ISOLATION AND CHARACTERIZATION OF A MODERATELY THERMOPHILIC ANAEROBICALKALIPHILE, CLOSTRIDIUM-PARADOXUM SP-NOV

Alkaliphilic, moderately thermophilic anaerobic bacteria able to grow above pH 10.5 and 55-degrees-C were isolated from various sewage plant s in the United States. The strains were motile with two to six peritr ichous flagella and formed round to slightly oval terminal spores in t erminally distended and slightly enlarged cells. Sporulated cells rema ined motile. The pH range for growth was between 7.0 and 11.1, with an optimum of around 10.1. At pH 10.1 the temperature range for growth w as between 30 and 63-degrees-C, with an optimum of 56-degrees-C. The s hortest observed doubling time (glucose) was around 16 min at 56-degre es-C and pH 10.1. No dissimilatory sulfate reduction was detected. The organism utilized glucose, fructose, sucrose, maltose, and pyruvate b ut required yeast extract or tryptone for growth. Optimal NaCl concent rations for growth were between 50 and 200 mM. The guanine-plus-cytosi ne content was 30.0 +/- 0.10 mol%. On the basis of unique properties a nd 16S rRNA analysis, the strains are placed in a new species, Clostri dium paradoxum, referring to the unusual retainment of motility by spo rulated cells. Strain JW-YL-7 (DSM 7308) is designated as the type str ain.