Phenotypic and genotypic characterization of esterase-producingUreibacillus thermosphaericusisolated from an aerobic digestor of swine waste

Abstract

Eight closely related thermophilic strains were isolated from an aerobic and thermophilic treatment of swine wastes. The pleomorphic cells (short and long rods; cocci) showed peritrichous flagella, terminally swollen sporangium, and liberated spores exhibiting hairy appendages. The Gram reaction was negative for both young (4 h) and old (48 h) cultures. Several features, such as colonial morphology, growth between 35°C and 65°C, presence of catalase, presence of spores, and strictly aerobic metabolism (except 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 carbon 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 strains with this species. A new genus, Ureibacillus, was recently proposed for type strain B. thermosphaericus DSM 10633 The last strain exhibits 97.8% and 97.3% identity with Ureibacillus terrenus DSM12654 and Bacillus sp. TP-84, respectively. Esterase activities were detected for all strains, and assays on p-nitrophenyl butyrate and p-nitrophenyl caprylate revealed that strains were more active on the shorter substrate.Key words: Ureibacillus thermosphaericus, thermophilic, esterase.