Fitness, persistence, and responsiveness of a genetically engineered strain of Trichoderma virens in soil mesocosms
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The genetic stability and ecological persistence of a strain of the filamentous fungus, Trichoderma virens, genetically modified (GM) with a hygromycin resistance gene and a gene encoding an organophosphohydrolase was evaluated over 243 days in soil mesocosms. The GM populations declined over time, a trend similar to the wild-type, parental strain (WT), but was still present at the end of the incubation. Similar population estimates were obtained by plating serial dilutions on selective media or by quantitative polymerase chain reaction (QC-PCR) after 243 days' incubation. However, the absolute population size differed between the two methods by more than a log order of magnitude with QC-PCR being more sensitive. The presence of the WT strain did not adversely affect the persistence of the GM strain. The GM strain stably maintained the transgene and still expressed antibiotic resistance and the ability to degrade organophosphate xenobiotics. Even after the long-term incubation the GM and WT strains rapidly and efficiently colonized freshly added substrates, indicating a high level of responsiveness. 2004 Elsevier B.V. All rights reserved.