hz-consumption were involved during anaerobic methanol degradation by S. acidovorans and the hydrogeno- philic anaerobes play an important role during methanol degradation by homoacetogenic bacteria in anoxic environ- ments. Key words: Methanogenesis - Sulfidogenesis - Homoace- togenesis - Competition for Hz - Sporomusa acidovo- rans - Interspecies hydrogen transfer ~~ Methanol is formed in nature during the anaerobic degrada- tion of pectin, a major component of plant cell walls (Schink and Zeikus 1981). In anoxic environments, methanol is a typical methanogenic substrate (Oremland et al. 1982). Therefore anaerobic enrichments in the absence of sulfate lead generally to the development of methylotrophic methanogenic bacteria (König and Stetter 1982; Miller and Wolin 1983; Sharak-Genthner et al. 1981). However in anaerobic upflow reactors fed with methanolic wastes, methanol was partially degraded to ace- tate (Lettinga et al. 1979, 1981). A sporulating homo- acetogen has been shown to be responsible for that reaction (Adamse and Vezeboer 1982). Anaerobic CH4 producing enrichment cultures on meth- anol from a fermenter fed with alcohol distillation wastes contained Sporomusa acidovorans, an homoacetogen as pre- dominant methanol-degrader (Ollivier et al. 1985).Attempts to isolate methylotrophic methanogens failed. Therefore, methanogenesis was thought to result from the degradation of acetate, the only endproduct excreted by S. acidovorans. But aceticlastic methanogens (Metliaiiothrix sp. and Offprint requests to: R. Cord-Ruwisch Methanosarciiia sp.) which differ morphologically from all other methanogens were never observed. The predominant methanogenic bacterium in this environment was a rod shaped bacterium, morphologically related to hydrogeno- philic Methanobacterium species. These observations indicated that Hz rather than acetate was the intermediary product during methanogenesis from methanol. Materials and methods Sources of organisms Methanospirillum hungatei (DSM 864) and Desulfovibrio vul- garis G6 were isolated from the defined synthrophic associa- tion with Syntliroplius bushwellii (DSM 2612TB). Methano- bacterium formicicum strain MF and Methaiiosarciria 227 were kindly provided by Prof. R. S. Wolfe, University of Illinois, USA. Sporomusa acidovorans was from the collec- tion of our laboratory (DSM 3132). Medium and growth conditions The anoxic mineral, bicarbonate buffered, sulfide reduced medium was prepared as described for Desulfotoinaculum sapomandens (Cord-Ruwisch and Garcia 1985) and supple- mented with 0.1% yeast extract (Difco). Stock solutions of methanol were autoclaved separately.Transfers were carried out by sterile syringes. Cliemical determinations Sulfide was determined photometrically as colloidal CuS (Cord-Ruwisch 1985). Methane, volatile fatty acids and alcohols were analyzed as previously described (Garcia et al. 1982). . . Results Pure cultures of the homoacetogenic bacterium Sporomusa acidovoraiis degrade methanol solely to acetate. In order to verify the assumption that S. acidovorans liberates reducing equivalents in the form of hydrogen, during methanol degra- dation, the strain was grown in coculture with the hydrogen consuming D. vulgaris strain G6 which degraded neither methanol nor acetate. HzS and presumably COz were the only end products of this methanol degrading coculture (Table 1). The degradation of methanol by the coculture was Cote : p J5.4