Impact of sulfide-oxidizing bacteria on the phosphorus cycle in marine sediments

Studies with the marine Beggiatoa strain 35Flor revealed that intracellular polyphosphate is rapidly degraded and phosphate is released in response to a switch from oxic to anoxic conditions at high sulfide concentrations. This new mode of polyphosphate usage drastically increases phosphate concentrations in the surrounding medium and helps to explain high phosphate concentrations in organic rich sediments of coastal upwelling areas, which enhance the chance of apatite precipitation. The unusually large polyphosphate inclusions in Beggiatoa strain 35Flor represent a new type of storage compartment within the family Beggiatoaceae, aside of aqueous vacuoles that mostly contain nitrate. They are enclosed by a vacuolar membrane and contain cations such as calcium and magnesium. Furthermore, a Beggiatoa-induced decrease of uranium concentrations in natural seawater was observed.