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Oscillatoria anguistissima rapidly adsorbs appreciable amounts of cobalt from the aqueous solutions within 15 min of initial contact with the metal solution. O. anguistissima showed a high sequestration of cobalt at low equilibrium concentrations, and it followed the Freundlich model of adsorption. The adsorption is a strongly pH-dependent and temperature-independent phenomenon. The presence of Mg2+ and Ca2+ (100-200 ppm) resulted in decline in Co2+ adsorption capacity of Oscillatoria biomass. Sulphate and nitrate (0. 75-10 mM) drastically reduced the extent of Co2+ biosorption. The biosorption of cobalt is an ion-exchange process as the Co2+ binding was accompanied by release of a large amounts of Mg2+ ions. Na2CO3 (1.0 mM) resulted in about 76% desorption of Co2+ from the loaded biomass.

Oscillatoria anguistissima rapidly adsorbs Cu2+ from aqueous solution. The adsorption of Cu2+ followed Freundlich Isotherm, and the amount of Cu2+ removed from solution increased with increasing Cu2+ concentration. The adsorption is pH dependent, and maximum Cu2+ removal occurs at pH 5. Of the various pretreatments, HCl treatment of the biomass increased the capacity for Cu2+ removal. Presence of Mg2+ and Ca2+ resulted in decline in the Cu2+ adsorption capacity of Oscillatoria cells. This species could also effectively remove Cu2+ from mine water containing 68.4 microg/ml of Cu2+ at pH 3.45.

Oscillatoria anguistissima could tolerate 50 ppm ZnSO4 x 7H2O, and a zinc-tolerant strain with maximum tolerance concentration (MTC) of 100 ppm ZnSO4 x 7H2O was obtained by stepwise transfer to higher concentrations. The adaptation was irreversible even after three generations in metal-free medium. In the presence of metal, the tolerant strain grew with a shorter lag period of 4 days as against 6 days in the case of the wild strain. The tolerant strain had higher MTC than that of the wild strain for other metals also, viz., Ni2+, Co2+, Cu2+ and Cd2+. The zinc resistance in the tolerant strain was a result of reduced uptake, since around 42% of the total metal was present on the surface as against only 30% in the wild strain. The calcium-stimulated uptake, as observed in the wild strain, was absent in the tolerant strain. Ultrastructural comparisons revealed no structural change in the tolerant strain on exposure to zinc, whereas in the wild strain a thick extracellular matrix was observed.

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