Search

The microbial diversity of five unconnected high altitude (≥ 3800 m a.s.l.) wetlands from the Chilean Altiplano was analyzed by a culture-independent approach, using 16 S rRNA gene sequences of different microbial groups. The wetlands (Chungara Lake, Parinacota wetland, Piacota Lake, Salar de Huasco and Salar de Ascotan) differed in terms of habitat type and physicochemical properties. The bacterial communities of these systems were dominated by Bacteroidetes (24-94 % of the clones) and Proteobacteria (Alpha, Beta, Gamma and Delta subgroups) with smaller contributions by the Firmicutes, Actinobacteria, Planctomycetes, Verrucomicrobia, Chloroflexi, Cyanobacteria, Acidobacteria, Deinococcus-Thermus and Candidate Division WS3. Fourteen phylotypes matching Alphaproteobacteria were part of the marine Roseobacter clade, representing new clusters of this group. Archaeal diversity was much lower than that seen for bacteria, and was dominated by Euryarchaeota; however Crenarchaeota were also present. Considering the large differences in microbial community composition between sites and samples, the presence of eleven phylotypes common to two or more habitats is highlighted. The frequent presence of new taxa in different phylogenetic groups in the altiplanic wetlands studied here revealed the unique characteristics of Bacteria and Archaea in these fragile Andean ecosystems.

Enhanced nitrification and coupled denitrification in macrophyte root zones may contribute to the depletion of nitrogen from the rhizosphere and are both critical processes for agriculture and rhizoremediation. We examined one factor likely to affect these processes: the ammonia oxidizing betaproteobacterial community composition, and whether or not it is influenced by plant species (Eleocharis acicularis, Eleocharis palustris, Typha angustifolia) or sediment characteristics. Genes coding for ammonia monooxygenase (amoA) and 16S rRNA of betaproteobacterial ammonia oxidizers were targeted. The betaproteobacterial ammonia oxidizing community in root surface biofilms was distinct from the surrounding rhizosphere sediment. In contrast, communities in rhizosphere and bulk sediment samples were very similar. Our results showed the occurrence of Nitrosomonas europaea-like bacteria nearly exclusively in the rhizoplane biofilms, while sequences affiliated with the Nitrosomonas oligotropha, Nitrosomonas communis and Nitrosospira-lineages were more frequently detected in the surrounding sediment. Our results further suggest that the presence of N. europaea on macrophyte roots depends on the sampling site rather than on the studied macrophyte species. We propose that the rhizoplane of aquatic macrophytes is a natural habitat for N. europaea.