ABSTRACT
The potential of Nostoc calcicola and its bicarbonate resistant mutant as bioameleorating agent was investigated, using laboratory simulation experiments, in terms of their growth potential, glutamine synthetase (GS) activity, heterocyst frequency and effect on pH of soil. Nostoc calcicola, exhibited a tendency to lower the pH of 'usar' soil significantly and showed better growth and pigment content at 20% soil extract as compared to basal medium. The bicarbonate resistant mutant (HCO(3) (-R)) exhibited a better ability to grow at higher percentage of soil extract (60%), besides bringing about a more significant change in soil pH as compared to wild type. The heterocyst frequency was much higher in the mutant strain, which was not significantly affected by growth in various concentrations of soil extract. The mutant strain holds promise as a potential bioameliorant for 'usar' soil after further evaluation of its reclamative properties at field level.
ABSTRACT
The activity of enzyme carbonic anhydrase (CA) was investigated in two diazotrophic cyanobacteria, Anabaena sp. (ARM 629) and Nostoc calcicola, in the presence of CO2/NaHCO3 and different inhibitors. The CA activity increased when the cells were pretreated with a high concentration of CO2/NaHCO3 and then transferred to ambient level CO2. Maximum activity of CA was observed after 8 h of incubation in light on transfer of cells from high Ci to ambient level CO2, and was low when incubated in dark. Addition of the photosynthetic inhibitor DCMU brought about a differential reduction in CA activity, depending on the carbon source (NaHCO3/CO2). CA inhibitors--ethoxyzolamide (EZ) and acetazolamide (AZ)--inhibited the enzyme activity in both the genera, but the extent of inhibition was greater in Anabaena sp. than in N. calcicola. Such a variation in extent of inhibition/stimulation of CA activity being different in the two genera reflects differences in their inherent potential and genetic background. The relevance of such cyanobacterial strains as CO2 sinks is also discussed.
