A METHOD TO DETERMINE THE CONTRIBUTION OF BACTERIA TO PHOSPHATE-UPTAKE BY AEROBIC FRESH-WATER SEDIMENT

An extraction method to determine the contribution of bacterial proces ses to phosphate uptake of aerobic freshwater sediment was tested on F e hydroxyphosphate that was either synthesized or formed under in situ conditions and a pure culture of Acinetobacter 210A. A mild extractio n with H2SO4 solubilized the entire Fe hydroxyphosphate fraction but d id not extract bacterial phosphate. Phosphate uptake of randomly sampl ed surface layers of the sediment of Lake Loosdrecht was considerable, ranging from 11 to 138 mumol g-1 on a dry weight basis. The contribut ion of bacterial processes ranged from 12 to 32%. Addition of an easil y degradable substrate, such as acetate, to the sediment stimulated th e uptake of phosphate and augmented the biologically bound phosphate f raction. The results indicated that growing bacteria play a considerab le role in phosphate uptake by acrobic sediment.