Areal surfaces of plants, the phyllosphere, provide an important ecological niche for microbes in the terrestrial biosphere, constituting the main interface between terrestrial biomass, the atmosphere, and solar radiation. To survive on the surface of leaves, microbes must adapt to a combination environmental stress factors. This is especially true for epiphytes on a salt secreting desert tree such as Tamarix (Eshel). This genus is well adapted to dry conditions through the ability to secrete solutes on to the leaf surface, rendering it extremely saline. Bacteria living on this surface are exposed to elevated salinity, high temperatures, large doses of UV radiation, high alkalinity, and repeated wetting/desiccation cycles. Despite these harsh conditions, large and diverse microbial populations have been found on Tamarix leaves.
We present our efforts to gain an understanding of the composition of this community, its metabolic potential, and the factors that affect them, by the analysis of metagenomic samples of the Tamarix aphylla phyllosphere from a 350 Km North-South transect in Israel. Using a combination of 16S pyrotag-based as well as community shotgun sequencing approaches, our results illuminate a complex community with uniquely enriched genes, strongly affected by the surrounding environment as well as by geographic location, alternating between gram positive and gram negative-dominated compositions. Assembly and clustering has enabled classifying a large portion of metagenomic data into several bacterial, archaeal, fungal and viral genomic bins, providing insights into the different adaptations of each of these groups to this extreme habitat.
