The P in phosphonates has a stronger potential for electron sharing than the P in phosphates, based on the electronegativity difference between C and P (2.5–2.2) compared with O (3.5) and P in phosphates. Comprising 10–20% of the total dissolved P inventory in Florida environments, reduced P compounds could hence be a critical part of the phosphorus biogeochemical cycle, and in turn may impact global carbon cycling and methanogenesis.Īlthough inorganic phosphate and phosphate esters (P 5+) are viewed as the prevalent compounds in nature, phosphonates, with C−P bonds, are ubiquitous, comprising up to 25% of the dissolved organic P in some natural samples ( 2). Phosphine is generated at a quantity consistent with thermodynamic equilibrium established by the disproportionation reaction of reduced P species. If the quantity of reduced P observed in the water samples from Florida studied here is broadly characteristic of similar environments on the global scale, it accounts well for the concentration of atmospheric phosphine and provides a rationale for the ubiquity of phosphite utilization genes in nature. Here we show that between 10% and 20% of dissolved P bears a redox state of less than +5 in water samples from central Florida, on average, with some samples bearing almost as much reduced P as phosphate. Reduced P compounds have been considered to be rare however, the microbial ability to use reduced P compounds as sole P sources is ubiquitous. Reduced oxidation state P compounds include the phosphonates, characterized by C−P bonds, which bear up to 25% of total organic dissolved phosphorus.
Exceptions to pentavalent P include phosphine-PH 3-a trace atmospheric gas, and phosphite and hypophosphite, P anions that have been detected recently in lightning strikes, eutrophic lakes, geothermal springs, and termite hindguts.
The element phosphorus (P) controls growth in many ecosystems as the limiting nutrient, where it is broadly considered to reside as pentavalent P in phosphate minerals and organic esters.
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