SUCCESSION OF SOIL MICROBIAL COMMUNITIES DURING ECOSYSTEM DEVELOPMENT

This project was recently funded (April 2008) by the NSF Ecological biology cluster and seeks to better understand the depth of bacterial community diversity in soils, and whether soil microbial community composition and structural dynamics follow a successional trajectory during ecosystem development, perhaps similar to the patterns of succession often observed in aboveground vegetative systems. Preliminary work conducted on the Altamaha dunes in southeast Georgia indicate that microbial communities do develop and increase in diversity during the aggrading stages of soil and ecosystem maturity. In collaboration with the University of Georgia, we will be using state of the art pyrosequencing techniques to characterize >200,000 16S rDNA sequences derived from soil bacteria along soil development gradients in the dunes of Northwest MI and southeast GA.  Shankar Shanmugam, a graduate student, is working on this project. 

IMPACT OF AGRICULTURAL LAND MANAGEMENT PRACTICES ON THE COMPOSITION OF THE SOIL BACTERIAL COMMUNITY

The research project funded by the USDA-NRI-CGP seeks to determine how agricultural practices change the bacterial community in soil. While this research will provide fundamental insights into the impacts of management practices on the soil prokaryotes, it will also have broad impacts in many other areas, such as the 1. Identification of bacteria abundant in agricultural soil,  2. Biogeographic diversity of soil prokaryotes, and the 3. Mining of biodiversity. Soil prokaryotes are extraordinarily diverse, and soil may represent a large fraction of the prokaryotic diversity of earth. Knowledge of the extent and distribution of this diversity will greatly facilitate its biotechnological exploitation. In this project, the bacterial (16S rDNA) and total microbial (PLFA) community structure  is being studied from soils under different management systems at the J. Phil Campbell, Sr., Natural Resource Center near Watkinsville, Georgia, the Konza Prairie Biological Station in Kansas, and the Kellogg Biological Station in Michigan.

PROTEOMICS OF NATURAL AND COMPLEX SOIL MICROBIAL COMMUNITIES

The utilization of the protein sequences to understand the functional capacities of microorganisms and plants has had great success over the last several years. However, only a few studies have attempted to better characterize the proteome of the complete soil microbial communities in situ.  Because of their huge phylogenetic diversity, we expect that soil microbial communities will be composed of equally diverse and complex pools of proteins. The discovery of these diverse pools could help to shed light on the types of microorganisms in soils, their functions, and aid in the capacity to isolate more microbial types for biotechnological applications.  Erin Bassford, a Research Associate, is evaluating different methods to extract protein from soil in order to identify proteins using MS/MS technology.  

WATER STRESS RESPONSES OF SOIL MICROORGANISMS

For several years we have been studying the dynamic response of soil microbial communities to the stress of drying and re-wetting of soil. During this time and into the future we are seeking to better characterize the chemical composition of putative microbial derived substrates that result upon the re-wetting of a dry soil. This work is in collaboration with the USDA Natural Products Laboratory (Oxford, MS) and the State Chemical Laboratory of Mississippi (MSU).  Madhavi Kakumanu, a graduate student, is working on an experiment that seeks to find the best ways to characterize and determine the nature of the microbial community response to water stress along a water stress gradient.

COLONIZATION OF GRASS STRAW RESIDUES BY BACTERIAL COMMUNITIES DURING DECOMPOSITION

We will assess the colonization of rice (Oryza sativa) and switchgrass (Panicum virgatum) straw residues by the microbial and bacterial communities throughout a 4-month incubation in two different soils. We are seeking to understand the extent of the effect that soil and residue type have on the type of colonizing microorganisms. Among other questions, we expect that the two soils will strongly influence the type of colonizing community, perhaps indicating that functional redundancy among diverse communities results in similar function (decomposition of residues). This research is being conducted by Maia Mula, a graduate student.