Biogeographical diversity of leaf-associated microbial communities from salt-secreting Tamarix trees of the Dead Sea region.

The leaves of Tamarix, a salt-secreting desert tree, form an extreme niche that harbors a unique microbial community. In view of the global distribution of this tree, its island-like phyllosphere is highly suitable for studying microbial diversity along geographical gradients. Here we present an analysis of microbial community diversity using leaf surface samples collected at six different sites, on both sides of the Dead Sea, over a period of one year. Biodiversity analysis of denaturing gradient gel electrophoresis (DGGE) patterns of the bacterial 16S rRNA gene revealed a significant degree of bacterial community similarity within trees sampled at the same site, much higher than the similarity between trees from different geographical locations. Statistical analysis indicated that the degree of similarity was negatively correlated with the distance between sampling sites, and that a weak correlation existed between diversity and leaf pH.

Drop-size soda lakes: transient microbial habitats on a salt-secreting desert tree.

We describe a hitherto unrecognized bacterial community, inhabiting the leaf surfaces of the salt-excreting desert tree Tamarix. High temperatures, strong radiation, and very low humidity dictate a daytime existence in complete desiccation, but damp nights allow the microbial population to proliferate in a sugar-rich, alkaline, and hypersaline solution, before drying up again after sunrise. The exclusively bacterial population contains many undescribed species and genera, but nevertheless appears to be characterized by relatively limited species diversity. Sequences of 16S rRNA genes from either isolates or total community DNA place the identified members of the community in five bacterial groups (Actinobacteria, Bacteroidetes, Firmicutes, alpha-, and gamma-Proteobacteria); in each of these, they concentrate in a very narrow branch that in most cases harbors organisms isolated from unrelated halophilic environments.