Annual Research Symposium (ARS)

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    Chromium accumulation in Cr (VI) resistant bacteria
    (Book of Abstracts, Annual Research Symposium 2014, 2014) Abewickrama, J.H.G.; Jayarathne, D.L.; Rathnayake, I.V.N.; Gunawardane, M.M.
    Accumulation of Cr(VI) is one of the methods used in bacteria to overcome elevated chromium concentrations. These hyperaccumulators of Cr(VI) are important in bioremediation of Cr (VI) containing wastes. Accumulation of Cr(VI) has been previously reported in Alcaligenes eutrophus CH34, Bacillus subtilis and some Pseudomonas sp. During this study Chromium accumulation of a Cr (VI) resistant Psuedomonas sp., Escherichia coli JM109 and the transformant E.coli JM109 with plasmids extracted from the Cr(VI) resistant Pseudomonas sp. were compared. Cr (VI) accumulation was estimated at 0, 5, 10, 15 mg/L Cr (VI) concentrations after 72 hour exposure time. The cells were subjected to acid lysis and the chromium concentrations were estimated using Atomic Absorption Spectrometry. Cr (VI) accumulation percentages of Cr (VI) resistant Pseudomonas sp. under 5, 10, 15 mg/L Cr (VI) concentrations were 51.38%, 37.46% and 43.13% respectively. Those percentages were 2.6%, 1.54%, and 1.12% for E.coli JM109 while they were 35.58%, 20.06% and 34.03% for the transformant. There is a possibility of chromium accumulation being regulated by Cr (VI) resistant genetic determinants found on plasmids. In addition, the nature of the host that bears the plasmid is also important for the Cr (VI) accumulation mechanism.These hyperaccumulators of Cr (VI) showed potential use in bioremediation of Cr(VI) containing wastes.
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    Plasmid mediated Chromium resistance of bacteria
    (Book of Abstracts, Annual Research Symposium 2014, 2014) Abewickrama, J.H.G.; Jayarathne, D.L.; Rathnayake, I.V.N.; Gunawardane, M.M.
    Plasmid-mediated Cr(VI) resistant bacteria are naturally found in environments contaminated with chromium releasing industrial effluents. These envirnments may contain microorganisms those have genetically regulated mechanisms to overcome elevated Cr(VI) levels. Such mechanisms could be regulated by genes found either in chromosomal DNA or plasmid DNA. In order to understand the exact mechanism and for the possible use of such mechanisms in monitoring and control of heavy metal pollution, it is important to determine whether the resistance is plasmid borne or controlled by chromosomal DNA. There are certain plasmids which contain genes to resist highly toxic hexavalent chromium (chromates and dichromates). Resistance to chromate is determined by decreased chromate transport by the resistant cells. The genes for a hydrophobic polypeptide, ChrA, have been identified in Cr(VI) resistance plasmids of Pseudomonas aeruginosa and Alcaligenes eutrophus.