Taxonomy is the science that studies the relationships between organisms. It comprises classification, nomenclature, and identification. Modern bacterial taxonomy is polyphasic. This means that it is based on several molecular techniques, each one retrieving the information at different cellular levels (proteins, fatty acids, DNA...). The obtained results are combined and analysed to reach a "consensus taxonomy" of a microorganism. Until 1970, a small number of classification techniques were available for microbiologists (mainly phenotypic characterization was performed: a legume species nodulation ability for a Rhizobium, for example). With the development of techniques based on polymerase chain reaction for characterization, the bacterial taxonomy has undergone great changes. In particular, the classification of the legume nodulating bacteria has been repeatedly modified over the last 20 years. We present here a review of the currently used molecular techniques in bacterial characterization, with examples of application of these techniques for the study of the legume nodulating bacteria.Key words: polyphasic taxonomy, molecular characterization, bacteria, prokaryotes, legume nodulating bacteria, Rhizobium.
Classification of IBV S1 Genotypes by Direct Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) and Relationship between Serotypes and Genotypes of Strains Isolated between 1998 and 2008 in Japan
