Diverse microbial communities live in the gut regions of animals. The precise ecological and evolutionary circumstances that govern relationships between hosts and their gut communities is unclear. In this study, we hypothesize that host feeding strategy shapes the microbial communities within the gut systems of insects. We collected five insect species from the Sevilleta National Wildlife Refuge that exhibited herbivorous, detritovorous and carnivorous diets.
The McMurdo Dry Valleys in Antarctica (MCM) forms one of the most extreme deserts on Earth. It consists of a mosaic of permanently ice-covered lakes, ephemeral streams, exposed soils, and glaciers. Microorganisms are the only life forms occupying these landscape units. Given the relatively low and seasonal growth rates of these organisms, we contend that the distribution of microorganisms within this environment is controlled by physical factors.
Denitrification is a key step returning nitrogen from soils to the atmosphere. The primary denitrifiers in most ecosystems are heterotrophic bacteria. Although, fungi are also known to transform nitrogen compounds, such as the production of N2O, but few studies have explored this process in soils. Aridland systems experience high temperatutres and low moisture conditions, favoring fungi in these environments. Thus, we explored the role of fungi and bacteria in denitrification of Sonoran Desert soils.
Ecosystem processes in northern systems depend heavily on inputs of biologically fixed nitrogen (N) from A. tenuifolia, which contributes the majority of N accumulated during boreal forest succession. However because of the high phosphorus (P) demands of this plant, we hypothesize that N-fixation inputs are controlled by the ability of alder to assimilate P through associations with ectomycorrhizal fungi (EMF), which produce enzymes that mobilize organic and recalcitrant P forms.
The Sevilleta LTER is located at the intersection of several aridland ecosystem types. Although it is axiomatic that water is the key limiting resource in aridland ecosystems, most arid land soils are also chronically low in nutrients and organic matter. Resource availability is a function of the frequency and size of precipitation events as well as the time between events. As a consequence, NPP and organic matter decomposition are often decoupled in space and time, and soil nutrient supply rates may limit NPP during periods when soil moisture is sufficient for plant growth.
We examined benthic microbial communities in three contrasting subtidal salt marsh sediments over the course of a year to investigate the relationship between environmental conditions and benthic microbial community structure. Samples were collected monthly from a high energy, sandy beach, a tidal creek bed, and a Spartina alterniflora marsh border. The concentrations and biomasses of benthic microalgae (BMA), total and potentially active bacteria (measured by an enzyme-activated fluorogenic compound), heterotrophic protists, and metazoan meiofauna were measured at each location.
The goal of the Arctic LTER is to predict the future ecological characteristics of Arctic Alaska based upon our knowledge of the controls of ecosystem structure and function as exerted by physical setting and geologic factors, climatic factors, biotic factors, and the changes in fluxes of water and materials from land to water.
Impacts of microbial competition, coevolution, and plant-microbe feedbacks on plant productivity and microbial communities in soil
Plant diversity has been studied extensively for its impact on a few basic measures, such as biomass production. However, relatively little is understood about interactions between plant diversity and microbial communities. Through removal of natural enemies with pesticide treatments, we found that foliar fungi have a significant impact on plant productivity, and that the impact is greater at higher than at lower plant diversity.
Much is known about the spatial and temporal distribution of macro-organisms and their activity rates. However, little is known about the spatial variability of microbial communities in lakes. In this study, we examined the spatial variability in both bacterial community composition and activity rates in Toolik Lake, Alaska. Community composition was characterized using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified rDNA, and activity rates were measured by uptake rates of 14C-leucine.
Impact of Agricultural Practices on Bacterial Carbon Use Efficiency
Z. M. Lee and T. M. Schmidt
Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI