Studies On Heavy Metal Tolerance In Kocuria Species Bri 36

Abstract

The thesis addresses today s concern of heavy metal removal, describing passive as well as active mechanism by Kocuria sp. isolated from Antarctic oceanic region. Kocuria sp. BRI 36 belongs to Actinobacteria. As per our knowledge, this is the first report on heavy metal bioremediation potential of Kocuria sp. Different mechanisms of heavy metal (Ni2+, Cr3+, Cd2+ and Pb2+) removal were studied during study. Further objectives include studies on cellular, biochemical and molecular aspects of metal tolerance in Kocuria sp. BRI 36. Maximum removal of Cd2+ and Pb2+ by accumulation and Ni2+ and Cr3+ by biosorption was observed. The biosorption equilibrium isotherm was determined by Langmuir model. In all experiments metal estimation was carried out by inductively coupled plasma-optical emission spectroscopy (ICP-OES Agilent model 7700, G3281A). Morphological changes under stress conditions were examined by Field emission scanning electron microscopy (FESEM). Fourier transform infrared spectroscopy (FTIR) was used to confirm interactions between heavy metals and functional groups on the cell surface. Kocuria sp. BRI 36 also has an ability to produce red-orange color pigment. The response of BRI 36 to different heavy metals at different concentrations in terms of amount and color of pigment produced was analyzed and it might prove useful in detection of heavy metal contamination. The isolate under study was also found to produce EPS at high sugar concentration. Its heavy metal tolerance in terms of maximum tolerable concentration (MTC) increases considerably with increase in EPS concentration. Comparative analysis of intracellular protein profiles by SDS-PAGE of metal exposed Kocuria sp. BRI 36 with that of control revealed prominent presence of certain sets of proteins in the sample under Cd2+ stress. Further studies revealed that metal resistance characteristics of Kocuria sp. BRI 36 are independent of extra chromosomal DNA, since the MTC results remained unaltered after plasmid curing.