EFFECT OF THE SYSTEMIC FUNGICIDE, BAVISTIN ON THE NITROGEN STATUS OF CYANOBACTERIA UNDER IMMOBILIZED STATE IN POLYURETHANE FOAM

Symbiotic forms of cyanobacterial cultures, namely Anabaena azollae AS -DS and A. azollae SK6, and the free-living forms, namely A. variabili s SA(0), A. variabilis SA(1), Nostoc muscorum SK and N. muscorum DOH w ere immobilized in polyurethane foam (PUF) and examined for ammonia ex cretion, growth and nitrogenase activity. Good growth was estab-lished in three weeks, after which the PU foam-immobilized cyanobacterial cu ltures were treated with Bavistin, a systemic fungicide, at 5 p.p.m. A mmonia excretion was enhanced by Bavistin, whilst glutamine synthetase activity was markedly inhibited. Bavistin treatment stimulated growth and nitrogenase activity of the cyanobacterial cultures. A. azollae A S-DS and A. variabilis SA(1) recorded a higher protein content with Ba vistin treatment. The chlorophyll-a content of A. variabilis SA(0), A. azollae AS-DS, N. muscorum SK and N. muscorum DOH was significantly i ncreased. A.variabilis SA(1) recorded higher C-allophycocyanin and C-p hycoerythrin. Carotenoid content was increased in A. variabilis SA(1), A. azollae AS-DS, A. azollae SK6 and N. muscorum SK. The cyanobacteri al cultures A. variabilis SA(1) and N. muscorum SK have registered sig nificantly higher total carbohydrate levels on treatment with Bavistin .