Toxic heavy metals that cause environmental contamination are of increasing economic, public health and environmental significant. 1) Chromium is a heavy metal of particular importance. It is extensively used in industry, which creates contamination to both aquatic (fresh water and marine water) as well as terrestrial life. In general Cr (VI) is considered to be of greatest concern due to studies in mammalian systems that show it to be carcigenic and toxic. 2) Several studies have found that metals influence microorganisms by adversely affecting their growth, morphology, and biochemical activities, resulting in decreased biomass. 3, 4) Despite these toxic stresses, most of the microorganisms have evolved metal resistance, detoxification mechanisms, including volatilization, extra cellular precipitation and exclusion, intracellular sequestration and off course membraneassociated metal pumps. 3, 5)

Microbial based metal remediation realize on the ability of some microorganisms to resist and detoxify metals. Metals, like all elements, are not biodegradable and can only be transformed from one chemical state to another. 6) In laboratory studies, Cr (VI) is actively transported into cells and then intracellularly reduced and effluxed as Cr (III) via the ChrA system. 7) In Pseudomonas spp., Cr (III) then accumulates on the cell wall and outer membrane. 8) Similar processes have been documented for other bacterial species and toxic metals. 9–12) Recently, surface complexation mod-