Deinococcus radiodurans is best known for its extraordinary radiation resistance. Manganese(II) ions can protect proteins from being damaged by super radicals, which is supposed to be the main mechanism through which D. radiodurans has the strong radiation resistance. But the detailed molecular and physiological processes about how Mn(II) ions are transported in this bacterium is still not clear. In this paper, two Mn(II) ions transporter gene (DR1709 and DR2523) mutants were used to study the Mn(II) ions transporting mechanism. Results showed that M1709 was much more sensitive to low concentration of Mn(II) ions than M2523. But it was less sensitive to low concentration of Fe(II) ions than M2523. When there were enough Mn(II) ions in the medium, other genes were also activated to uptake them. But when Mn(II) ions was deficient, DR1709 became the only candidate responsible for Mn(II) assimilation. DR1709 was in charge of Mn(II) ions absorbing, no matter wheather Mn(II) ions supply was enough or not. DR1709 can also control the protease production or secretion to prevent over production. The functions of protease secreted by the strains was limited in radiation resistance. DR2523 was responsible for Mn(II) ions efflux, while DR1709 was a Mn(II) influx transporter, which cannot transport Fe(II) ions.
Key words: Deinococcus radiodurans, radiation resistance, Mn(II) ion transporter, DR1709, DR2523.
DMM, Defined minimal medium; TGY, tryptone-glucose-yeast;ICP-MS, inductive coupled plasma mass spectrometry; PBS, phosphate buffered saline; EDTA, ethylenediaminetetraacetic acid; TEM, transmission electron microscopy; ROS, reactive oxygen species.
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