The in vivo association of manganese with the chromosome of Micrococcus radiodurans

Extremely high levels of paramagnetic manganese (Mn2+) which quench phosphorescent reactions have been found to inhibit the formation of thymine-containing dimers in M. radiodurans. Lowering the concentration of Mn2+ in the culture medium resulted in a lower intracellular concentration of Mn2+, an increase in the UV-sensitivity of this bacterium, and a larger photochemical yield of thymine-containing dimers. High levels of paramagnetic Mn2+ were not found in other test organisms which are more sensitive to UV-irradiation. One interpretation of this data is that in Micrococcus radiodurans Mn2++ may bind to the chromosome and thereby reduce the photochemical yield of thymine-containing dimers. (author)