IMPAIRMENT OF TRANSPOSON-INDUCED MUTANTS OF RHIZOBIUM-LEGUMINOSARUM

Tn5 mutagenesis was investigated as a technique to genetically mark Rhizobium for soil microcosm studies. Sixteen mutants created by Tn5 insertion or suicide vector integration were analyzed to determine how the mutations affected several phenotypic traits. These included growth rate in culture, symbiotic effectiveness, and competitiveness for nodule occupancy. Seven of 10 Tn5-containing strains and 5 of 6 vector-integrate strains were impaired in one or more phenotypic traits in comparison to their parent. These results illustrate the need to carefully characterize genetically marked organisms instead of assuming the marked organism is simply an antibiotic-resistant strain equal to the parent.