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. variabilis SA(0), A. variabilis SA(1), Nostoc muscorum SK and N. muscorum DOH were immobilized in polyurethane foam (PUF) and examined for ammonia excretion, growth and nitrogenase activity. Good growth was estab-lished in three weeks, after which the PU foam-immobilized cyanobacterial cultures were treated with Bavistin, a systemic fungicide, at 5 p.p.m. Ammonia 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 AS-DS and A. variabilis SA(1) recorded a higher protein content with Bavistin treatment. The chlorophyll-a content of A. variabilis SA(0), A. azollae AS-DS, N. muscorum SK and N. muscorum DOH was significantly increased. A.variabilis SA(1) recorded higher C-allophycocyanin and C-phycoerythrin. Carotenoid content was increased in A. variabilis SA(1), A. azollae AS-DS, A. azollae SK6 and N. muscorum SK. The cyanobacterial cultures A. variabilis SA(1) and N. muscorum SK have registered significantly higher total carbohydrate levels on treatment with Bavistin.