In salt marsh ecosystems, living Sporobolus roots produce carbon compounds that feed sulfate reducing bacteria in the sediment around them (i.e. in the "rhizosphere"). As they respire, those bacteria transform sulfate from seawater into sulfide, which can build up to concentrations toxic for the plants. That sulfide is easily detected by our noses in salt marshes; it's the "rotten egg" smell.  

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Roots are not doomed to be poisoned by sulfide, however. There are many other types of microbes living in the sediment around the roots, and among them are sulfur oxidizing bacteria. They can use the sulfide as an energy source, and transform it back to sulfate, detoxifying the environment for the root. These sulfur oxidizing bacteria contribute to tremendous salt marsh productivity through their own growth and by maintaining healthy environmental conditions for Sporobolus.

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The symbiotic relationship among Sporobolus roots, and the sulfate reducing and sulfur oxidizing microbes around them in sediment, supports an ecosystem-scale production, recycling and detoxification system--a coastal hotbed of microbe-catalyzed sulfur cycling and healthy plant growth. We are developing tools to study this symbiosis.