Growth-based Screening and Abiotic Tolerance Profiling of Glyphosate-Tolerant Bacteria Isolated from Pesticide-Exposed Agricultural Soils in Mostaganem, Algeria

Abstract

Glyphosate, which is called N-phosphonomethylglycine is the commonly used herbicide all over the world including in Algeria. It stays in the soil used for farming. Causes problems for the environment and for biotechnology. These problems are connected to soil pollution. What happens to a main breakdown product of glyphosate, which is called aminomethylphosphonic acid or AMPA. Native bacteria found in the soil that can use glyphosate as a source of carbon are very interesting because they might help clean up the soil. However we do not know enough about the types of these bacteria and how well they can handle glyphosate in the farming areas of Algeria and North Africa. Soil samples were taken in May 2023 from two farming areas, in Mostaganem, Algeria, These samples differ in herbicide history. One sample was treated times with glyphosate specifically with Roundup Ultra Plus. The other sample was treated with metribuzin and, with linuron. Researchers counted all microflora as well as those that are tolerant to glyphosate. They used dilution and plating techniques to do the counts. The cells were plated on Plate Count Agar. The cells were also plated on a salt medium that used glyphosate as the only carbon source. Thirty purified isolates were screened for growth at OD₆₆₀ over 120 hours, and effects of pH, temperature, NaCl concentration, glyphosate concentration, and glucose co-supplementation were evaluated. Glyphosate degrading microflora reached 6.632±0.01 Log CFU/g in treated soil, which’s ten times higher than in untreated soils. All thirty isolates were able to grow on glyphosate with peak growth happening between 48 and 120 hours. 80% Of the isolates preferred an alkaline pH environment. Eighteen isolates showed growth at 30°C. The bacteria could still grow in conditions with 5% NaCl. 5 g/L glyphosate. Glucose helped boost growth in every isolate. Twelve of the selected isolates belonged to families such as Pseudomonasaceae, Aeromonadaceae, Chromobacteriaceae, Rhizobiaceae and Vibrionaceae. These results show that Mostaganem agricultural soils contain a variety of bacterial species that can handle glyphosate. They also show tolerance to different environmental stresses. This makes them good candidates, for bioremediation studies. Before these strains can be used in real field situations it is necessary to confirm glyphosate removal using chemical methods. Molecular identification must also be done to know what species we are working with.