The effect of heavy metals and other environmental conditions on the anaerobic phosphate metabolism of Acinetobacter johnsonii

A strain of Acinetobacter with potential for bioremediation of heavy metal- contaminated waters was isolated from a wastewater-treatment plant operatin g an enhanced biological phosphate removal process. NMR and extractive meth ods showed that polyphosphate accumulated aerobically was degraded under an aerobic conditions both in the presence and absence of cadmium or uranium ( 0.2-0.5 mM). NMR showed that free phosphate was formed at the expense of po lyphosphate, and an extractive technique indicated that this reaction could be stimulated by the presence of UO22+ under these conditions. Energy-disp ersive X-ray microanalysis demonstrated that only cadmium could enter the c ells, and co-localized with intra-cellular granules containing phosphate an d other divalent metals. The effects of other environmental parameters on t he anaerobic phosphate metabolism were also investigated. Between pH 5.5 an d 8.0, phosphate release increased with increasing ph. Between 4 degrees C and 37 degrees C, phosphate release increased with increasing temperature. The presence of nitrate at concentrations of 10 mM and above inhibited an o xic phosphate release, but supplying tungstate in the growth medium prior t o anoxic incubation reduced the production of active nitrate reductase and alleviated this effect.