Endophytic occupation of peanut root nodules by opportunistic Gammaproteobacteria

IBAÑEZ, F., ANGELINI, J., TAURIAN, T., TONELLI, M.L., FABRA, A.

SYSTEMATIC AND APPLIED MICROBIOLOGY

ELSEVIER

Año: 2009 vol. 32 p. 49 - 55

0723-2020

Several bacterial isolates were recovered from surface-sterilized root nodules of Arachis hypogaea L. (peanut)plants growing in soils from Cordoba, Argentina. The 16S rDNA sequences of seven fast-growing strains were obtained and the phylogenetic analysis showed that these isolates belonged to the Phylum Proteobacteria, Class Gammaproteo- bacteria, andincluded Pseudomonas spp., Enterobacter spp., and Klebsiella spp. Afterstorage,these strains became unable to induce nodule formation in Arachis hypogaea L. plants,but they enhanced plantyield. When the isolates were co-inoculated with an infective Bradyrhizobium strain,they were even found colonizing pre-formed nodules. Analysis of symbiotic genes showed that the nifH gene was only detected for the Klebsiella-like isolates and the nodC gene ould not be amplified by PCR or be detected by Southernblotting in any of the isolates. The results obtained support the idea that these isolates are opportunistic bacteria able to colonize nodules induced by rhizobia.