Intact Soil-Core Microcosms for Evaluating the Fate and Ecological Impact of the Release of Genetically Engineered Microorganisms

Abstract

Intact soil-core microcosms were studied to determine their applicability for evaluating the transport, survival, and potential ecosystem effects of genetically engineered microorganisms before they are released into the environment. Soil-core microcosms were planted with wheat and maize seeds and inoculated with Azospirillum lipoferum SpBr17 and SpRG20a Tn 5 mutants, respectively. Microcosm leachate, rhizosphere soil, plant endorhizosphere, insects, and xylem exudate were sampled for A. lipoferum Tn 5 mutant populations. A. lipoferum Tn 5 populations, determined by most-probable-number technique-DNA hybridization, varied from below detection to 10 6 g of dry root −1 in the rhizosphere, with smaller populations detected in the endorhizosphere. Intact soil-core microcosms were found to maintain some of the complexities of the natural ecosystem and should be particularly useful for initial evaluations of the fate of plant-associated genetically engineered bacteria.