Lead Toxicity, Adsorption and Resistance in Chlorella Sp.

Abstract

These days, unicellular green microalgae have been widely used for removal of toxic heavy metals from contaminated soil and water bodies. In the present investigation, a lead resistant PbR-11 strain isolated from Chlorella sp. by EMS mutagenesis was compared against the wild type (WT) of the same species for Pb²⁺ accumulating capacity. Growth of both the tested algal cells, PbR-11 and WT (control) were found to be retarded with increasing Pb²⁺ concentrations in the medium. However, higher ID₅₀ value of the PbR-11 exhibited some degree of resistance to the metal toxicity. When exposed to the liquid medium containing 50 mM Pb²⁺, kinetic experiments showed rapid removal and adsorption of the metal ions in both the algal cells during the first few hours. Compared to WT, the PbR-11 showed significantly higher percentage removal and adsorption of Pb²⁺ at 15 minutes and 48 hours interval of time respectively. Extracellular Pb²⁺ adsorption was found significantly higher than intracellular uptake in the tested algal cells although both the processes occurred simultaneously. Total Pb²⁺accumulation and distribution between the external and internal cell fractions of the PbR-11 were significantly higher to that of the WT. Thus, the strain appeared more useful for remediation of contaminated sites.

DOI: http://dx.doi.org/10.3126/on.v10i1.7778