Radiation Response of Potassium Efflux in Micrococcus radiodurans and Sarcina lutea

The loss of potassium from irradiated organisms, including yeast (1-3) and bacteria (4), has been shown to be dose-dependent. Harrison et al. (4) found that both potassium efflux and survival are more radioresistant in Escherichia coli strain B/r than in strain B. Recent studies of the highly radioresistant tetrad bacterium Micrococcus radiodurans (5, 6) have demonstrated a bound radioprotective agent, probably of a sulfhydryl nature, not present in the related relatively sensitive octad bacterium Sarcina lutea. The present study was undertaken to determine if factors contributing to the radioresistance of survival of M. radiodurans also influence the response at the cell surface, with potassium efflux as the criterion of damage. The evidence shows that M. radiodurans is far more resistant to radiation damage at the cell surface than is S. lutea.