Isolation and characterization of a novel γ‐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 °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 γ‐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. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)