Clostridium caldaquaticum sp. nov., a thermophilic bacterium isolated from a hot spring sediment

A novel anaerobic bacterium, designated SYSU GA19001^T, was isolated from a hot spring sediment sample. Phylogenetic analysis indicated that the isolate belongs to the genus Clostridium, and showed the highest sequence similarity to Clostridium swellfunianum CICC 10730^T (96.63 %) and Clostridium prolinivorans PYR-10^T (96.11 %). Cells of strain SYSU GA19001^T were Gram-stain-positive, spore-forming, rod-shaped (0.6-0.8×2.6-4.0 µm) and motile. Growth was observed at pH 5.0-9.0 (optimum, pH 7.0), 37-55 °C (optimum, 45 °C) and in NaCl concentrations of 0-2.0 % (optimum, 0 %). The genomic DNA G+C content was 31.62 %. The major cellular fatty acids of strain SYSU GA19001^T were C_{14 : 0}, iso-C_{15 : 0}, C_{16 : 0} and summed feature 8. The prominent polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol. Meso-diaminopimelic acid was the diamino acid in peptidoglycan. Based on the results of phylogenetic, chemotaxonomic and phenotypic analyses, strain SYSU GA19001^T represents a novel species of the genus Clostridium, for which the name Clostridium caldaquaticum sp. nov. is proposed. The type strain of the proposed novel species is SYSU GA19001^T (=NBRC 115040^T= CGMCC 1.17864^T).