Toxic chromate reduction by resistant and sensitive bacteria isolated from tannery effluent contaminated soil

Abstract

Bacterial strains ZA-6, W-61, KS-2 and KS-14 were isolated from agricultural soil irrigated with tannery effluents and subsequently identified by 16S rDNA sequencing as Stenotrophomonas maltophilia, Staphylococcus gallinarum, Pantoea sp. and Aeromonas sp., respectively. All isolates were examined for their resistance to hexavalent chromium and other heavy metal ions. The bacterial isolate S. maltophilia ZA-6 and S. gallinarum W-61 were resistant to 16.5 and 12.4 mM of potassium chromate, respectively, whereas Pantoea sp. KS-2 and Aeromonas sp. KS-14 were found to be sensitive to potassium chromate. S. maltophilia ZA-6 and S. gallinarum W-61 completely reduced 500 μM Cr 6+ to Cr 3+ within 56 h, while chromate-sensitive isolates Pantoea sp. KS-2 and Aeromonas sp. KS-14 exhibited poor chromate-reducing activity. Chromate reduction was severely affected in the presence of the metabolic inhibitors sodium cyanide and sodium azide. Sodium cyanide completely inhibited chromate reduction in each isolate, whereas 1 mM sodium azide and 10 mM sodium sulfate affected the inhibition of chromate reduction to varying degrees. The use of 1 mM 2,4-dinitrophenol, an uncoupling agent, stimulated the chromate reduction. The cell-free extract (CFE) of chromateresistant isolates readily reduced Cr 6+ to Cr 3+ , with that of S. gallinarum W-61 showing a K m value of 121.7 μM chromate and a V max of 1.12 μmol/min per milligram protein in the presence of NADH. The chromate-resistant isolates displayed lower Michealis-Menton constant (K m ) values and higher maximum velocity (V max ) than chromatesensitive isolates. These results suggest that chromate resistance and reduction in these bacteria are related.

Reduction of Hexavalent Chromium by Viable Cells of Chromium Resistant Bacteria Isolated from Chromite Mining Environment

“…On prolonged incubation (48 h), control and DNP treated cells completely reduced the 100 M of Cr(VI). Such promoting effect of DNP has also been reported in Burkholderia cepacia [40] and Staphylococcus gallinarum [11] and Arthrobacter sp. SUK 1205 [27].…”

“…Microbial reduction of hexavalent chromium has attracted increased interest, as this process not only relieves the toxicity of chromium but also leads to the precipitation at near-neutral pH for subsequent physical removal [8]. Chromium resistant and reducing bacteria isolated from chromium polluted environments such as tannery effluent and chromite mining environments have played a key role in chromium bioremediation [9][10][11][12][13]. [12][13][14], were used in this study.…”

Optimization of Chromate Reduction by Whole Cells of <i>Arthrobacter</i> sp. SUK 1205 Isolated from Metalliferous Chromite Mine Environment

“…Chromate reduction by suspended cells of bacteria has been demonstrated to be influenced by the initial Cr(VI) concentration [12,18,20,21] of the reduction medium. Chromium reducing ability of the whole cells of SUK 1205 was monitored at Cr(VI) concentrations ranging from 50 to 800 µM and presented in igure 4.…”

Luteimonas aestuarii SA13A as a Novel Chromium Reducing Strain isolated from Tannery Effluent

“…Industrial emissions unfavorably affect the environment, leading to large-scale worldwide destruction of agricultural land and water bodies (Poopal et al, 2009;Alam et al, 2012). Various toxic substances released during industrial processes accumulate in the environment and food chains, thereby upsetting ecosystems and biological processes in many organisms.…”

“…Its oxyanionic form (CrO 4 2− ) is analogous in structure to sulfate and phosphate ions which readily permeates through bacterial and eukaryotic cells resulting in intracellular reduction finally leading to chromate-induced toxicity (Cheung and Gu, 2007;Patra et al, 2010;Asatiani et al, 2004). The presence of chromate in the environment inhibits most microorganisms, but it also promotes the selection of metal resistant bacteria (Alam et al, 2012;Mondaca et al, 1998).…”