Sucrose degradation in salt-treated cyanobacteria.

NISHI, CN; KOLMAN, MA; VARGAS, W; SALERNO, G

Porto, Portugal

Congreso; 14th International Symposium on Phototrophic Prokaryotes; 2012

INTERNATIONAL SCIENTIFIC COMMITTEE FOR THE SYMPOSIA ON PHOTOTROPHIC PROKARYOTES

All organisms have to cope with the constantly changing environment in order to survive, and cyanobacteria are by no means the exception to that. In particular, cyanobacteria can grow under a wide range of environmental conditions, including salinity. Stenohaline cyanobacteria (with low salt tolerance) accumulate various low molecular osmolytes mainly sucrose (Suc), trehalose and sucroglucans. Suc is one of the mosdt abundant dissacharide in nature and was reported to be presente in oxygenic photosyntetic organismo. In particular, Suc metabolismo has been biochemically, functionally and physiologically characterized in unicelular and heterocyst-forming cyanobacterial strains. In Anabaena sp. PCC 7120, Suc can be hydrolysed by two alcaline-neutral invertase isoforms (Inv A or InvB) or cleaved by sucrose synthase (SuSA). In contrast, in unicellular strain Microcystis aeruginosa PCC 7806 only SuS is responsible for Suc catabolism. The aim of this study was to investigate the effect of salt treatment on the expression of Suc degradative proteins and the role of InvA and InvB in Anabaena cells submitted to a salt stress. The expression of SuS or Inv encoding genes increase after salt addition. Also InvA and InvB were not essential to cope the stress, when the growth of insertional was determined. However, the accumulation of sucroglucans and glycogen was affected in presence of NaCl. In the case o M. aeruginosa, both Suc accumulation and cleavage by SuS increased with salt treatment, indicating a sugar cycling during stress. Taken together, our results suggest that Suc is not a mere salt response osmolyte and that Suc cycling mechanism may be operating in both filamentous heterocyst-forming and unicellular bloom-forming strains in response to salinity.