Growth with hydrogen,and further physiological characteristics of Desulfotomaculum species

Growth of Desulfotomaculum orientis, D. ruminis, D. nigrificans and the Desulfotomaculum strains TEP, TWC and TWP, that were newly isolated with sulfate and fatty acids, was studied using defined mineral media. Four of these strains grew with hydrogen plus sulfate as the only energy source. Under these conditions the growth yield of D. orientis in batch culture was 7.5 g cell dry mass per mol sulfate reduced. Growth on methanol with growth yields of about 6 g cell dry mass per mol sulfate was obtained with D. orientis and strain TEP. All strains tested grew slowly with formate as electron donor. Fatty acids from propionate to palmitate were utilized by the strains TEP, TWC and TWP. D. orientis and the strains TEP and TWC were able to utilize the methoxyl groups of trimethoxybenzoate for growth. D. orientis was found to grow chemoautotrophically with hydrogen, carbon dioxide and sulfate; during growth with C₁-compounds no additional organic carbon source was required. Furthermore, D. orientis was able to grow slowly in sulfate-free medium with formate, methanol, ethanol lactate, pyruvate or trimethoxybenzoate. Under these conditions acetate was excreted, indicating the function of carbon dioxide as electron acceptor in a homoacetogenic process. A growth-promoting effect of pyrophosphate added to the medium of Desulfotomaculum species was not observed. The results show a high catabolic and anabolic versatility among Desulfotomaculum species, and indicate that electron transport to sulfate can be the sole energy conserving process in this genus.