Bacillus flavothermus, a newly isolated facultative thermophile

Abstract

A sample from a hot spring on the northern island of New Zealand contained five different thermophilic bacterial strains. One strain with peculiar properties, i.e. the formation of dark yellow colonies at 30°C as well as at 70°C, was further characterized. It was found to be a gram-positive, facultatively aerobic, motile Bacillus species, with terminal endospores. According to the physiological properties the strain closely resembled B. coagulans. However, two typical characteristics were contradictory to this conclusion, namely the intense yellow pigmentation of the colonies and the range of growth temperature. The latter was found to reach from 30 to 70°C, with an optimum at 60°C under aerobic and at 65°C under anaerobic conditions. Growth at moderate temperatures was slower than at 60°C, but the final cell yields were almost equal. The strain can therefore be considered as facultatively thermophilic. The pigment, which was found to be located in the cytoplasmic membrane, was spectroscopically identified as a carotenoid.

Because the characteristics of this strain did not correspond with any of the Bacillus species described thus far, we concluded, that we had isolated a novel strain, for which the name Bacillus flavothermus is proposed.