Molecular detection of Pseudomonas spp. in agricultural soils

AGARAS B; WALL LG; VALVERDE C

Carlos Paz, Argentina

Congreso; VI Congreso Argentino de Microbiología General; 2009

Among the so-called plant growth promoting rhizobacteria (PGPR), members of the Pseudomonas genus have been isolated and identified worldwide as potentially plant probiotic microorganisms based on their properties to antagonize phytopathogens, induce systemic acquired resistance and increase phosphate availability. Little is known about the dynamics of pseudomonads population in agricultural soils under the influence of biotic and abiotic factors. As part of a national consortium to study soil biology and its relationship with productivity (the BIOSPAS project), our lab began to characterize culturable and unculturable pseudomonads in agricultural soils. To this end, molecular methods are rapid, specific and comprehensive enough to approach such ecological issues. Based on bibliography and available gene sequences, we have selected two markers to detect pseudomonads in soil samples, oprF and gacA, which encode the major non-specific porin and a response regulator involved in post-transcriptional regulation of gene expression, respectively. Oligonucleotides were designed to set up PCR-RFLP protocols and were first validated with pure cultures of type strains, then applied to soil isolates obtained by selective growth on Gould’s S1 medium. The results obtained so far with yet uncharacterized soil isolates indicate that oprF and gacA will be useful targets for studying pseudomonads diversity with culture-independent methods as PCR-DGGE.