Index >> Rhizobium and Legume Root Nodulation >>Antibiotic Resistant Markers

Rifamycin binds to one of the subunits of RNA polymerase and thus prevents the transcription of genes to messenger RNA. Streptomycin binds to a ribosomal subunit and prevents protein synthesis. In both the instances, antibiotics alter the molecules. The altered molecules function as specific 'markers' and help in distinguishing rhizobial strains by developing resistance to anyone of these antibiotics. In a mixed population of rhizobia, only those introduced strains which are marked to either rifamycin or streptomycin will grow when plated on antibiotic containing agar medium. However, it should be borne in mind that the antibiotic resistant markers must remain stable and unchanged in symbiotic performance and characteristics that are not common to indigenous soil bacteria.