Cyanobacterial Mn-catalase 'KatB': Molecular link between salinity and oxidative stress resistance.

Catalases are ubiquitous enzymes that detoxify HO in virtually all organisms exposed to oxygen. The filamentous, nitrogen-fixing cyanobacterium, PCC 7120, shows the presence of 2 genes ( and ) that encode Mn-catalases. We have recently shown that pre-treatment of with NaCl causes substantial induction of the KatB protein, which consequently leads to increased oxidative stress resistance in that cyanobacterium. Interestingly, when compared to the wild-type, the mutant shows decreased growth and impaired photosynthetic activity in the presence of NaCl. Furthermore, the NaCl-treated mutant is extremely sensitive to HO. In this study, the ultrastructural changes occurring in the mutant and the wild-type cells are analyzed to understand the cellular basis of the above-mentioned protective phenomena. Other data show that a wide variety of osmolytes induce expression in , indicating that is a genuine osmo-inducible gene. These results have important biotechnological implications for the development of novel cyanobacterial biofertilzers and transgenic plants with improved resistance to salinity.