High diversity of diazotrophic bacteria associated with the carnivorous plant Drosera villosa var. villosa growing in oligotrophic habitats in Brazil

• DOI: 10.1007/s11104-006-9066-7
• Publication Date: 2006-08-23T10:45:08Z
• Authors: U. Albino; D. P. Saridakis; M. C. Ferreira; M. Hungria; P. Vinuesa; G. Andrade
• Keywords: 0303 health sciences; 03 medical and health sciences; 15. Life on land

Drosera villosa var. villosa A. St.-Hil is a carnivorous plant that grows in Brazilian floo- ded soils very poor on nutrients, including low levels of N. Under these conditions, the plant shows vigorous growth, low root number, low number of captured prey (less than 50%) and a great assemblage of bacteria associated with the roots and leaves that grow in N-free medium. These preliminary results have led us to investigate the number of colony forming units (log CFU) in the roots (rhizosphere and endo- rhizosphere) and leaves (phyllosphere and endo- phyllosphere) of D. villosa var. villosa by the tenfold serial dilution technique in two N-free culture media. The results showed that the phyllosphere had 6.65 log CFU g dry leaf -1 and the rhizosphere 6.47 log CFU g dry soil -1 , with the lowest value detected in the endophyllosphere (4.39 log CFU g dry leaf -1 ). Sixty-three different bacteria morphotypes were isolated from the surface and interior of the roots and leaves and the amplification of the DNA with specific prim- ers detected the nifH gene in 34 of those strains. The DNAs of the 34 strains were compared by the BOX-PCR technique and a great diversity was observed, with the bacteria clustering at a final level of similarity of only 12%. The strains were also submitted to the partial sequencing of the 16S rRNA gene and several genera of N2-fixing bacteria were detected, including Bacillus, Burkholderia, Methylobacterium, Paeni- bacillus, Pseudomonas and Sphingomonas.