Moléculas sinalizadoras de quorum sensing como respostas à toxicidade de herbicidas em Enterobacter sp.

Abstract

With the increase in the human population, agriculture needs to increase its productivity by at least 50% to meet this demand. A part of this production is lost to weeds, which makes the use of pesticides necessary. Consequently, contamination of the environment and selective pressure on environmental microbiomes occurs, which can alter biogeochemical cycles of which they are part. Microorganisms adapt to toxic conditions by developing strategies such as the production of exopolysaccharides (EPS) and biofilm formation, which allow the formation of a protective barrier to antimicrobials and biocides. The biofilm is modulated by cell-cell communication, known as quorum sensing (QS), which coordinates collective behaviors in bacterial communities and elicits stress responses through self-inducing molecules. The objective of this work was to evaluate a possible association between QS signaling molecules and response systems, composed of antioxidant enzymes to the herbicides Heat and Roundup. The bacterium Enterobacter sp. CMA55A, isolated from pesticide packaging washing tanks, in relation to tolerance to Heat and Roundup herbicides, present and absent at the isolation site, respectively. QS signaling molecules were extracted and analyzed using liquid chromatography coupled to mass spectrometry. In the presence of both herbicides, molecules C6-HSL, C7-HSL and C8-HSL were generated. These molecules act mainly on biofilm maturation, biofilm formation and protection against oxidative stress, respectively. There are reports in the literature on the relationship between QS signaling molecules and EPS production, and for the Enterobacter sp. CMA55A, production was observed for both herbicides and in the control, possibly by an antioxidant system modulated by QS, as a strategy to survive different environmental conditions, including the presence of herbicides. The C6-HSL and C8-HSL molecules were produced in control and 1x, while the C7-HSL molecule was produced in 10x, 40x and 50x. This may indicate that C7-HSL is more related to the response system to higher concentrations of herbicides, even though this condition is not normally found in agricultural soils. It is possible that the Enterobacter sp. CMA55A has responses that do not depend on previous selection, as it produced the same equivalent QS molecules at the same concentrations of the two herbicides. Thus, it is suggested that the microorganism has phenotypic plasticity to be able to adapt to similar stress conditions, even if originated by different substances. The results of this work can serve as a screening for research on the response of bacteria to contaminated environments, and possible uses in bioremediation by consortia controlled by QS signaling molecules.