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Keywords:

  • Cyanobacterium;
  • N2-fixation;
  • Cs+-resistance;
  • Cs+/Rb+ requirement;
  • osmotolerance

SUMMARY

Spontaneous mutation of the cyanobacterium Nostoc muscorum to a caesium resistant (Cs+-R) phenotype resulted in severe impairment of its nitrogenase activity, oxygenic photosynthesis, chlorophyll a content and osmotolerance. Among alkali cations only Cs+ or Rb+ restored these physiological processes to an almost normal level. Parent and mutant were similar with respect to Cs+ or Rb+ uptake and accumulation and also to regulation by NH4+. The ions Na+ or K+, at much higher concentration, significantly influenced Cs+ uptake and accumulation in both the mutant and the parent. These findings have important implications for cyanobacteria growing in Cs+-polluted habitats.