Department of Biological Sciences
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Item Copper uptake by free and immobilized cyanobacterium(OUP, 1989) Verma, Sanjay KumarCopper uptake in free and immobilized cells of the cyanobacterium Nostoc calcicola has been examined. The immobilized cells invariably maintained a higher profile of Cu intake rate (12.7 nmol mg−1 protein min−1) over the free cells (6.0 nmol mg−1 protein min−1). The total Cu uptake in immobilized cells was almost two and a half-times more than their free cell counterpart under identical experimental conditions. Also, the immobilized cells showed a stronger positive correlation between Cu adsorption and uptake. The results have been discussed in terms of improved metabolic efficiency of immobilized cells.Item Genetic transformation of glutamine auxotrophy to prototrophy in the cyanobacterium Nostoc muscorum(Springer, 1990) Verma, Sanjay KumarItem Evidence for energy-dependent copper efflux as a mechanism of Cu2+ resistance in the cyanobacterium Nostoc calcicola(OUP, 1991) Verma, Sanjay KumarWild-type Nostoc calcicola carried out oxygenic photosynthesis extremely sensitive to copper. A Cu(2+)-resistant mutant (Cu-R1) of the cyanobacterium grew normally at high concentrations of Cu2+. Its ability to grow under such conditions was found to be due to mutational acquisition of an energy-dependent efficient system of Cu(2+)-efflux, which rendered Cu(2+)-inhibited oxygenic photosynthesis fully reversible.Item Glutamate inhibition of aerobic N2-fixation and its regulation by nitrate and ammonium in cyanobacterium Nostoc muscorum(NISCAIR, 1992) Verma, Sanjay KumarItem pH regulation of growth, photosynthesis, glutamine synthetase activity and micronutrient transport in the cyanobacterium Hapalosiphon welwitschii(OUP, 1992) Verma, Sanjay KumarOptima for growth, oxygenic photosynthesis and glutamine synthetase activity occurred at pH 10, thus suggesting that the cyanobacterium Hapalosiphon welwitschii is an alkalophile. It produced a Cu-Zn efflux system at pH 9 or 10, but not at pH 7 or 8, to relieve photosynthesis from Cu or Zn inhibition. This finding has a bearing on the ecophysiological competence of the cyanobacterium under natural conditions.Item Copper toxicity and phosphate utilization in the cyanobacterium Nostoc calcicola(Springer, 1993) Verma, Sanjay KumarItem Multiple metal resistance in the cyanobacterium Nostoc muscorum(Springer, 1995) Verma, Sanjay KumarItem Co2+, Cu2+, and Zn2+ Accumulation by Cyanobacterium Spirulina platensis(Wiley, 2008) Verma, Sanjay KumarThe Spirulina platensis biomass was characterized for its metal accumulation as a function of pH, external metal concentration, equilibrium isotherms, kinetics, effect of co-ions under free (living cells, lyophilized, and oven-dried) and immobilized (Ca-alginate and polyacrylamide gel) conditions. The maximum metal biosorption by S. platensis biomass was observed at pH 6.0 with free and immobilized biomass. The studies on equilibrium isotherm experiments showed highest maximum metal loading by living cells (181.0 ± 13.1 mg Co2+/g, 272.1 ± 29.4 mg Cu2+/g and 250.3 ± 26.4 mg Zn2+/g) followed by lyophilized (79.7 ± 9.6 mg Co2+/g, 250.0 ± 22.4 mg Cu2+/g and 111.2 ± 9.8 mg Zn2+/g) and oven-dried (25.9 ± 1.9 mg Co2+/g, 160.0 ± 14.2 mg Cu2+/g and 35.1 ± 2.7 mg Zn2+/g) biomass of S. platensis on a dry weight basis. The polyacrylamide gel (PAG) immobilization of lyophilized biomass found to be superior over Ca-alginate (Ca-Alg) and did not interfere with the S. platensis biomass biosorption capacity, yielding 25% of metal loading after PAG entrapment. The time-dependent metal biosorption in both the free and immobilized form revealed existence of two phases involving an initial rapid phase (which lasted for 1–2 min) contributing 63–77% of total biosorption, followed by a slower phase that continued for 2 h. The metal elution studies conducted using various reagents showed more than 90% elution with mineral acids, calcium salts, and Na2EDTA with free (lyophilized or oven-dried) as well as immobilized biomass. The experiments conducted to examine the suitability of PAG-immobilized S. platensis biomass over multiple cycles of Co2+, Cu2+, and Zn2+ sorption and elution showed that the same PAG cubes can be reused for at least seven cycles with high efficiency.