Molecular Markers and Phage Typing as a Tool for Diversity Estimation of Rhizobia

Rhizobia are a widely distributed and abundant soil bacteria belonging to the alpha subclass of the Proteobacteria. The aim of this study was the estimation of rhizobial diversity in different genera using several molecular markers for genomic fingerprinting and the detection of certain symbiotic properties of rhizobia. Phage typing was done in order to detect different susceptibilities to attack by specific bacteriophages. In Serbia rhizobia showed a high level of diversity in genomic fingerprints generated with RAPD (randomly amplified polymorphic DNA-PCR) or rep-PCR (repetitive extragenic palindromic PCR), with primers binding to interspersed repetitive sequences (REP, ERIC and BOX). Together, RAPD and rep-PCR data provide an estimation of a large range of diversity, from intrageneric to strain levels, concerning different rhizobial genera nodulating legumes in Serbia. Two molecular markers were used for detection of symbiotic features of rhizobia: nodulation (nod) genes and genes encoding dinitrogenase reductase enzymes (nifH). Phage typing relies on the presence or absence of particular receptors on the bacterial surface, which are used by the virus to bind to the bacterial wall. Rhizobia phage typing revealed high specificity at the strain level and different patterns of resistance/susceptibility to bacteriophages were obtained.