Research topics and themes
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Wetland microbial ecology
Microorganisms are vitally important to sediment processes in wetlands and are the main drivers of organic matter decomposition and nutrient 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.
Plant-associated bacterial communities
The surfaces of plants are covered with microorganisms. While natural bacterial communities associated with roots have been studied in detail, much less is known about the bacteria associated with leaves (the phyllosphere). 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. We're also looking at the bacterial communities that live inside plants (endophytes). A related area of research is investigating the bacterial communities associated with consumable plants such as salad vegetables and herbal supplements.
Biofilms and bacterial succession
Surfaces immersed in liquid are colonized by bacterial populations (biofilms), and these populations are replaced over time in a process that resembles ecological succession. We can use molecular techniques such as denaturing gradient gel electrophoresis (DGGE) to study these changes and to determine patterns in diversity as the community develops. This area of research links microbiology and microbial ecology to ideas from theoretical community ecology. We're also examining how space (in the form of surface area or particle size) influences the attached biofilm community in aquatic systems, and how biofilms associated with wetland vegetation respond to agricultural runoff containing pesticides and nutrients.
Spatial patterns in microbial community 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. See that projects website for more information.
Arsenic microbiology: While arsenic is toxic to many organisms, a large number of bacteria have genetic mechanisms to resist arsenic. These bacteria are much more common than is generally known, and we've been able to isolate arsenic-resistant bacteria from various aquatic and terrestrial environments. Other research has used bioinformatic techniques to examine the phylogeny of arsenic resistance genes..
Website maintained by Colin Jackson. Last updated 4/15/12