Isolation and characterization of carcinogenic chromium reducing pseudomonas soli from soil of Buriganga riverbed

Abstract

Hexavalent Chromium is a heavy metal which possesses carcinogenic and mutagenic property and causes various serious diseases such as skin cancer, lung cancer, pulmonary congestion etc. It is an important component in various industries like leather, tannery, dye, stainless steel etc. and so they are being freed every day without any treatment and making the natural environment very hazardous for the human health. It has become an obligation to reduce the hexavalent Chromium from the natural environment to preserve the earth. A strain from soil sample named Pseudomonas soli has been identified as being capable of reducing carcinogenic hexavalent Chromium to trivalent Chromium. The strain was isolated from Buriganga River bed soil. Nutrient agar medium was employed which was supplemented with hexavalent Chromium in the form of potassium chromate. By purification and subculture on nutrient agar plates containing different concentrations of Chromium, the isolate was obtained. 16S rRNA gene analysis was done to find out its identity. The strain was then subjected to further experimental procedures such as DPCZ base bioremediation assay. Bioassay was carried out at three temperatures: 25°C, 37°C and 42°C and at each temperature, Chromium reduction was seen at three different pH 5.5, 7 and 8.5. It was observed that, the bacterial strain was able to reduce Chromium completely at temperature and pH of 37°C, pH 8.5 and at temperature 42°C, in both pH 7 and 8.5. However, the highest rate of reduction was seen at 42°C at pH 7. Therefore, 42°C, pH 7 is its optium temperature for reduction. Minimum Inhibitory Concentration (MIC) of Chromium (VI) on isolate’s growth pattern and antibiotic resistance profile of the isolate were also deduced. MIC was found to ne 70 mM. The strain demonstrated multiple resistances to antibiotics which included Penicillin, Amoxycillin, Cefixime and Cefuroxime sodium. Moreover, it was seen after study that the bacteria under consideration can withstand up to high concentration of Chromium (upto 69mM) which demonstrates its capacity to survive in very adverse condition. Information gathered from this project confirms that the bacteria is capable of reducing hexavalent Chromium.