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Colonization of contaminated soil by an introduced bacterium: effects of initial pentachlorophenol levels on the survival of Sphingomonas chlorophenolica strain RA2 |
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G.M. Colores and S.K. Schmidt
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| The survival of a Sphingomonas species that was introduced into pentachlorophenol (PCP)-contaminated soil was monitored with two complementary methods, a respiration-based assay and a most probably number (MPN) technique. Sphingomonas chlorophenolica strain RA2 is a PCP-mineralizing bacterium that was introduced into soil contaminated with a range of PCP concentrations (0-300 µg PCP g-1 soil). The population of introduced microorganisms was followed for 170 days using a substrate-induced growth-response method and a MPN assay that specifically targets PCP-mineralizing bacteria. Varying the initial PCP concentration resulted in the emergence of three distinct patterns of survival. In soil contaminated with 300 µg PCP g-1 the population of S. chlorophenolica strain RA2 immediately declined following introduction, increased by 200-fold and leveled off by the end of the 170-day incubation. In contrast, populations of S. chlorophenolica strain RA2 declined to levels below detection limits in uncontaminated soil by the end of the experiment. Intermediate PCP concentrations (10-100 µg PCP g-1 soil) resulted in the establishment of S. chlorophenolica strain RA2 that slowly declined in numbers. These results indicate that Sphingomonas chlorophenolica strain RA2 is an effective colonizer of PCP-contaminated soil but will not persist in the absence of PCP. | |||||||||||
Journal of Industrial Microbiology and Biotechnology (1999) 23: 326-331 |
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