Most probable number quantification of hypophosphite and phosphite oxidizing bacteria in natural aquatic and terrestrial environments

Concentrations of hypophosphite and phosphite oxidizing bacteria were found to be high, relative to bacterial concentrations growing on phosphate, in sediment and soil during winter and summer seasons from 12 common terrestrial and aquatic sites using a most probable number method. The percent of total culturable bacterial concentrations that could use these reduced phosphorus compounds as a sole source of phosphorus were as follows: hypophosphite, 7-100%; phosphite, 10-67%; aminoethylphosphonate, 34-270%. The average MPN/g (+/- SEM) was as follows: phosphate, 6.19 x 10(6) (+/- 2.40 x 10(6)); hypophosphite, 2.61 x 10(6) (+/- 1.35 x 10(6)) phosphite, 1.91 x 10(6) (+/- 1.02 x 10(6)); aminoethylphosphonate, 3.90 x 10(6) (+/- 1.95 x 10(6)). Relatively high concentrations of reduced phosphorus oxidizing bacteria were found in both pristine sites and sites with urban and agricultural disturbance. Concentrations of reduced phosphorus oxidizing bacteria in anoxic sediments and soil were equivalent. Our data indicate that reduced phosphorus oxidizing bacteria are abundant in the environment and provide strong evidence for the importance of bacterial P oxidation in nature.