This Article Full Text Full Text (PDF) Other Versions of this Article: AEM.01892-06v1 73/22/7308    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Flores-Mireles, A. L. Articles by Holguin, G. Search for Related Content PubMed PubMed Citation Articles by Flores-Mireles, A. L. Articles by Holguin, G. Agricola Articles by Flores-Mireles, A. L. Articles by Holguin, G.

Molecular Characterization of Diazotrophic and Denitrifying Bacteria Associated with Mangrove Roots

Centro de Investigaciones Biológicas del Noroeste CIBNOR, Mar Bermejo no. 195, Colonia Playa Palo de Santa Rita, La Paz, BCS 23090, México,¹ Department of Microbiology, Cornell University, Ithaca, New York 14853²

Received 8 August 2007/ Accepted 27 August 2007

An analysis of the molecular diversity of N₂ fixers and denitrifiers associated with mangrove roots was performed using terminal restriction length polymorphism (T-RFLP) of nifH (N₂ fixation) and nirS and nirK (denitrification), and the compositions and structures of these communities among three sites were compared. The number of operational taxonomic units (OTU) for nifH was higher than that for nirK or nirS at all three sites. Site 3, which had the highest organic matter and sand content in the rhizosphere sediment, as well as the lowest pore water oxygen concentration, had the highest nifH diversity. Principal component analysis of biogeochemical parameters identified soil texture, organic matter content, pore water oxygen concentration, and salinity as the main variables that differentiated the sites. Nonmetric multidimensional scaling (MDS) analyses of the T-RFLP data using the Bray-Curtis coefficient, group analyses, and pairwise comparisons between the sites clearly separated the OTU of site 3 from those of sites 1 and 2. For nirS, there were statistically significant differences in the composition of OTU among the sites, but the variability was less than for nifH. OTU defined on the basis of nirK were highly similar, and the three sites were not clearly separated on the basis of these sequences. The phylogenetic trees of nifH, nirK, and nirS showed that most of the cloned sequences were more similar to sequences from the rhizosphere isolates than to those from known strains or from other environments.

Published ahead of print on 7 September 2007.