Direct characterization of Frankia and of close phyletic neighbors from an Alnus viridis rhizosphere
Résumé
To analyze the population structure of Frankia soil populations, DNA was extracted from an Alnus viridis rhizosphere, PCR-amplified with a primer designed to be specific, and cloned. A PCR-RFLP analysis of the resulting clones showed that none had a pattern close to those expected from an analysis made on Frankia collection strains, on which HhaI, HpaII and HaeIII were found to be the most discriminant restriction enzymes. Sequencing was done on a subset of soil clones and these were compared to DNA data banks. Some sequences were typical of lowGC Firmicutes (Bacillus and relatives), whereas others were typical of highGC Firmicutes (Actinomycetes and relatives). Two of these sequences appear to be in the same line of descent as Frankia and Geodermatophilus and represent as yet uncharacterized soil microorganisms. This shows that the design of specific or generic primers must be refined constantly to lake into account the deposition of such new sequences in DNA data banks.