Plant microbiomes and phyllosphere communities
Microbial communities associated with roots (the rhizosphere) have been studies in detail but much less is known about the microbiomes of leaves and other above-ground structures (the phyllosphere). Similarly, less research has examined bacterial populations that live inside plants (endophytes). We're using molecular and culture-based approaches to examine these communities, asking such questions as how they change over time or how they vary from leaf to leaf. A related area of research is investigating the bacterial communities associated with consumable plants such as salad vegetables and herbal supplements, the latter in an NIH-funded collaboration with Drs. David Pasco and Nirmal Pugh in the National Center for Natural Products Research on the UM campus.
Wetland microbial ecology
Microorganisms are vitally important to wetland processes and are the main drivers of organic matter decomposition and nutrient mineralization. We've carried out a number of studies on wetlands around the world; from coastal wetlands around Lake Pontchartrain, Louisiana, to tropical peat swamp forests in southeast Asia and peatlands in northern Europe. An ongoing area of interest is examining the impacts of tropical storms and hurricanes on Gulf Coast wetlands, especially in the context of saltwater intrusion events. As storms push saltwater into freshwater coastal marshes there can be significant changes to both the activity and composition of the sediment microbial community, and we're working to elucidate the implications of those effects along the U.S. Gulf Coast. We're also investigating the importance of the sediment microbial community in promoting salinity tolerance in wetland vegetation.
Bacterial biogeography and spatial patterns in structure and function
While humans tend to sample on scales that are convenient for us, microorganisms don't necessarily follow that pattern. We've been developing and using geostatistical techniques to examine fine-scale spatial heterogeneity in microbial processes and community structure in soils and other systems. This area of research is essentially landscape ecology, but our landscapes may be no more than a few cm across. We've looked at fine scale patterns in microbial activity across the surfaces of decomposing leaves, and how rainfall or fire can change spatial patterns of enzymatic activity in soil. A related area of research is in the field of bacterial biogeography, and we're examining the biogeography of plant-associated bacterial communities and, in an NSF-funded collaboration with Dr. Cliff Ochs in the UM Department of Biology, we're looking at the biogeography of bacterial communities in large rivers of the Mississippi RIver Basin. Both of those areas of research are also examining temporal changes in bacterial assemblages, over both long and short periods of time.
Species, spatial, and temporal patterns in animal microbiomes
The microbiomes of animals are critically important to the host organisms physiology and development. In collaboration with Tim Colston, a former doctoral student in Brice Noonan's lab we've investigated species and spatial patterns in the microbiome of reptiles, with research in North, Central, and South America, as well as Ethiopia. We're also looking at the microbiomes of invertebrates, examining how the microbiome of insects with aquatic larval stages changes during metamorphosis and how the microbiome of freshwater mussels is influence by host species and environmental conditions.