Abstract
A radiation resistant and thermophilic bacterium strain R4-33 was isolated from radon hot spring water samples,pretreated with 60Co γ-rays and UV irradiation.Tests on morphological,physiological and biochemical characters,fatty acid compositions,(G + C) mol% contents,and 16S rDNA sequencing were conducted.The results showed that strain R4-33 was of rod-shape,Gram-negative,atrichous,and endospore-forming.The optimum growth temperature and pH were 60℃ and 7.5,respectively.The strain utilized glucose,maltose and trehalose as carbon sources,and hydrolyzed casein and starch.Its catalase positive.The strain was sensitive to penicillin,neomycin,erythromycin,vancomycin,streptomycin,gentamycin,amikacin and ampicillin.The major cellular fatty acids were C14:1(48.4%) and C15:1(15.2%).The(G + C) mol% content of DNA was 58.2%.Phylogenetic tree based on 16S rDNA sequence showed R4-33 shared highly similarity to those of species in genus Anoxybacillus,especially to that of Anoxybacillus gonensis(99.5%).Based on the above,the strain R4-33 was proposed to the evolution branch of Anoxybacillus and designated as Anoxybacillu sp.R4-33.The UV and γ-radiation tests showed that the strain R4-33 had an ability of resistance to UV of 396J /m2 and60 Co γ-rays irradiation of 14.0kGy,indicating that the strain was a radiation resistant and thermophilic bacterium.
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