Comparative study on phosphatase activity of four rice field cyanobacterial strains and their ecological implications
Comparative studies on phosphatase activities of four rice field isolates from India and Bangladesh showed great variation in induction time, and the pattern of enzyme activity in relation to growth. Induction of phosphomonoesterase (PMEase) activity was earliest (2 days) in the Indian isolate Calothrix anomala strain 182 that was maintained in high P concentration in the culture medium. The inductions in the other three strains from Bangladesh (Nostoc 616, Fischerella 612, and Calothrix 604) maintained in low P were between 3-4 days. Comparison of Km and Vmax values early in growth phase, after induction and late in the growth phase showed that the affinity of both PMEase and PDEase for the substrates was higher in early growth phase than in the later stage. The presence of significant phosphatase activity in strain 182 despite its exposure to high levels of P suggests that this cyanobacterium does not lose the capacity to form phosphatase enzymes even under those elevated conditions. Presence of cyanobacterial phosphatases may have very important ecological implications in the rice fields where there is a constant fluctuation in nutrients, especially of phosphate, and organic P may be a frequent alternative to inorganic P as these cyanobacteria are the dominant organisms in the algal/cyanobacterial flora of rice fields.