My research seeks to harness the power of modern molecular methods to investigate:

   • The diversity and biogeography of microbes in terrestrial and underexplored environments.
   • How biotic and abiotic environmental characteristics influence the structure of soil microbial communities.
   • The interrelatedness of microbial organisms in terrestrial and symbiotic systems.
   • How knowledge of microbial systems can be applied to agricultural efficiency, environment improvement,
     sustainability, and human health.

Broad-scale diversity patterns of microbial communities and linkages to soil processes

  Development of modern culture-independent techniques and bioinformatics has facilitated dramatic advances in the field of microbial ecology, and has fueled a resurgence of theoretical thinking within the discipline. An important aspect of building a theoretical framework for microbial ecology is discerning patterns that apply universally to communities of microbes in the natural environment. Despite recent progress, we still have inadequate understanding of biogeographic-scale patterns for microbial diversity, variables regulating the structure of these communities, or identities of specific microbes involved soil processes, such as nutrient cycling. I have been involved in numerous projects using contemporary molecular approaches to carry out broad-scale surveys of diverse terrestrial microorganisms with the aim of understanding their ecology and biogeography. This work has included investigations of: fungi of biological soil crusts; microorganisms (archaea, bacteria, fungi, and other microbial eukaryotes) of the soil environment; and bacteria of indoor environments. I have also worked developing network analysis techniques for elucidating co-occurrence patterns and ecological rules guiding assembly of microbial communities, as well as linking these communities to soil processes. Along with collaborators from the African Soil Information Services (AfSIS, Nairobi, Kenya) and Colorado State University (Diana Wall), I have been involved in the first ever continental-scale assessment of total soil biodiversity in Sub-Saharan Africa (Surveying Unexplored Soil Biodiversity in Sub-Saharan Africa).

Microbial organisms of symbiotic systems

  Classic symbioses once thought to represent simple dual-partnerships are now being recognized as unique niches where numerous interactions occur between diverse microbial populations and their symbiont hosts. Investigations focusing on bacteria of symbiotic systems have demonstrated extreme genome reductions for these symbionts, which represent the threshold of cellular evolution. Recent studies are beginning to elucidate functional roles of microbial symbionts, while metagenomic sequencing promises to provide extraordinary insight into gene interactions among microbial consortia of symbioses as well as the reductive evolutionary process. I have been working on a series of projects exploring diverse microbes of symbiotic systems using lichens (classically held as a mutualism between fungi and green algae and/or cyanobacteria) as model systems. Toward this end, I have produced the first high-throughput surveys of bacteria as well as eukaryotes associated with lichens. In addition to providing further evidence on the role of bacteria within these systems as well as the consistent presence of fungal lichen-associates, this work has also shown lichens likely rely on assemblages of microbes from multiple lineages for nitrogen and phosphorus nutrition.

Exploring and documenting fungal diversity of natural environments

  There is an enormous wealth of fungal diversity, and it has been estimated that as little as 5% of all Earth's fungal species have been described. Although fungi are the primary decomposers of biomass in terrestrial ecosystems, key players in global carbon, nitrogen, and phosphorus cycling, and are important symbiotic partners of plants and animals, we still have only rudimentary knowledge of fungal diversity, ecology, biogeography, and environmental factors that structure fungal communities. The field is ripe for comprehensive studies addressing these considerable knowledge gaps. Throughout my career I have maintained a strong interest in mycology, and I continue to pursue projects seeking to gain insights into fungal diversity and ecology. I have long been involved in the study of fungal components of biological soil crust, having carried out some of the first molecular surveys of crust fungi. Recently, my research has expanded to more broadly investigate patterns of fungal diversity of terrestrial systems. I have also been involved in developing online resources for documenting fungal diversity within the United States. These include the Mycology Collections data Portal (MyCoPortal) and the Arizona Mycota Project (AMP).