Sistemas de respostas adaptativas ao glifosato em populações bacterianas isoladas em água

Abstract

The use of herbicides has been commercially expanding and there is concern in understanding the adverse effects that these pesticides can cause in animals, plants and microorganisms. Mainly because these residues may remain in the environment for long periods. The aim of this study was to evaluate some enzymatic and structural mechanisms of tolerance against toxic agents in bacteria, and these could constitute a system of responses to adaptation to extreme environments. Pseudomonas fluorescens is a strain isolated from wash water fifty packaging agrochemicals and was characterized as tolerant to glyphosate herbicide. We evaluated some tolerance strategies involving antioxidative enzymes and changes in the permeability of the cytoplasmic membrane. The activities of the enzymes superoxide dismutase (SOD) and catalase (CAT) involved in antioxidative process were analyzed in non-denaturing gel, and stress indicators were assessed by cell viability malondealdeído rates (MDA) and Hydrogen Peroxide (H2O2). It used the mineral medium (MM) with different glyphosate concentrations, based on the concentration of the herbicide used and the field (MM without herbicide control, MM1, since the concentration camp, MM10, MM40 and MM50). The bacterial growth rates were lower in MM40 and MM50 concentrations in the early log phase compared with the control. When comparing rates of H2O2 control has a relatively low production early log phase increases, significant starting from the intermediate log, having the same effect on growth rate. Control MDA rates have correspondence with the H2O2 rates and possible levels of lipid peroxidation. In MM10 treatment was the highest MDA rate corresponding to the rate of H2O2. The Mn-SOD isoform had its activity at the beginning and end of the log in control, MM50 has not been determined no activity. CAT isoforms HPI in control, was observed in all stages of the log, with the peak in the middle of the log. In the presence of glyphosate both isoforms showed high activity in MM1 and MM10 treatments, but very low in MM40 and MM50, these isoforms were key against stress generated by glyphosate to the MM10 treatment. P. fluorescens strain showed to be tolerant in MM1 and MM10 at the beginning middle and end of the log phase, with high rate of activity of antioxidant enzymes SOD and CAT.