New motile anaerobic bacteria growing by succinate decarboxylation to propionate

Abstract

Three strains of new anaerobic, gram-negative bacteria which grew with succinate as sole source of carbon and energy were isolated from anoxic marine and freshwater mud samples. Cells of the three strains were small, non-spore-forming, motile rods or spirilla. The guanine-plus-cytosine content of the DNA of strain US2 was 52.6 + 1.0 tool%, of strain Ft2 63.5 _+ 1.4 tool%, and of strain Ftl 62.6 + 1.0 tool%. Succinate was fermented stoichiometrically to propionate and carbon dioxide. The growth yields were 1.2- 2.6 g dry cell mass per tool succinate degraded. Strains US2 and Ft2 required 0.05% w/v yeast extract in addition to succinate for reproducible growth. Optimal growth occurred at 30~176 and pH 6.8-8.0. Addition of acetate as cosubstrate did not stimulate growth with any strain. Strain Ft2 grew only under strictly anaerobic conditions, whereas strains US2 and Ftl tolerated oxygen up to 20% in the headspace. Strains US2 and Ft2 grew only with succinate. Strain Ftl also converted fumarate, aspartate, and sugars to propionate and acetate. This strain also oxidized propionate with nitrate to acetate. Very low amounts of a c-type cytochrome were detected in propionate plus nitrate- or glucose-grown cells of this strain (0.4 gg x g protein- 1). Moderate activities of avidin-sensitive methylmalonyl-CoA decarboxylase were found in cellfree extracts of all strains.