Large Sulfur Bacteria and the Formation of Phosphorite

Abstract

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 (</=300 micromolar) and massive phosphorite accumulations (>/=50 grams of phosphorus per kilogram). Laboratory experiments revealed that under anoxic conditions, Thiomargarita released enough phosphate to account for the precipitation of hydroxyapatite observed in the environment.

Physiology and behaviour of marine Thioploca

“…These include nitrate and sulphur accumulation, mixotrophic assimilation of CO 2 and organic substrates such as acetate, and the ability to perform dissimilatory nitrate reduction to ammonium (DNRA; Fossing et al, 1995;McHatton et al, 1996;Otte et al, 1999;Schulz et al,1999;Sayama et al, 2005). Recent genomic studies of Beggiatoa and physiological studies of Thiomargarita (Schulz and de Beer 2002;Schulz and Schulz 2005;Mussman et al, 2007) indicate that the giant sulphur bacteria have diverse pathways of energy metabolism, which includes both DNRA and denitrification, oxygen respiration and an auxiliary energy reservoir of polyphosphate. The question arises whether these properties also apply to Thioploca.…”

Diversity of Freshwater Thioploca Species and Their Specific Association with Filamentous Bacteria of the Phylum Chloroflexi

“…For intracellular polyphosphate staining, intact Thioploca filaments were immersed in toluidine blue solution as described previously [39]. To detect glycogen and other polyglucose storage molecules, Lugol staining was also carried out [39].…”

“…They can accumulate large amounts of nitrate and elemental sulfur, and use them for respiration. In addition to the elements mentioned above, nitrate-storing sulfur oxidizers may influence the phosphorus cycle, as it has been shown that some of them accumulate phosphorus as polyphosphate in their cells [4,39]. The intracellular accumulation of polyphosphate to overcome physical and chemical stress is widespread among microorganisms [5,12,23,28], although absence of polyphosphate granules in cells of Thioploca has been repeatedly reported [14,15,16,22].…”

Petrography and the REE-composition of apatite in the Paleoproterozoic Pilgujärvi Sedimentary Formation, Pechenga Greenstone Belt, Russia

“…Arning et al, 2009) in continental shelf environments where upwelling of nutrient-rich, deep-ocean water facilitates high biological production (Föllmi, 1996). Fluctuating anoxic-suboxic redox conditions and redox-dependent microbial processes within the sediment pore space leads to elevated phosphate concentrations resulting in apatite precipitation (Schulz and Schulz, 2005).…”

“…Fe/Mn redox cycling and mineralization of organic matter by bacterial sulfate reduction and/or emergence of habitats for sulfur-bacteria (Krajewski et al, 1994, Schulz and Schulz, 2005, Nelson et al, 2010and Lepland et al, 2014, the phosphate concentration and precipitation during the Paleoproterozoic would have required establishment of suboxic or oxic seawater conditions and, most importantly, development of fluctuating redox conditions in sediments that is crucial for concentrating interstitial phosphate.…”