Restoration of effectiveness of R. meliloti ineffective mutants by transduction of high level streptomycin resistance.

Rhizobium meliloti lysine dependent mutant, L5-30lys, was ineffective and this mutation was not cotransducible to lys. Transduction of chloramphenicol and linked temperature sensitive mutations did not change its symbiotic properties. Subsequent transduction of high level streptomycin resistance restored its effectiveness. Streptomycin resistance marker was linked to chloramphenicol resistance and temperature sensitive markers.