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.
Highlights
The application of xenobiotic compounds generates environmental concern by the potential of the unwanted side effects, as large amounts of substances are released into the environment
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
Five bacterial strains were isolated from different untreated soils of Algeria; these isolates have shown an ability to grow in a culture medium in the presence of the herbicide glyphosate as sole source of carbon or phosphorus
Summary
The application of xenobiotic compounds generates environmental concern by the potential of the unwanted side effects, as large amounts of substances are released into the environment. The degradation of xenobiotic compounds is an important indicator for healthy ecosystems. Soil microorganisms can carry out pesticide degradation and can use the xenobiotic as a source of carbon, energy and other nutrients to promote microbial growth (Durkin, 2003). Despite its extensive use in Algeria, detailed informations on glyphosate degrading-microorganisms are lacking. Glyphosate (N-phosphonomethylglycine) is the most commonly used herbicide worldwide (Franz et al, 1997); it is a broad-spectrum, post-emergence, non-selective herbicide, that inhibits the enzyme 5-enolpyruvylshikimic acid-3-phosphate synthase (EPSPS), blocking the synthesis of essential aromatic amino acids (Duke et al, 2003). The importance of glyphosate degrading-bacteria has been magnified by the biotechnology application. The bacterial genes encoding for glyphosateresistant EPSP synthase were cloned, endowed with
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