Heavy metal pollution affects environment
adversely and leads to severe implications for both flora
and fauna. In the present work, bacterial strain JS-1 was
isolated with tolerance for different metals such as mercury
(Hg), lead (Pb), cadmium (Cd), nickel (Ni), arsenic (As),
tin (Sn), selenium (Se), zinc (Zn), chromium (Cr) and
copper (Cu). JS-1 showed a significant tolerance for mercuric
chloride (up to 5,000 μ/g) along with an efficient
metal uptake and transformation. Growth of JS-1 was
marginally affected on exposure to high mercury concentration
due to acclimatization of the culture towards mercury.
No mercury was found in cell-free supernatant after
96 h of incubation with 500 μ/g and 1,000 μ/g of mercury
as an active ingredient. Almost all the mercury was
found associated with cell biomass as determined by
hydride generation atomic absorption spectroscopy. Only
60 % of mercury was sequestered in bacterial biomass on
exposure to 2,000 and 5,000 μ/g mercury. As a detoxification
mechanism, nearly 5 % of sequestered mercury was
volatilized by the selected isolate (JS-1). Further X-ray
diffraction analysis of deposited silvery grey biomass
confirmed biotransformation of sequestered mercuric ions
into monovalent mercury (Hg
2Cl
2), a non-bioavailable
form of mercury. Culture was characterized morphologically,
physiologically and biochemically. 16S rRNA gene
sequence of JS-1 revealed its phylogenetic relationship and
98 % homology with
Alcaligenes faecalis
, a Gram-negative
rod-shaped bacterium.
