Molecular characterization and in situ detection of bacteria communities associated to rhizosphere soil of high altitude native Poaceae from andean Puna

FERRERO, MARCELA A.; E. MENOYO; M. A. NEGRITTO; M. A. LUGO; M. E FARÍAS; A. M. ANTON; F. SIÑERIZ

MICROBIOLOGICAL RESEARCH

Año: 2009

0944-5013

Cultivation- dependent and –independent approaches were used to analyse the bacteria communities associated to rhizosphere soil samples. Bacteria diversity from phosphorus-limited Puna native grass species was studied along an altitudinal gradient between 3,320 and 3,870 masl. Whole DNA recovered from R2A agar plate cultures and those directly extracted from rhizosphere soil samples were used for the PCR-DGGE analysis of 16S rRNA genes. FISH analysis was also conducted in fixed-rhizosphere soil samples. In any case band richness, estimated by the number of DGGE bands, was low. The band absolute richness differed along the altitudinal gradient at cultivated (H=16.6, p=0.0019) as well as soil bacteria community (H=18.73, p=0.0007). However, when plant metabolic fixing pathways were considered this variable did not show significant differences at both approaches. Overall, we found a dominance of Bacillus and Pseudomonas between sequenced bands. However, Gammaproteobacteria and HGC grampositive were the dominant bacteria groups in mostly of sites (38 and 33 % of DAPI count) determined by FISH. Mean relative frequencies calculated for DAPI/GAM42a and DAPI/HGC65a did not show significantly differences considering altitude and with plant metabolic patterns. On the other hand, LGC grampositive cells could not be detected by FISH in all samples, while approximately 30% of sequences of Bacillus were recovered from DGGE.