Microbial Observatories: Salt Marsh Microbes and Microbial Processes: Sulfur and Nitrogen

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9977897HobbieThis Microbial Observatory at the Plum Island Long Term Ecological Research (LTER) site in northeastern Massachusetts identifies microbes and microbial communities in the salt marsh and determines their role in controlling major ecosystem processes. The observatory project, staffed by scientists from the Marine Biological Laboratory (MBL), the Woods Hole Oceanographic Institution, and Northwestern University, adds knowledge of the microbes and their ecology to the LTER research on the effects of changing inorganic nutrient supply and the quality and quantity of organic matter on estuarine trophic structure. The LTER research gains detailed knowledge about the microbial communities underlying the processes and control parameters which it investigates; the Microbial Observatory uses LTER data to place microbial communities into the larger context of their physical and chemical environment. In the salt marsh sediments, nitrogen and sulfur cycles influence all of the salt marsh biogeochemical cycles while sulfate reduction dominates decomposition. Therefore, the Observatory Project focuses on the microbes involved with the nitrogen and sulfur cycle with special attention to nitrification and sulfate reduction. This focus is possible because these investigators bring a suite of tools for culturing, molecular detection, and identification of nitrifying and sulfate reducing bacteria. The Microbial Observatory carries out the following activities: 1. identifies the microbes and microbial communities by means of culture and sequencing techniques, 2. investigates the seasonal changes in the community structure with culture methods and with denaturing gradient gel electrophoresis (DGGE) of nucleic acids, 3. links functional genes and microbial populations responsible for specific processes with rRNA hybridization techniques, and 4. correlates the presence and activity of various populations with ecological measurements of major processes in the salt marsh. Molecular surveys using functional genes and rRNA hybridization techniques are correlated with LTER measures of sulfate reduction and the nitrogen cycle. Carbon sources are identified with techniques using the delta 13C of phospholipid fatty acids specific to bacteria. Salt marshes provide one of the best examples of a site where microbes build and shape an entire ecosystem. Cyanobacteria are the pioneer organisms in salt marshes; they initiate microbial mat communities on mudflats that prevent erosion, trap sediment particles, and elevate the surface of the sediments. When higher plants colonize the site, the microbes fix nitrogen, recycle organic matter and nutrients, oxidize sulfides, and provide food for higher trophic levels. Salt marshes continue to be important models for basic microbiological and biogeochemical research. These systems are easily accessible. Their high process rates, large and diverse populations of functionally distinct microbes, and steep chemical and microbial gradients allow scientists to understand how microbial interactions and chemical cycles work. For example, many of our insights into the process and microbiology of sulfate reduction in the marine environment have come from the study of salt marshes. The value of salt marshes in teaching and education is well established. Students of the Microbial Diversity Course at the MBL in Woods Hole, associated with this Microbial Observatory, use the salt marsh as a "Microbial Rainforest" for the isolation and identification of a wide diversity of microbes.