PHENOTYPIC PLASTICITY OF PSEUDOMONAS-AUREOFACIENS (LACZY) INTRODUCED INTO AND RECOVERED FROM FIELD AND LABORATORY MICROCOSM SOILS

The ability of bacteria to alter phenotypic characteristics during the ir survival and persistence in soil complicates the risk assessment of bacterial inoculants, especially those genetically engineered. The pu rpose of this study was to investigate changes in the phenotype of Pse udomonas aureofaciens 3732 RN-LII (lacZY) introduced into and recovere d from wheat roots or soil obtained from the field or laboratory micro cosms. Fatty acid methyl ester (FAME) and Biolog(TM) analyses were use d to characterize the phenotype of 88 isolates obtained from soil coll ected over a 2-year period. There was variation in the relative propor tions of fatty acids found in isolates over the growing season, with F AME profiles of isolates obtained at 14, 28 and 70 days after planting different from isolates obtained at day 0 and day 140. However, these changes were not sufficient to alter the species designation. Similar ly, carbon substrate utilization by isolates varied only slightly over the growing season. In addition, there were few phenotypic difference s found between isolates obtained from rhizosphere or bulk soil, and n o observed differences between isolates recovered from field soil or m icrocosms. Our results indicate that there was little phenotypic drift of this genetically engineered bacterium during its survival in field and laboratory microcosm soils. (C) 1998 Federation of European Micro biological Societies. Published by Elsevier Science B.V. All rights re served.