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Prokaryotic diversity of Biological Soil Crusts in aridlands of North America
Biological soil crusts are mm- to cm- thick, physically coherent assemblages of microorganisms that develop in geographical areas where plant cover is restricted by aridity. They are dependent of microbial photosynthesis during times of water availability. In spite of their global significance, and in spite of their recognized potential for influencing arid land hydrology, erodibility, fertility, and biogeochemical cycling, there has been virtually no efforts to define, characterize and inventory the nature and composition of prokaryotic communities within them. We propose to remedy such blatant lack of knowledge by initiating a survey of prokaryotic diversity (Bacteria and Archea) within biological desert crusts from various sites spanning a gradient of aridity in North America. Due to the magnitude of prokaryotic richness, we will concentrate our survey in organisms that are either abundant in the field or interesting due to their phylogenetic or metabolic novelty.
For this, we will use a mixed approach that will entail molecular methods of microbial community fingerprinting as well as more traditional enrichment, cultivation, characterization and formal description approaches. Community fingerprints will be based on environmental nucleic acid analysis through
Denaturing Gradient Gel Electrophoresis of PCR-amplified 16S rRNA gene fragments, allele recovery, sequencing and phylogenetic analyses. This will result in community fingerprints, an inventory of molecular diversity and, importantly, in the determination of common and widespread ‘phylotypes”. Paralelly, we will initiate enrichment cultivation efforts for a variety of bacterial metabolic guilds, which will be guided by feed-back from our molecular inventories. From a large number of initial isolates, for which we will perform restricted characterization, we will select those that are representative of important natural populations, or otherwise interesting to science. The latter will be submitted to intensive characterization and
formal taxonomic description. Local, accessible repositories will be set up for samples, DNA extracts, and isolated strains. Public repositories will be extensively used for DNA sequence data and well characterized strains. Information gathered during the work will also be processed to unravel patterns of distribution and abundance of desert crust prokaryotes. The establishment of a web-based, publicly accessible database on desert bacteria will be a central part of the project. This database, created with a high inter-linking capability, will manage, store and make available all data obtained during the project, and will centralize otherwise scattered information. The project will also enable a long-term graduate and undergraduate educational effort on bacterial Systematics and Diversity. This project is funded by the National Science Foundation-Biology.
See pictures of biological soil crusts and their habitats
Example of encrusted soils found in Canyonlands National Park, UT.
When undisturbed, soil crusts can become highly pinnacled and biologically diverse.