A strictly anaerobic, slightly halophilic and moderately thermophilic, sporulating rod designated strain DVird3(T) was isolated from deep-sea hydrothermal vent samples collected at a depth of approximately 800 m on the Atlantic Ocean Ridge. Strain DVird3(T) possessed a few laterally inserted flagella, had a DNA G+C content of 33.1 mol% and grew optimally at pH 6.6 and at 45 degreesC. Growth was observed at temperatures between 20 and 58 degreesC and at pH values between 5.8 and 8.2. The optimum NaCl concentration for growth was 3% sea salt (30 g l(-1)); no growth was observed in the presence of 15 or 60 g sea salt l(-1). Strain DVird3(T) is heterotrophic and utilizes some sugars and various single amino acids. Acetate was the main fatty acid detected from carbohydrate fermentation, together with H-2 and CO2. Gelatin was used as an energy source. It performed the Stickland reaction. Phylogenetically, strain DVird3T branched with members of cluster XI of the order Clostridiales, with Clostridium halophilum as its closest relative (similarity of 94.6%). On the basis of its phenotypic, genotypic and phylogenetic characteristics, strain DVird3(T) (= DSM 15212(T) = CIP 107654(T)) is proposed as the type strain of a novel species of the genus Clostridium, Clostridium caminithermale sp. nov.