Characteristics of mercury-resistant bacteria isolated from river water
1990
Chung, H.M. | Kim, S.J. (Seoul National Univ., Seoul (Korea Republic). Coll. of Natural Sciences) | Kho, Y.H. (Korea Advanced Inst. of Science and Technology, Seoul (Korea Republic). Genetic Engineering Research Center)
In samples taken from mouth of the Nakdong River, mercury-resistant bacteria grown on the media supplemented with oer 20 ppm of mercuric chloride were below 0.3 % of all aerobic heterotrophs. Among them, seven strains grwon over 100 ppm of mercuric chloride were isolated and all were identified as Pseudomonas. The toxic effect of mercury on the growth of the most resistant strain N14 was influenced by the organic compounds and concentration. The growth and physiological activity to N14 strain were affected by toxic mercury in the early stage: The viable count and glucose turnover rate of N14 strain dropped to the lowest level as soon as the bacteria came into contact with mercury. During the extended lag period, however, bacteria accommodated to the stress and the viable count and glucose turnover rate increased. After the lag period, bacteria began to proliferate and their growth reached similar level to that of control. In crude extracts of N14 strain growth in nutrient browth containing 10 micro M HgCl2, a mercuric ion dependent oxidation of NADPH was demonstrated. Therefore the mechanism of mercury-resistance of the N14 strain involved the elimination of the mercury from growth media. In the N14 strain which a wide range of resistance to antibiotics was observed in, four multiple plasmids were detected. As a result, the supposition that N14 strain has a plasmid-encoded enzyme system may be quite within the realms of possibility
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