In the present study, we intended to remediate Cr(VI) with alkaliphilic bacteria Paenibacillus pabuli (JX561107) and Bacillus cereus (JX561108) isolated from alkaline industrial contaminated soil in Pondicherry. The isolated bacteria were tested for the removal efficiency of hexavalent chromium at different concentrations (50 mg/L, 200mg/L, 400mg/L). At 50 mg/L of hexavalent chromium concentration, Paenibacillus pabuli and Bacillus cereus were found to be highly efficient in removing Cr(VI) in 72 hrs at the inoculum rate of 1% of overnight grown bacterial cultures. The isolates could remove 98% and 74% of Cr(VI) within 72 hrs of treatment at 9.5 pH. When the concentration of the Cr(VI) was increased to 400 mg/L, there was a gradual decrease in Cr(VI) removal. SEM images were obtained from the tested bacteria to observe the bacterial cell surface for the changes in the morphology and EDX analysis were also carried out to confirm whether the adhered particles are of chromium.

Arsenic (As) is a renowned threat to the environment and human well-being. Its concentration is increasing year after year in several countries. The utmost pretentious are mining regions of India, as per government surveys and available research findings. Population residing near mining regions are bounded to consume arsenic tainted water in their routine life and evolve various hazardous health problems. Besides many physicochemical techniques at hand for its purification, none are promising. The microbial mediated arsenic detoxification involving oxidation/reduction and extrusion by a membrane-associated efflux pump may perhaps financially acuity and a promising method for bioremediation. The arsenic richness in mining regions triggered the evolution of bacterial cells to come up with a potential mechanism to survive in As rich environment. Microbial extrusion strategy of As in both As3+ and As5+ forms may also be involved in increasing As in abandoned mining regions in underground water. So, to understand the involvement of these bacterial cells in the increment of As in these regions the present study was performed by personally visiting these sites and conversation with local residents. We have witnessed many jaw-dropping truths about As exposure risk to humans and domesticated animals, which has been discussed in this article. This review comprehensively summarizes current studies associated with arsenic exposure, environmental dispersal and its bioremediation through arsenic metabolizing bacteria covering recent developments, pathways, action mechanism and understanding arsenic metabolizers with the depiction of future prospects on arsenic bioremediation from contaminated systems.

Chromium (Cr), a chemical agent, has long been used extensively in leather tanning. Hexavalent chromium (Cr-VI) found in tannery effluent is highly toxic, carcinogenic and mutagenic to humans. Transformation of Cr-VI to its trivalent counterpart, Cr-III, is the basic process in its detoxification, and microbial transformation of Cr-VI to Cr-III has been one of the most widely studied forms of Cr bioremediation. This study aims to explore the ability of naturally occurring bacteria in reducing and detoxifying Cr in vitro and also from tannery effluent. Five efficient Cr reducing and detoxifying bacteria were isolated from tannery effluent, their morphological, cultural, physiological and biochemical characteristics investigated. They were identified as Aeromonas eucrenophila, Bacillus megaterium, B. carboniphilus, B. licheniformis and B. subtilis. Coincubation of the isolates with varying concentrations of potassium dichromate (K2Cr2O7), a Cr salt, in minimum salts medium, pH 7 revealed notable reduction and detoxification of Cr within 24-72 h as determined by 1,5-diphenylcarbazide colorimetric method and atomic absorption spectrophotometry, respectively. The isolates exhibited substantial resistance or tolerance to 125 to 500 ppm K2Cr2O7. Bacterial detoxification or reduction of was increasingly increased as the incubation period increased from 24 to 48 or 72 h and substrate concentration increased from 125 to 250 or 500 ppm. Most of the isolates exhibited increased reduction and detoxification at 37?C compared to that at 30?C or 45?C, and at pH 7 or 8 compared to that at pH 5 or 6. Furthermore, all the isolates exhibited highest detoxification or reduction when peptone was used as carbon source instead of glucose or ammonium acetate. In a chosen or optimized condition of 37?C temperature, pH 7, 125 ppm K2Cr2O7 concentration and 48 h incubation period, most isolates exhibited 85-99% Cr reduction and detoxification from tannery effluent. It was, therefore, inferred that the isolates have potential as biological agent in reducing and detoxifying Cr from industrial effluent.