Physiological aspects of glyphosate degradation in Alcaligenes spec. strain GL.

Alcaligenes spec. strain GL (IMET 11314) is able to grow on glyphosate (N-[phosphonomethyl]glycine) and other phosphonates as sole source of phosphorus. Degradation of glyphosate to inorganic phosphate and sarcosine by this strain is subject to several regulatory principles. While uptake and dephosphonation of glyphosate are regulated by P starvation, the intensity of glyphosate degradation is also controlled by the cellular ability to utilize the C-skeleton derived from glyphosate. Depending on the external concentration of glyphosate, the liberated sarcosine is differentially metabolised. Utilization of the sarcosine moiety and complete incorporation of 3-[C]-label of glyphosate into cellular material occur only in cultures adapted to higher concentrations (5 mM) of the herbicide. At low concentrations of glyphosate (1 mM) only the P required by the growing cultures is utilized but not the sarcosine. Initially high rates of glyphosate uptake obtained after P-starvation decrease in the presence of low glyphosate concentrations. It is suggested that uptake and metabolism of glyphosate are connected with the expression of the sarcosine metabolizing capacity of the Alcaligenes cells. [ABSTRACT FROM AUTHOR]