Tolerance of Pseudomonas strain to the 2,4-D herbicide through a peroxidase system.

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.

Specific quorum sensing molecules are possibly associated with responses to herbicide toxicity in a Pseudomonas strain.

Pesticides contribute to pest control and increase agricultural production; however, they are toxic to non-target organisms, and they contaminate the environment. The exposure of bacteria to these substances can lead to the need for physiological and structural changes for survival, which can be determined by genes whose expression is regulated by quorum sensing (QS). However, it is not yet clear whether these processes can be induced by herbicides. Thus, the aim of this work was to determine whether there is a QS response system in the Pseudomonas fluorescens CMA55 strain that is modulated by herbicides. This strain was isolated from water storage tanks used for washing pesticide packaging and was tested against herbicides containing saflufenacil, glyphosate, sulfentrazone, 2,4-D, and dicamba as active molecules. Our results showed that in the presence of herbicides containing saflufenacil and glyphosate (the latter was not present at the bacterial isolation site) the strain had a profile of QS signaling molecules that may be involved in controlling the production of reactive oxygen species. Alternatively, the same strain, in the presence of sulfentrazone (it was not present at the bacterial isolation site), 2,4-D and dicamba-containing herbicides, presented another profile of molecules that may be involved in different stages of biofilm formation. These findings, as a first screening, suggest that this strain used strategies to activate antioxidant enzymes and biofilm production under the signaling of QS molecules to respond to herbicides, regardless of previous contact, representing a model of phenotypic plasticity for adaptation to agricultural environments that can be used in studies of herbicide bioremediation.

Herbicides Tolerance in a Pseudomonas Strain Is Associated With Metabolic Plasticity of Antioxidative Enzymes Regardless of Selection.

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.

Investigação dos efeitos do ácido 2, 4 diclorofenoxiacético sobre diferentes populações de neurônios mioentéricos do duodeno de ratos / Investigation of 2, 4 dichlorophenoxyacetic acid effects in different population of rat duodenum myenteric neurons / Investigación de los efectos del ácido 2, 4 diclorofenoxiacético sobre diferentes poblaciones de neuronas mioentéricas del duodeno de ratones

O herbicida mais usado, tanto em pequenas como em grandes propriedades, por isso mais amplamente estudado é o 2,4-D. Os estudos de toxicidade têm se concentrado sobre as alterações do sistema nervoso central, e por isto pouco se conhece sobre seus efeitos no sistema nervoso entérico. Com o objetivo de avaliar os efeitos do 2,4-D sobre os neurônios mioentéricos do duodeno de ratos foi fornecido durante 60 dias doses de 2,4-D na concentração de 5mg/kg de peso de corpóreo para ratosWistarde dois grupos experimentais (n=5). Os animais dos grupos controle permaneceram o mesmo período sem receber 2,4-D. Ao final do período experimental os animais foram mortos, os duodenos foram coletados e processados por meio das técnicas histoquímicas de NADH-diaforase e NADPH-diaforase. Os neurônios foram quantificados e os resultados foram analisados estatisticamente. A densidade dos neurônios NADHd diferiu estatisticamente (P?0,05) entre os grupos experimental e controle, sendo maior no grupo controle. Já os neurônios NADPHd foram encontrados em maior quantidade no grupo experimental. Estes resultados sugerem que o 2,4-D possui ação neurotóxica sobre os neurônios do plexo mioentérico, interferindo na densidade neuronal mioentérica, quando se compara diferentes populações destes neurônios...

The 2,4-D herbicide is the most widely used, both in small and in large properties. Therefore, it is also the one that is most broadly studied. Toxicity studies have been focused on changes in the central nervous system, and for this reason, little is known about its effect in the enteric nervous system. With the objective of measuring the effects of 2,4-D on the myenteric neurons in the duodenum of rats, doses of 2,4-D were supplied for 60 days at a concentration of 5mg/kg of body weight to Wistar rats divided into two different experimental groups (n=5). The animals in the control groups remained without 2,4-D doses for the same period. At the end of the experimental period, the animals were euthanized and their duodenum were collected and processed through NADH-diaphorase and NADPH-diaphorase histochemical techniques. The neurons were quantified and the results were statistically analyzed. The density of NADHd neurons differed statistically (P< 0,05) between the experimental and control groups, being higher in the control group. However, NADPHd neurons were found in a greater quantity in the experimental group. These results suggest that the 2,4-D has a neurotoxic action in the neurons from the myenteric plexus, interfering in the myenteric neuronal density, when different population of these neurons are compared...

El herbicida más utilizado, tanto en pequeñas como en grandes propiedades es el 2,4-D, por eso lo más estudiado. Los estudios de toxicidad se han centrado sobre las alteraciones del sistema nervioso central, y por lo tanto, poco se sabe sobre sus efectos en el sistema nervioso entérico. Con el objetivo de evaluar los efectos del 2,4-D sobre las neuronas mioentéricas del duodeno de ratas se ha administrado durante 60 días dosis de 2,4-D en la concentración de 5mg/kg de peso corporal para ratones Wistarde, dos grupos experimentales (n = 5). Los animales de los grupos control permanecieron el mismo período sin recibir el 2,4-D. Al final del periodo experimental los animales fueron sacrificados, los duodenos fueron recogidos y procesados a través de las técnicas de histoquímicas de NADH-diaforasa y NADPH-diaforasa. Las neuronas fueron cuantificadas y los resultados analizados estadísticamente. La densidad de las neuronas NADHd difirió estadísticamente (P?0,05) entre los grupos experimental y control, siendo mayor en el grupo control. Ya las neuronas NADPHd se encontraron en mayor cantidad en el grupo experimental. Estos resultados sugieren que el 2,4-D tiene una acción neurotóxica sobre las neuronas del plexo mioentérico, lo que interfiere en la densidad neuronal mioentérica al comparar diferentes poblaciones de estas neuronas...