Herbicides tolerance in Pseudomonas veronii

The use of herbicides has become indispensable in agriculture to control weeds and increase crop yields. However, overuse and inappropriate application of these products affect the ecosystem, leading to soil and water pollution and generating environmental concern. Herbicides should be toxic only to target organisms, but most are non-specific and may affect microbiomes due their toxicity and persistence in the environment. Bacteria are constantly being subjected to environmental changes, so they have developed systems that allow adaptation to environmental fluctuations. Bacteria- bacteria interactions are coordinated through intercellular communication systems known as quorum sensing, which can regulate a number of activities, such as expression of the virulence factor, bioluminescence, biofilm formation, etc., and is performed through production of chemical signaling molecules, the auto-inducers. The objective of this work was to evaluate the tolerance capacity of Pseudomonas veronii to different herbicides. The bacterial strain was isolated from water storage tanks used in the washing of herbicide containers at Fazenda Escola Capão da Onça, UEPG. The herbicides saflufenacil, sulfentrazone, glyphosate, 2,4-D and dicamba were used as selective agents. The strain was tested for tolerance to herbicides in microplates containing Luria Broth (LB) and Mineral Glucose Medium (MM), at the field doses concentrations of 1x and 10x of the herbicides, calculated from the indicated in the product labels. The growth rates of P. veronii presented tolerance rates in LB treatments with saflufenacil, but not with sulfentrazone, although these two herbicides presented similar chemical structures. In the treatments in LB with dicamba the strain grew, but not with 2,4-D. These herbicides have similar chemical structures too, and also like the former two herbicides, inducing different responses by the bacterium. The strain presented growth only with dicamba and 2,4-D in MM. Glyphosate was toxic to the strain in MM, as no growth was observed in this medium. Nevertheless, in LB this strain presented growth rates only up to the concentration of 10x. These data indicate a nutritional effect on the bacterium tolerance capacity and a possible use of herbicides as source of nutrients. The role of quorum sensing in the modulation of adaptive and differentiated responses to these herbicides under stress conditions are being tested in liquid chromatography and mass spectrometry.