Initial steps in the degradation of phosphinothricin (glufosinate) by soil bacteria

Abstract

Three hundred bacterial isolates from soil were tested for resistance against phosphinothricin [PPT; DL-homoalanin-4-yl(methyl)phosphinic acid], the active ingredient of the herbicide BASTA. Eight resistant bacterial strains and Escherichia coli were analyzed for PPT-transforming activities. At least three different enzymatic reactions could be detected in cell extracts. In six strains an acetyltransferase was active, synthesizing N-acetyl-PPT in the presence of PPT and acetyl coenzyme A. All strains could degrade PPT to its corresponding 2-oxoacid {2-oxo-4[(hydroxy)(methyl)phosphinoyl]butyric acid} by transamination. Rhodococcus sp., the only tested strain that was able to utilize PPT as a sole source of nitrogen, formed 2-oxo-4[(hydroxy)(methyl)phosphinoyl]butyric acid by oxidative deamination. This enzymatic activity was inducible by L-glutamic acid or PPT itself but not in the presence of NH4+. D-PTT transformation was not detectable in any of the investigated strains.