Clostridium pascui sp. nov., a New Glutamate-Fermenting Sporeformer from a Pasture in Pakistan

Four strains of an obligately anaerobic spore-forming bacterium were isolated from soil samples from a donkey pasture in Pakistan. Comparative 16S rRNA sequence analysis demonstrated that the strains are members of phylogenetic cluster I of the genus Clostridium (Collins et al. 1994). The strains are mesophilic, nonsaccharolytic, and nonproteolytic, utilize glutamate and histidine, and produce indole. Acetate, butyrate, ethanol, hydrogen, and carbon dioxide are the products of fermentation. Although the strains phenotypically resemble the classical glutamate-fermenting clostridia, such as Clostridium cochlearium, Clostridium tetanomorphum, Clostridium tetani, and especially Clostridium malenominatum, they differ from these organisms in sugar utilization, cellular fatty acid composition, and cellular protein pattern and by a 16S rRNA sequence divergence value of approximately 4 to 8%. Phylogenetically, the strains are more closely related to Clostridium estertheticum (sequence divergence, approximately 5%) and Clostridium subterminale (sequence divergence, approximately 5%) but are phenotypically readily distinguished from these species. On the basis of phenotypic and genotypic criteria, we conclude that the four strains are members of a new species of the genus Clostridium, for which the name Clostridium pascui is proposed. The type strain is strain Cm19 (= DSM 10365).