Agriculture uses many food production chains, and herbicides participate in this process by eliminating weeds through different biochemical strategies. However, herbicides can affect non-target organisms such as bacteria, which can suffer damage if there is no efficient control of reactive oxygen species. It is not clear, according to the literature, whether the efficiency of this control needs to be selected by the presence of xenobiotics. Thus, the Pseudomonas sp. CMA 6.9 strain, collected from biofilms in an herbicide packaging washing tank, was selected for its tolerance to pesticides and analyzed for activities of different antioxidative enzymes against the herbicides Boral®, absent at the isolation site, and Heat®, present at the site; both herbicides have the same mode of action, the inhibition of the enzyme protoporphyrinogen oxidase. The strain showed tolerance to both herbicides in doses up to 45 times than those applied in agriculture. The toxicity of these herbicides, which is greater for Boral®, was assessed by means of oxidative stress indicators, growth kinetics, viability, and amounts of peroxide and malondialdehyde. However, the studied strain showed two characteristic antioxidant response systems for each herbicide: glutathione-s-transferase acting to control malondialdehyde in treatments with Boral®; and catalase, ascorbate peroxidase, and guaiacol peroxidase in the control of peroxide induced by Heat®. It is possible that this modulation of the activity of different enzymes independent of previous selection characterizes a system of metabolic plasticity that may be more general in the adaptation of microorganisms in soil and water environments subjected to chemical contaminants. This is relevant to the impact of pesticides on the diversity and abundance of microbial species as well as a promising line of metabolic studies in microbial consortia for use in bioremediation.

Herbicides are widely used in agricultural practices for preventing the proliferation of weeds. Upon reaching soil and water, herbicides can harm nontarget organisms, such as bacteria, which need an efficient defense mechanism to tolerate stress induced by herbicides. 2,4-Dichlorophenoxyacetic acid (2,4-D) is a herbicide that exerts increased oxidative stress among bacterial communities. Bacterial isolates were obtained from the biofilm of tanks containing washing water from the packaging of different pesticides, including 2,4-D. The Pseudomonas sp. CMA-7.3 was selected because of its tolerance against 2,4-D toxicity, among several sensitive isolates from the biofilm collection. This study aimed to evaluate the antioxidative response system of the selected strain to 2,4-D. It was analyzed the activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase GPX enzymes, that are poorly known in the literature for bacterial systems. The Pseudomonas sp. CMA-7.3 presented an efficient response system in balancing the production of hydrogen peroxide, even at 25x the dose of 2,4-D used in agriculture. The antioxidative system was composed of Fe–SOD enzymes, less common than Mn–SOD in bacteria, and through the activities of KatA and KatB isoforms, working together with APX and GPX, having their activities coordinated possibly by quorum sensing molecules. The peroxide control is poorly documented for bacteria, and this work is unprecedented for Pseudomonas and 2,4-D. Not all bacteria harbor efficient response system to herbicides, therefore they could affect the diversity and functionality of microbiome in contaminated soils, thereby impacting agricultural production, environment sustainability and human health.

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Herbicides are widely used in agricultural practices for preventing the proliferation of weeds that compete with crops for survival. Upon reaching soil and water, herbicides can damage nontarget organisms, such as bacteria, which need an efficient defense mechanism to tolerate the stress induced by herbicides. 2,4-Dichlorophenoxyacetic acid (2,4-D) is a herbicide that exerts increased oxidative stress among bacterial communities that consequently witness an increased toxicity in their microenvironments. Bacterial isolates were obtained from the biofilm of water that was contaminated with 2,4-D. This biofilm originated from the tanks containing washing water from the packaging of different pesticides, including 2,4-D. Moreover, several isolates were sensitive to biofilm toxicity; however, they remained alive in the presence of 2,4-D. The Pseudomonas sp. CMA-7.3 was selected because of its tolerance against biofilm agrochemicals. Therefore, the objective of this study is to evaluate the antioxidative response system of the Pseudomonas sp. CMA-7.3. This study also analyzed poorly evaluated enzymes, such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase GPX, in the bacterial systems. The toxic effects of 2,4-D on bacteria were evaluated using mechanisms indicating oxidative stress, such as growth curve, cell viability, peroxide, and malondialdehyde. The Pseudomonas sp. CMA-7.3 was an efficient response system against the activity of antioxidant enzymes such as SOD, CAT, APX, and GPX in balancing the production of H 2 O 2 , even at high doses as 25x the field dose of the herbicide, thereby proving the toxicity of 2,4-D for this strain and showing the ability of the strain to tolerate 2,4-D. The adaptation of this microorganism to herbicide exposure is truly relevant for improving future metabolic studies on bacterial communities. The strain showed a great potential in the application and developmental prospects of a new product in the bioremediation process of environments contaminated by these herbicides.

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