DIFFERENCES IN POLYPHOSPHATE ACCUMULATION AND PHOSPHATE ADSORPTION BY ACINETOBACTER-ISOLATES FROM WASTE-WATER PRODUCING POLYPHOSPHATE - AMP PHOSPHOTRANSFERASE

Ten isolates of Acinetobacter spp, obtained from sewage and showing high activities of polyphosphate: AMP phosphotransferase [ranging from 10 to 57 nmol min-1 (mg protein-1)] were studied for their differences in polyphosphate accumulation. Using electron microscopy, differences in numbers and sizes of the stored granules for the different strains were observed. These granules could be unambiguously identified as polyphosphate granules by electron spectroscopic imaging (ESI). Size and numbers of these granules found in different strains correlated with the intensity of different bands obtained from fractionated polyphosphates by polyacrylamide gel-electrophoresis (PAGE). Two different fractions, both consisting of high molecular weight polyphosphates (equivalent chain length), were obtained. Their distribution was strain specific. By electron microscopy and the ESI technique it could be further shown that all strains produced extracellular polymers (ECP). For one strain, a considerable phosphate adsorption at these ECP was observed. These data indicate that even in pure culture studies, phosphate adsorption must be considered in addition to the phosphate metabolism of specialized organisms for a sufficient explanation of the excess "biological" phosphate removal. For the much more complex situation in sewage treatment plants it is indispensable to consider various biological and chemical mechanisms for a sufficient explanation of "biological phosphate removal".