High resistance of some oligotrophic bacteria to ionizing radiation

: The resistance against ionizing radiation of seven cultures of oligotrophic and eutrophic bacteria was investigated in the interval 0-360 Gr/h. It is determine that all of tested bacteria are distributed into three groups according to the lever of their resistance. Most resistant were: Methylobacterium organophilum, Pedodermatophilus halotolerans (LD50 = 270 Cr/h). These organisms are close to Deinococcus radiodurans in the survival. Middle resistance shown water-born ring-forming bacteria Flectobacillus major, Arcocella aquatica (LD50 = 173 and 210 Gr/h respectively). High sensitive were eutrophs: Pseudomonas fluorescens, Escherichia coli (LD50 = 43 and 38 Gr/h respectively). By use of X-ray microanalysis was shown that after the radiation potassium content in cell was increased and calcium content was decreased. The elements content in the cells of eutrophs (Escherichia coli) remains without change. In present paper are also discussed possible mechanisms of the resistance of oligotrophs against gamma-irradiation.