Jaysankar De

Publications (14) View all

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  Article: Bioremediation of toxic substances by mercury resistant marine bacteria.

  Jaysankar De, A Sarkar, N Ramaiah
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  ABSTRACT: Bioremediation of toxic substances includes microbe-mediated enzymatic transformation of toxicants to non-toxic, often assimilable, forms. Mercury-resistant marine bacteria are found to be very promising in dealing with mercury, and a host of other highly toxic heavy metals and xenobiotics. In the present studies we have shown that the Pseudomonas aeruginosa CH07 (NRRL B-30604) has been able to degrade a variety of PCB congeners including a complete degradation of CB-126 and CB-181. The culture was able to remove over 70% Cd from growth medium when supplemented with 100 ppm Cd. The same bacterium rapidly biotransformed/removed toxic mercury from wastewater in a bioreactor system.
  Ecotoxicology 06/2006; 15(4):385-9. · 2.36 Impact Factor
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  Article: Aerobic degradation of highly chlorinated polychlorobiphenyls by a marine bacterium, Pseudomonas CH07

  Jaysankar De, N. Ramaiah, A. Sarkar
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  ABSTRACT: Hitherto, aerobic degradation of polychlorinated biphenyls (PCBs) has been reported to be limited to the less chlorinated biphenyls. We report here a marine mercury-resistant bacterium, Pseudomonas CH07 (NRRL B-30604) which was capable of degrading a variety of highly chlorinated congeners of PCBs from the technical mixture Clophen A-50. Of the two most toxic coplanar PCBs present in Clophen A-50, one coplanar pentachloro congener CB-126 and one toxic sterically hindered heptachloro congener CB-181 were found to be degraded completely and the other coplanar tetrachloro congener CB-77 was degraded by more than 40% within 40 h by this microorganism. The apparent absence of bphC in this bacterium leads to the proposal of a different mechanism for degradation of PCBs.
  World Journal of Microbiology and Biotechnology 01/2006; 22(12):1321-1327. · 1.53 Impact Factor
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  Conference Proceeding: HEAVY METAL ACCUMULATION BY CERTAIN AQUATIC MACROPHYTES FROM LAKE SEVAN (ARMENIA)

  L. Vardanyan, K. Schmieder, H. Sayadyan, T. Heege, J. Heblinski, T. Agyemang, J. De, J. Breuer
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  ABSTRACT: General contamination of heavy metals in the environment is a major global concern, which has provoked the emergence of phytoremediation technologies for cleaning aquatic environment. Heavy metals are released into the environment from a wide range of natural and anthropogenic sources. Macrophytes are known as good indicators of heavy metal contamination in aquatic ecosystems and they act as biological filters by accumulating heavy metals from the surrounding environments. Concentrations of heavy metals such as Hg, Cd, Co, Cu, Mo, Ni, Pb, Tl and Zn were measured in macrophytes and water samples from the mouth of five rivers namely; Gavaraget, Argichi, Makenis, Masrik each of them meeting the Lake Sevan, Armenia. The collected plants were Batrachium rionii, Myosotis palustris, Lythrum salicaria, Scrophularia alata, Calamagrostis epigeios, Lepidium latifolium, Glyceria plicata, Veronica anagallis-aquatica, Butomus umbellatus, Sparganium erectum. The highest concentration of Ni (5.5 mg/kg) was observed in Glyceria plicata whereas concentrations (mg/kg) of all other metals were highest (Hg, 0.02; Cd, 0.46; Co, 3; Cu, 18.9; Pb, 6.9; Tl, 0.13 and Zn, 113) in Batrachium rionii. Range and trend in concentrations of Co (<0.5µg/l), Cd (<0.5µg/l), Tl (<0.1µg/l) and Hg (<0.3µg/l) in water samples were similar at all the sites. Occurrence of heavy metals was much higher in macrophytes and water from Gavaraget and Masrik than that of the Argichi and Makenis due to the discharge of sewage into the river Gavaraget and industrial wastewaters into the river Masrik. The fact that the concentrations of different heavy metals in these macrophytes were far higher than in their respective water column indicates to their role in the biogeochemical cycles of heavy metals. This study aimed at understanding the importance of macrophytes in accumulation of heavy metals and suggesting remedial measures for the preservation and restoration of the lake ecosystem.
  The 12th World Lake Conference; 01/2008
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  Article: Characterization of marine bacteria highly resistant to mercury exhibiting multiple resistances to toxic chemicals

  J. De, N. Ramaiah
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  ABSTRACT: Several strains of bacteria unusually highly resistant to mercury were isolated from seawater and marine sediment samples and identified by 16S rDNA sequencing and were also characterized by a battery of biochemical and morphological tests. The bacterial isolates were identified to belong to the genera Pseudomonas, Alcaligenes, Brevibacterium and Bacillus. Many of the chosen isolates were tested for growth in the presence of different heavy metals and a variety of xenobiotics. Growth curves of all six bacteria highly resistant to mercury examined for growth at different concentrations of Hg exhibited prolonged lag phase, during which time necessary physiological adaptations to toxic milieu were undergone. All the strains tested for antibiotic resistance showed little to no effect of antibiotics on their normal growth. Results of this study demonstrate the occurrence of diverse groups of marine prokaryotes capable of high tolerance to mercury with a potential to degrade a variety of toxic heavy metals and xenobiotics.
  Ecological Indicators 07/2007; 7(3):511–520. · 2.69 Impact Factor
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  Article: Occurrence of large fractions of mercury-resistant bacteria in the Bay of Bengal

  De Jaysankar, N. Ramaiah
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  ABSTRACT: As insights from tolerance responses of native microflora are useful in deciphering their involvement in biogeochemical cycling of heavy metals, we enumerated mercury resistant bacteria (MRB) using sea water nutrient agar medium amended with 10 ppm Hg from oceanic and coastal waters of the Bay of Bengal (BOB) during the summer monsoon (July–August 2001) period. MRB were present in all samples and, intriguingly, the MRB percent based on total viable counts (TVC) increased significantly (r = 0.86; P less than 0.001; df = 44) with depth. On an average, MRB contributed to over 20% of TVC on the surface, 12% at 100 m, 35% at 500 m and a staggering 49% at 1000 m. The fact that a major portion of the natural, culturable bacterial flora was mercury-resistant from the offshore regions of the BOB points to the global nature of mercury pollution. The higher percentages of MRB in the offshore waters of the BOB might signify the already prevalent adverse impact of heavy metals on the metabolic performance of heterotrophic microflora.
  Current science 08/2006; 91(3):368-372. · 0.94 Impact Factor