Mechanisms of Tolerance and High Degradation Capacity of the Herbicide Mesotrione by Escherichia coli Strain DH5-α

Abstract

The intensive use of agrochemicals has played an important role in increasing agricultural production. One of the impacts of agrochemical use has been changes in population structure of soil microbiota. The aim of this work was to analyze the adaptive strategies that bacteria use to overcome oxidative stress caused by mesotrione, which inhibits 4-hydroxyphenylpyruvate dioxygenase. We also examined antioxidative stress systems, saturation changes of lipid membranes, and the capacity of bacteria to degrade mesotrione. Escherichia coli DH5-á was chosen as a non-environmental strain, which is already a model bacterium for studying metabolism and adaptation. The results showed that this bacterium was able to tolerate high doses of the herbicide (10× field rate), and completely degraded mesotrione after 3 h of exposure, as determined by a High Performance Liquid Chromatography. Growth rates in the presence of mesotrione were lower than in the control, prior to the period of degradation, showing toxic effects of this herbicide on bacterial cells. Changes in the saturation of the membrane lipids reduced the damage caused by reactive oxygen species and possibly hindered the entry of xenobiotics in the cell, while activating glutathione-S-transferase enzyme in the antioxidant system and in the metabolizing process of the herbicide. Considering that E. coli DH5-α is a non-environmental strain and it had no previous contact with mesotrione, the defense system found in this strain could be considered non-specific. This bacterium system response may be a general adaptation mechanism by which bacterial strains resist to damage from the presence of herbicides in agricultural soils.

How the edaphic Bacillus megaterium strain Mes11 adapts its metabolism to the herbicide mesotrione pressure

“…In Bacillus, UDP-glucose has a central role as a metabolite for the synthesis of cell wall envelope polymers (Lazarevic et al, 2005;Grundling and Schneewind, 2007). However, when exposed to mesotrione, the a-phosphoglucomutase is under-expressed (PgcA; Table 1; spot 31), suggesting that the strain Mes11 has an altered membrane glycolipid synthesis as recently observed for Escherichia coli DH5a strain exposed to mesotrione (Olchanheski et al, 2014).…”

“…Mesotrione, chemically derived from a natural phytotoxin produced by the bottlebrush plant Callistemon citrinus (Mitchell et al, 2001), was developed to minimize adverse effects on the environment. Since mesotrione was marketed in 2003, few microorganisms have been reported to catabolize it (Durand et al, 2006;Batisson et al, 2009;Pileggi et al, 2012;Olchanheski et al, 2014). The detailed biodegradative pathway of mesotrione was only established with some of these microorganisms (Durand et al, 2010;Pileggi et al, 2012).…”

“…Thus, the members of this genus could fulfill a crucial role in mesotrione degradation in the natural environment. However, very scarce information exists on overall physiological response of bacteria exposed to applications of mesotrione and on microbial catabolic genes and enzymes involved in mesotrione degradation (Olchanheski et al, 2014).…”

Mesotrione Herbicide: Efficiency, Effects, and Fate in the Environment after 15 Years of Agricultural Use

“…Escherichia coli DH5‐α can withstand high doses of mesotrione (0.4 mM, corresponding to 10× field rate), and completely degrade the herbicide within 3 h of exposure . From the point of view of this study, and considering that E. coli DH5‐α is not an environmental bacterium, the defense system observed in this strain could be considered as non‐specific knowing that it had no previous contact with mesotrione.…”

Redox imbalance caused by pesticides: a review of OPENTOX-related research

“…A toxicity study of sulcotrione (90) showed up-regulation of the genes inducing ROS and antioxidant enzymes in the fava bean cells (Vicia faba), followed by increased lipid peroxidation. Some pathogens, in turn, such as E. coli DH5-α (91) and Pantoea ananatis (92), showed resistance to oxidative stress caused by mesotrione, while human liver cancer Hepg2 cells were only mildly affected by tembotrione (93).…”