PHOSPHATE AND SOIL BINDING - FACTORS LIMITING BACTERIAL-DEGRADATION OF IONIC PHOSPHORUS-CONTAINING PESTICIDE METABOLITES

Soils that had a high binding capacity for inorganic orthophosphate (Pi) had reduced capacities to bind ionic alkyl P compounds. Only ionic methylphosphonate (MPn) and ionic phenylphosphonate exhibited moderate binding. Pseudomonas testosteroni used either MPn or Pi as a sole P source and exhibited diauxic utilization of MPn and Pi. The utilization of MPn was suppressed in the presence of Pi. This suppression was abolished by a Pi-binding soil. The soil did not have a significant effect on the maximum rate of degradation of either MPn or the poorly bound ionic O-isopropul methylphosphonate, whereas the amount of MPn (but not the amount of O-isopropyl methylphosphonate) metabolized was reduced in the presence of soil.