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.
Wetland microbial ecology
Microorganisms are vitally important to wetland processes and the main drivers of organic matter decomposition and nitrient mineralization. We've carried out a number of different 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. Generally, we characterize the wetland microbial communities using molecular techniques and determine their activity using enzymatic approaches. We've looked at changes in community structure and activity with depth, as well as the microbial response to factors such as salinity, drainage, and nutrient amendment.
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 (primarily extracellular enzyme activity) 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. An off-shoot of this research is the area of bacterial biogeography and in collaboration with Dr. Cliff Ochs, my lab is investigating the biogeography of bacterial communities in large rivers of the Mississippi RIver Basin.