U. Badar et al., Reduction of chromate by microorganisms isolated from metal contaminated sites of Karachi, Pakistan, BIOTECH LET, 22(10), 2000, pp. 829-836
Three bacterial strains, two identified as Pseudomonas stutzeri and one as
a strain of cucurbit yellow vine disease bacterium, isolated from a foundry
soil and a tannery, respectively, in Pakistan, were resistant to up to 1 m
M chromate and anaerobically reduced Cr(VI) up to 100 mu M. The highest rem
oval was by P. stutzeri CMG463: 88 mu mol l(-1) (88% of that supplied; spec
ific rate was 3.0 nmol mg(-1) protein h(-1)), while 58 and 76 mu mol l(-1)
(58% and 76%) were removed by P. stutzeri CMG462 and cucurbit yellow vine d
isease bacterium CMG480, respectively. These isolates were compared to stra
ins isolated from an uncontaminated coastal site in the UK and designated a
s K2 (Pseudomonas synxantha) K3 (Bacillus sp.), and J3 (unidentified Gram-p
ositive strain). Strain K3 was Cr-sensitive, partially lysed by Cr(VI), but
had the highest removal of chromate anaerobically: 92 mu mol l(-1) (92% of
that supplied) at a specific rate of 71 nmol mg(-1) protein h(-1). Analysi
s of cell sections using transmission electron microscopy with energy dispe
rsive X-ray analysis showed intracellular chromium in P. stutzeri but the c
ucurbit yellow vine disease bacterium and the Bacillus sp. precipitated chr
omium extracellularly. The isolates from the Cr-contaminated sites did not
remove more Cr(VI), overall, than Cr-unstressed bacteria, but their toleran
ce to Cr(VI) is potentially useful for bioremediation, particularly since o
ther studies have shown that the two P. stutzeri strains can bioaccumulate
Cu2+.