Phenotypic and genotypic characterization of esterase-producing Ureibacillus thermosphaericus isolated from an aerobic digestor of swine waste

Eight closely related thermophilic strains were isolated from an aerobic an d thermophilic treatment of swine wastes. The pleomorphic cells (short and long rods; cocci) showed peritrichous flagella, terminally swollen sporangi um, and liberated spores exhibiting hairy appendages. The Gram reaction was negative for both young (4 h) and old (48 h) cultures. Several features, s uch as colonial morphology, growth between 35 degreesC and 65 degreesC, pre sence of catalase, presence of spores, and strictly aerobic metabolism (exc ept for one strain), are similar to those found for the genus Bacillus. The inability of the strains to use sugars, except esculin, as source of carbo n and energy and the whole cell fatty acid composition are similar to those found in Bacillus thermosphaericus DSM 10633. Sequence analysis of the 16S rRNA gene revealed 99.8%-99.9% identity for seven of the thermophilic stra ins with this species. A new genus, Ureibacillus, was recently proposed for type strain B. thermosphaericus DSM 10633 The last strain exhibits 97.8% a nd 97.3% identity with Ureibacillus terrenus DSM12654 and Bacillus sp. TP-8 4, respectively. Esterase activities were detected for all strains, and ass ays on p-nitrophenyl butyrate and p-nitrophenyl caprylate revealed that str ains were more active on the shorter substrate.