Isolation and characterization of a novel gamma-radiation-resistant bacterium from hot spring in Iran.

30 pure colonies with various colors and shapes were isolated from the samples of water and mud which were collected from the Abe-Siah hot springs in Ramsar, a city in north of Iran, with high-level of radiation (up to 4 Gy). Colonies were irradiated by 22 KGy radiations and only one of them survived. The survived bacterium with an optimum growth of 30 to 37 degrees C, pH 6 to 7, and at minimum of 5% NaCl concentration showed promising characteristics. This strain is aerobic, mesophilic, white colony, with catalase-positive, oxidase-negative, non motile, spore forming, rod-shape and finally Gram positive. Strain Bacillus sp. WHO represented a strain of genus Bacillus megaterium according to a phylogenetic analysis of the 16S rDNA and biochemical features. Its radio-resistancy was compared with E. coli and B. megaterium which were inactivated in 2 KGy and 5.9 KGy respectively. In order to reveal the mechanisms of this extreme radio-resistancy and WHO DNA repair system we examined its proteomic map, following gamma-irradiation, using two-dimensional polyacrylamide gel electrophoresis and silver-staining. The expression levels of majority number of protein spots showed significant changes under radiation stress.