Isolation, Properties and Kinetics of Growth of a Thermophilic Bacillus

A strictly aerobic, thermophilic, spore-forming bacteria was isolated from a soil sample collected in Campos dos Goytacazes City, Rio de Janeiro, Brazil. The cells of this organism were Gram-positive, catalase positive, actively motile, 1.2 μm wide and 5.3 μm long. Growth occurred at pH values ranging from 6.5 to 9.0, and optimum growth occurred at about pH 7.0. The optimum temperature for growth was around 55oC, and the upper temperature limit for growth was around 70oC. Yeast extract stimulated growth on glucose and was obligately required at supraoptimal temperatures (65oC). The results of 16S rRNA sequence comparisons indicated that the isolate was closely related to Bacillus caldoxylolyticus and Bacillus sp strain AK1, and these three organisms exhibited levels of ribossomal DNA sequence homology of 94%.