Clostridium magnum sp. nov., a non-autotrophic homoacetogenic bacterium

A new mesophilic, sporeforming, strictly anaerboic bacterium was isolated form enrichments with 2,3-butanediol as sole substrate and pasteurized freshwater sediment as inoculum. Cells were large, motile rods, and elliptical spores were formed subterminally or centrally. They stained Gram-negative, but no typical outer membrane layer could be observed by electron microscopy of ultrathin sections. 2,3-Butanediol, acetoin, fructose, glucose, sucrose, xylose, malate and citrate served as substrates and were completely converted to acetate with concomitant reduction of carbon dioxide. Growth on glucose (=1.4 h) was faster than on butanediol (=3.6 h). No growth occurred on hydrogen/carbon dioxide, on formate or on methanol. The guanine plus cytosine content of the DNA was 29.1%. The new isolate is described as a new species, sp. nov.