Autecological properties of 3-chlorobenzoate-degrading bacteria and their population dynamics when introduced into sediments.
Ecologically significant properties of wild-type and genetically engineered bacteria capable of degrading 3-chlorobenzoate (3-CB) were compared in the laboratory, and isolates were introduced into streambed sediments in microcosms to observe their population dynamics. 3-CB metabolism, growth on algal extract, temperature optima, and ingestion by protozoa were ecological properties considered relevant to the persistence of these bacteria if introduced into nature. Cell-specific Vmax for 3-CB metabolism and cell-specific mineralization rates each spanned approximately 2 orders of magnitude, but isolates did not rank consistently. The Ks for 3-CB metabolism for Alcaligenes sp. BR60 was approximately 40-fold lower than the mean value for the other isolates, which differed only approximately 4-fold among themselves. All isolates grew on an algal extract nearly as well as on tryptone-yeast extract, implying potential for survival on natural metabolic substrates in situ. Most isolates had temperature optima that were 3-15 degrees C higher than maximum stream water temperature (22 degrees C). Ciliates preferentially ingested P. acidovorans M3GY, and either P. putida RC-4(pSI30) or its parent strain were least preferred, but microflagellates did not exhibit consistent preferences. Fluorescent antibodies were prepared against isolates to permit detection of target cells in natural communities. In three different microcosm experiments the cell densities of introduced isolates declined over a period of days. In one experiment, 3-CB additions (100 mg/L) led to increases of P. alcaligenes C-0 and P. acidovorans M3GY cell densities within 1 day, although P. putida RC-4(pSI30) took 4 days. In a second experiment, the persistence of P. putida RC-4(pSI30) and its parent strain P. putida RC-4 were compared and rates of initial population decline were not statistically different. 3-CB addition stimulated the growth of other organisms while densities of the P. putida strains further declined. In a third experiment exposure to 100 mg 3-CB/L slowed the rate of decline of P. acidovorans M3GY densities compared to a 10 mg/L concentration or unamended control. Competition with the native flora was a significant factor affecting the persistence of introduced 3-CB degraders.
Bott
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TL
Stroud Water Research Center, Avondale, PA 19311, USA. tlbott@stroudcenter.org
Kaplan
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LA
D000421:Alcaligenes / Q000502:physiology*; D001673:Biodegradation, Environmental; D002723:Chlorobenzoates / Q000378:metabolism*; D019015:Geologic Sediments; D030781:Organisms, Genetically Modified; D011157:Population Dynamics; D011549:Pseudomonas / Q000502:physiology*; D016019:Survival Analysis; D014874:Water Pollutants, Chemical / Q000378:metabolism*
D002723:Chlorobenzoates; D014874:Water Pollutants, Chemical; C036427:3-chlorobenzoic acid