Differential response of NaCl-Resistant mutants of the cyanobacterium Nostoc muscorum to salinity and osmotic stresses

In the parent strain of Nostoc muscorum, the percentage survival, nitrogenase activity and oxygenic photosynthesis were severely impaired by NaCl (ionic) and sucrose (non-ionic) stresses. Spontaneously occurring NaCl-Resistant mutant clones of the cyanobacterium N. muscorum were found to exhibit differential responses under ionic and non-ionic stresses. One of the mutants (NaCl-R) was found to show resistance in terms of percentage survival, nitrogenase activity and oxygenic photosynthesis under saline (ionic) as well as osmotic (non-ionic) stresses and showing compatible solute strategy for such adaptation. Another mutant (Na+-R) was found to show resistance only to salinity stress and showed an enhanced Na+-efflux system driven by H+. The Na+-R mutant differed from the NaCl-R mutant strain in the sense that it was sucrose sensitive.