Phosphonate utilization by bacteria in the presence of alternative phosphorus sources

Batch and continuous culture experiments were carried out to investigate the effect of orthophosphate and p-nitrophenylphosphate on the utilization of various phosphonates as a P source by bacteria. Detailed tests with methylphosphonate as a model phosphonate and the phosphonate-degrading Pseudomonas paucimobilis strain MMM101a revealed that, in contrast with the majority of literature data, the phosphates did not suppress phosphonate utilization. Under conditions of P stress, strain MMM101a simultaneously took up both P-sources, with a preference for the phosphate-P. Study of the kinetic parameters for strain MMM101a, growing on the different P sources revealed similar, rather low, maximum growth rates (ca. 0.15 h-1). However, the affinity for orthophosphate (Ks:0.17 microM), was more than two orders of magnitude higher than for methylphosphonate (Ks: 66 microM), which might account for the preferential uptake of orthophosphate. Cellular phosphorus yields in continuous cultures varied considerably with the conditions applied. The results suggest that phosphonate degradation can occur also in environments with substantial backgrounds of phosphate.