Long and Medium-Term Research: Factors Affecting the Adaptation Period Preceding Aerobic Degradation of Chlorinated Benzenes

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Long and Medium-Term Research: Factors Affecting the Adaptation Period Preceding Aerobic Degradation of Chlorinated Benzenes This award is under the Long and Medium-Term Research at Foreign Centers of Excellence Program, which enables U.S. scientists and engineers to conduct three to twelve months of research abroad at research centers of proven excellence. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support an eleven-month postdoctoral research visit by Dr. Flynn W. Picardal of the University of Arizona to work with Dr. Alexander J. B. Zehnder of the Swiss Institute for Water Resources and Water Pollution Control (EAWAG). Their research project will study the effect of environmental factors on the acclimation period which precedes the biodegradation of mono-, di- and trichlorobenzenes by a microbial population. The factors to be examined include choice of substrate, substrate concentration, presence or absence of co-substrate, and temperature. Experiments will utilize microcosms containing soil, water and/or sediments to examine the interspecies or interstrain movement of genes encoding known degradation pathways. Chlorobenzenes are being used as model compounds in these studies because the biochemistry and genetics of chlorobenzene degradation have already been elucidated. Pseudomonas sp. Strain P51 will be used as a donor organism to provide a source of genetic sequences capable of chlorobenzene degradation. This recently isolated organism (van der Meer et al, 1991) has been shown to have chlorobenzene biodegradation genes grouped into two clusters. The chlorobenzene dioxygenase gene for this organism has been shown to be located on a transposable element. Mutations and genetic rearrangements in the population will be stimulated through the use of known chemical and physical mutagens and other methods. DNA hybridization and polymerase chain reaction (PCR) techniques are among those that will be used to study genetic movement and acquisition of new genetic material. The frequency and extent of such movement will be examined as a function of the varied environmental factors. The award recommendation provides funds to cover international travel and a stipend for eleven months.