Phosphonoacetic acid utilization by fungal isolates: occurrence and properties of a phosphonoacetate hydrolase in some Penicillia

Among a collection of 18 fungal strains representing eight genera, only two strains (Penicillium oxalicum and P. minioluteum) were capable of growth on phosphonoacetic acid as sole phosphorous source. Enrichment liquid cultures in minimal medium with the compound as the only P-source selected four isolates, that were also identified as Penicillium spp. Phosphonoacetate metabolism did not lead to extracellular release of inorganic phosphate. In all cases phosphonoacetate hydrolase activity was detected in partially purified extracts, and a protein of the expected molecular mass reacted with polyclonal antibodies raised against the enzyme from P. oxalicum. There was no relation between phosphonoacetate hydrolase specific activity and growth rate or yield. Phosphonoacetic acid was the inducer of the hydrolase, independently of the concurrent availability of inorganic phosphate. Notwithstanding this, the utilization of the phosphonate was significantly inhibited in the presence of phosphate, suggesting an interference of the latter with phosphonoacetic acid uptake.