Large sulfur bacteria and the formation of phosphorite.

Phosphorite deposits in marine sediments are a long-term sink for an essential nutrient, phosphorus. Here we show that apatite abundance in sediments on the Namibian shelf correlates with the abundance and activity of the giant sulfur bacterium Thiomargarita namibiensis, which suggests that sulfur bacteria drive phosphogenesis. Sediments populated by Thiomargarita showed sharp peaks of pore water phosphate (/=50 grams of phosphorus per kilogram).

Phylogeny and distribution of nitrate-storing Beggiatoa spp. in coastal marine sediments.

Filamentous sulphide-oxidizing Beggiatoa spp. often occur in large numbers in the coastal seabed without forming visible mats on the sediment surface. We studied the diversity, population structure and the nitrate-storing capability of such bacteria in the Danish Limfjorden and the German Wadden Sea.

Uptake rates of oxygen and sulfide measured with individual Thiomargarita namibiensis cells by using microelectrodes.

Gradients of oxygen and sulfide measured towards individual cells of the large nitrate-storing sulfur bacterium Thiomargarita namibiensis showed that in addition to nitrate oxygen is used for oxidation of sulfide. Stable gradients around the cells were found only if acetate was added to the medium at low concentrations.