Browsing by Author "M. Raizada"

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Effect of four heavy metals on the biology of Nostoc muscorum
(Springer-Verlag, 1990) L.C. Rai; M. Raizada; N. Mallick; Yashmin Husaini; A.K. Singh; S.K. Dubey
This study presents the effects of Cr, Pb, Ni and Ag on growth, pigments, protein, DNA, RNA, heterocyst frequency, uptake of NH4+ and N03-, loss of electrolytes (Na+ and K+), nitrate reductase and glutamine synthetase activities of Nostoc muscorum. The statistical tests revealed a direct positive correlation between the metal concentration and inhibition of different processes. Ni was found to be more toxic against growth, pigments and heterocyst differentiation compared to the other metals. Inhibition of pigment showed the following trend: chlorophyll > phycocyanin > carotenoid. No generalized trend for inhibition of macromolecules was observed. The loss of K+ and Na+ as affected by Cr, Ni and Pb was similar but more pronounced for K+ than Na+. The inhibition of physiological variables depicted the following trend: Na+ loss > K+ loss > glutamine synthetase > NH4 uptake > growth > N03- uptake > nitrate reductase > heterocyst frequency. This study therefore suggests that loss of electrolytes can be used as a first signal of metal toxicity in cyanobacteria. However, further study is needed to confirm whether the abnormality induced by nickel (branch formation) is a physiological or genetic phenomenon. © 1990 Springer-Verlag.
Metal induced inhibition of growth, heterocyst differentiation, carbon fixation and nitrogenase activity of Nostoc muscorum: Interaction with EDTA and calcium
(1985) M. Raizada; L.C. Rai
The effects of different concentrations of chromium and lead on survival, growth, heterocyst production, carbon fixation and acetylene reduction of Nostoc muscorum have been studied. Approximately 50% of the algae survived at 68.0 and 72.0 μM concentrations of chromium and lead, respectively. Chromium proved to be more toxic than lead because its sublethal concentration inhibited approximately 82% 14CO2 uptake and 64% acetylene reduction; however, the inhibition of these processes by lead was only 15% and 36%, respectively. Toxicity was found to be reversed by calcium but not by EDTA. It is suggested that calcium plays an important role in ameliorating metal toxicity in Nostoc muscorum.