Isolation and molecular identification of gamma-radiation resistant-bacteria from soil samples of a radioactive site in South Khorasan province

Background and objectives: Radiation resistance has been found widely among bacteria but little is known about the biodiversity of radiation resistant-bacteria in naturally radioactive-contaminated places in Iran. The aim of this study is to identify the radio resistant-bacteria isolated from soil samples in such locations. Materials and Methods: Samples were collected from suspected above sites and cultured on TGY agar and incubated at 300C using serial dilutions. All isolates were treated with gamma-radiation from 0 to 30 kGy doses and then plated on TGY agar medium. A radio-resistant isolate was identified by microbiological methods and verified by 16S rRNA sequencing. Results: From a total of 20 isolates which were recovered from soil samples, one isolate (F1 5kGy) could survive against gamma radiation. Phylogenetic analysis based on 16S rRNA sequencing reconfirmed the conventional identification tests showing that F1 5kG bacterium belonged to Kocuria genus with up to 5000Gy resistance to gamma radiation. Conclusion:The results showed F1 5kG bacterium would be well suited for long-term survival in naturally radioactive-contaminated sites and a suitable candidate for bioremediation of radioactive waste. Moreover, identification of proteins which involved in radio resistancy could add further application of this strain in future studies.