Effects of Different Levels of Cr concentration on the Growth Behaviour of Selected Chromate - Resistant Bacterial Strains

Abstract

Chromium is one of the most toxic metals widely found in water bodies. The large scale use of chromium in various industrial processes makes these industries potential source of the chromium pollution. The presence of high levels of chromate in the environment also has an inhibitory effect on most microorganisms. The Cr⁺⁶compounds are comparatively more toxic than those of Cr⁺³ due to their higher solubility in water, rapid permeability through biological membranes and subsequent interaction with intracellular proteins and nucleic acids. Cr⁺⁶ is highly toxic to plants, which results in reduced roots, phytomass and photosynthetic pigments, chlorosis, stunting and plant death eventually. Non - biodegradability of heavy metals is responsible for their persistent in the environment and subsequent bioaccumulation in the food chain. Bioremediation of the chromium compounds is of a special interest since this metal has found a variety of industrial application and it causes severe environmental problems due to its extreme toxicity to living organisms. The objective of the present work was to isolate chromate - resistant bacterial strains from the tannery sludge and to assess the bioremediation potential of these strains on the basis of growth response in different Cr concentrations. These strains showed multiple metal and antibiotic resistances. Growth behaviour of these strains was tested by applying different chromium concentration. Chromium accumulation of isolates has great bioremediation potentials and it can also help in removal and recovery of chromium from the sludge and effluent. The results have been discussed in relation to the development of an integrated bioremediation system for the treatment of tannery sludge and effluent.