Abstract: Abstract: A thermophilic strain CW₂ was isolated and purified from the soil around a hot spring in Chang-bai mountains. The cells of isolate CW ₂ stain Gram positively, the morphology of the cells of isolate was c hanged from rod to round in the process of growth, the cells in the initial phase of logarithmic growth were longrod, majority of cells singly existed, minority of cells were geminated or formed a long discontinuous chain, until to invariable phage of growth, the c ells changed to globe. Strain CW₂ formed spore, had capsule, flagella, motility, no parasporal crystal, V.P. test was negative, could catabolism starch, could not catabolism fibrin, aerobic, but could grow without oxygen, grow at and between 30～60 ℃(opt. 55 ℃), grow at and between pH 5~11(opt. pH 7.5). The neonatal colonies were milk-white and round and the margin is regular, growing along with the strain CW₂, the colonies randomly developed to three shapes, finally formed irregular round colonies, flowery colonies or radiate compressed colonies.

Key words: hot spring in Chang-bai mountains, thermophilic bacterium, isolation and purification, character study