Chapter 30.2, Problem 1MI

How is sulfur cycled between the anoxygenic photosynthetic microbes belonging to the genera Chlorobium and Chromatium, and anaerobic heterotrophic Desulfovibrio spp.?

Figure 30.5 The Winogradsky Column. Microorganisms and nutrients interact over a vertical gradient in these microcosms. Fermentation products and sulfide migrate up from the reduced lower zone, and oxygen penetrates from the surface. This creates conditions similar to those in a lake or salt marsh with nutrient-rich sediments. Light simulates the penetration of sunlight into the anoxic lower region, which stimulates photosynthetic microorganism growth.