Effects of 2,4-dichlorophenol, a metabolite of a genetically engineered bacterium, and 2,4-dichlorophenoxyacetate on some microorganisms-mediated ecological processes in soil

Short, K.A.; Doyle, J.D.; King, R.J.; Seidler, R.J.; Stotzky, G.; Olsen, R.H.

Effects of 2,4-dichlorophenol, a metabolite of a genetically engineered bacterium, and 2,4-dichlorophenoxyacetate on some microorganisms-mediated ecological processes in soil

1991

A genetically engineered microorganism, Pseudomonas putida PPO301 (pRO103), and the plasmidless parent strain, PPO301, were added at approximately 10(7) CFU/g of soil amended with 500 ppm of 2,4-dichlorophenoxyacetate (2,4-D) (500 microgram/g). The degradation of 2,4-D and the accumulation of a single metabolite, identified by gas chromatography-mass spectrophotometry as 2,4-dichlorophenol (2,4-DCP), occurred only in soil inoculated with PPO301(pRO103), wherein 2,4-DCP accumulated to >70 ppm for 5 weeks and the concentration of 2,4-D was reduced to <100 ppm. Coincident with the accumulation of 2,4-DCP was a >400-fold decline in the numbers of fungal propagules and a marked reduction in the rate of CO2 evolution, whereas 2,4-D did not depress either fungal propagules or respiration of the soil microbiota. 2,4-DCP did not appear to depress the numbers of total heterotrophic, sporeforming, or chitin-utilizing bacteria. In vitro and in situ assays conducted with 2,4-DCP and fungal isolates from the soil demonstrated that 2,4-DCP was toxic to fungal propagules at concentrations below those detected in the soil.

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