Metabolism of glyphosate in an Arthrobacter sp. GLP‐1

Abstract

The metabolism of glyphosate [N‐(phosphonomethyl)glycine] in a bacterium tentatively identified as an Arthrobacter sp., capable of growth on this herbicide as its sole phosphorus source, has been investigated using solid‐state NMR techniques as well as radiotracer analysis. The pathway involves the conversion of glyphosate to glycine, a C1 unit and phosphate. The phosphonomethyl carbon is specifically incorporated into the amino acids serine, cysteine, methionine, and histidine, as well as into purine bases and thymine, indicating the involvement of tetrahydrofolate in single‐carbon transfer reactions. Glycine derived from glyphosate is utilized in purine and protein biosynthesis. This pathway for glyphosate degradation in a gram‐positive bacterium is similar to that previously reported for Pseudomonas sp. PG2982 [Jacob et al. (1985) J. Biol. Chem. 260, 5899–5905] and is distinct from that reported for soil metabolism of glyphosate where aminomethylphosphonic acid has been shown to be a major metabolite. Preliminary evidence is presented which indicates that the conversion of glyphosate to glycine and the C1 unit involves the intermediate formation of sarcosine. Thus, the primary event in glyphosate degradation by Arthrobacter sp. GLP‐1 is the cleavage of its C‐P bound. This report constitutes the first demonstration of the metabolism of glyphosate in a gram‐positive bacterium.

Respiração microbiana do solo sob doses de glyphosate e de imazapyr

“…Heinonen-Tanski (1989), Wardle & Parkinson (1990) e Wardle et al (1994) observaram que essa degradação está estreitamente relacionada à taxa de CO2 liberada do solo. A quebra da ligação C  P da molécula é apresentada como a primeira etapa desse processo (Kishore & Jacob, 1987;Pipke et al, 1987;Liu et al, 1991;Dick & Quinn, 1995), não havendo, entretanto, evidências de sua completa mineralização. Torstensson & Aamisepp (1977) constataram que o glyphosate não era diretamente utilizado como fonte de energia para a população microbiana, sendo apenas co-metabilizado.…”

Microbial metabolism of sulfurand phosphorus-containing xenobiotics

“…Glyphosate transport in Arthrobacter sp. GLP-1, for example, is also inhibited by phosphate [73]. Uptake of glyphosate into the cell is subject to both inhibition and repression by phosphate in this species [73], and phosphate starvation also leads to derepression 202 of glyphosate transport in Pseudomonas sp.…”

“…PG2982 [29]. The sarcosine formed has been shown by 13C/~SN-NMR studies to be further degraded to glycine and a C ~-unit, which is incorporated into purines and the amino acids serine, cysteine, methionine and histidine [26]. Alternatively, glyphosate may first be converted to aminomethylphosphonic acid (AMPA) by loss of a C2-unit, and this compound is then dephosphonylated (e.g.…”

“…Despite extensive efforts to stabilize them [23,26,28,31,32], C-P lyase activity measured as alkane release from alkanephosphonates has never been observed in cellfree extracts. It has generally been assumed that the mechanisms involved in cleavage of the various organophosphonates are similar, although recent evidence shows that, in Arthrobacter sp.…”

“…PG2982 [23]), an Alcaligenes isolate [24], Bacillus megaterium strain 2BLW [22], Arthrobacter sp. GLP-1 [26], four different Rhizobium species [27] and three Agrobacterium species [27,28] Glyphosate is degraded in bacteria by two main pathways, both of which lead to breaking of the carbon-phosphorus bond. In the first of these, initial cleavage of the carbon-phosphorus bond yields the reduced product N-methylglycine (sarcosine).…”