Abstract

Glyphosate (N-phosphonomethylglycine) is the most commonly used herbicide worldwide. Due to the concern regarding its toxicity for non-targeted species in soil, finding glyphosate-degrading microorganisms in soil is of interest. The success of this will depend on isolating bacteria with the ability to grow in presence of glyphosate. Five bacterial strains were isolated from different untreated soils of Algeria, the strains were able to grow in a medium containing glyphosate as sole carbon or phosphorus source by enrichment cultures of these soils. Based on 16S rRNA gene sequence analysis, MALDI-TOF MS and biochemical properties, the best strain amongst them (Arph1) was identified as Pseudomonas putida. This isolate showed the highest growth level in the presence of glyphosate as sole phosphorus source. Arph1 was therefore used for further studies for optimization of cultivation conditions for an efficient glyphosate use. The best result of growth was on 1 g/L of glyphosate in minimal medium supplemented with glutamate with initial pH 9.0 at 30°C at 150 rpm within 168 h. Microbial growth during the study was monitored by measuring the optical density at 620 nm. Arph1 was able to tolerate up to 9 g/L of glyphosate. These results show that the bacterial strain may possess potential to be used in bioremediation of glyphosate-contaminated environments.

Key words: Soil pollution, glyphosate-degrading bacteria, Pseudomonas putida, optimization, cultivation conditions.