Radiation-Tolerant Bacteria Isolated from High Altitude Soil in Tibet.

This study reports the identification of ionising radiation tolerant bacteria from a high elevation arid region of central Tibet. Nineteen isolates were isolated from soil exposed to ionising radiation at doses from 0 to 15 kGy. Isolates were phylogenetically characterised using 16S rRNA gene sequences. Most isolates comprised taxa from the Actinobacteria, Cyanobacteria, Firmicutes and proteobacteria and these survived doses up to 5 kGy. The Firmicutes and Deinococci also survived doses up to 10 kGy, and the highest dose of 15 kGy was survived only by the Deinococci. No altitude-related pattern was discernible within the range 4638-5240 m, instead culturable bacterial estimates for irradiated soil were strongly influenced by the abundance of Deinococci. We conclude that the relatively high UV exposure in Tibet has contributed to the high diversity of radiation tolerant soil bacteria. In addition, the strong association between desiccation-tolerance and radiation tolerance pathways suggests the arid environment may also have selected in favour of radiation tolerant taxa.