|Lab Contact Information|
|Lab Phone Number:||706.542.4692|
The University of Georgia
Department of Microbiology
541 Biological Sciences Building
Athens, GA 30602-2605, USA
|Information for Prof. Barny Whitman|
|Office Phone Number:||706.542.4219|
Prokaryotes are the dominant form of life on earth, representing an enormous biomass and number of individual cells. They are so diverse that it is misleading to give them a common name. They are really just what are left after the familiar plants, animals, fungi and protozoa are named. They are the engines that make the biosphere. They are the ancestors to all modern life, and their evolution established the central plan for the living cell.
Research in our laboratory uses an integrated approach to understand the nature of free-living prokaryotes. We believe that studying the ecology provides insight into the systematics provides insight into the physiology provides insight into the molecular biology. Likewise, the history or evolution of an organism provides insight into the modern organism. We have used these approaches to study the methane-producing archaeon Methanococcus, the marine alpha proteobacteria, and soil bacteria.
The methanogenic bacteria are strictly anaerobic autotrophs that obtain energy from the biosynthesis of methane gas. They catalyze the terminal step in the anaerobic decomposition of organic matter, and about 1.6% of the CO2 fixed worldwide by plants and algae is mineralized by the activity of these organisms. Atmospheric methane, a greenhouse gas whose concentration is rapidly increasing, is derived largely from this process. As autotrophs these prokaryotes are also unusual because they are commonly found closely associated with heterotrophic bacteria and protozoans.
Methanogens are archaea, and they are distantly related to both eukaryotes and the more common bacteria. Among the archaea, the methanogens are unique. They are the only cultivated archaea common in temperate environments of moderate temperature, neutral pH, and low salinity. Therefore, the properties of the methanogens can be easily compared with bacteria from identical habitats. This feature is important. It is reasonable to believe that properties of the methanogens that are shared by the bacteria may have been inherited by a common ancestor to all modern organisms. Thus, comparative physiology may allow us to deduce the properties of the common ancestor.
Our studies of marine bacteria have been performed in collaboration with a wonderful scientist, Mary Ann Moran, and her colleagues in the Dept. of Marine Sciences. Our current efforts seek to quantitatively describe the prokaryotic community at the Sapelo Island Microbial Observatory with ribosomal RNA gene libraries as well culture methods. The SIMO includes marshes dominated by the cord grass Spartina alterniflora as wells as estuaries and open seawater. It possesses strong spatial and biochemical gradients, including fresh to seawaters as well as aerobic and anaerobic sediments.
In addition to studies of the microbial communities, we are studying the physiology and biochemistry of Silicibacter pomeroyi, a marine alpha-Proteobacterium related to the Roseobacteria that was recently isolated from seawater. This organism is particularly interesting because it is capable of either mineralizing the common marine osmolyte dimethylsulfonium propionate (DMSP) to carbon dioxide or metabolizing it to dimethylsulfide (DMS). In oceans, DMS is a major source of atmospheric sulfur compounds, which in turn influence the formation of clouds. Nevertheless, the biochemical pathways and physiological controls for these processes are currently unknown. We are using proteomic, genetic and biochemical methods to identify the enzymes and genes involved in the pathway of DMSP degradation. Once in hand, these genes will be used as tools to study their expression in natural communities of marine bacteria.
In collaboration with biochemist and ecologist David C. Coleman of the Institute of Ecology, we are studying the prokaryotic communities of soil. Our current studies have used ribosomal RNA gene libraries to describe and compare the communities in agricultural soils under no tillage and conventional tillage management with adjacent forest soils. In another study, we are investigating the impact of various land management practices on the soil prokaryotic community and diversity. We have also studied the affect of earthworms on the microbial populations in soil and isolated and described some interesting soil bacteria.