Abstract
Burkholderia zhejiangensis CEIB S4-3 has the ability to degrade methyl parathion (MP) and its main hydrolysis byproduct p-nitrophenol (PNP). According to genomic data, several genes related with metabolism of MP and PNP were identified in this strain. However, the metabolic state of the strain during the MP degradation has not been evaluated. In the present study, we analyzed gene expression changes during MP hydrolysis and PNP degradation through a transcriptomic approach. The transcriptional analysis revealed differential changes in the expression of genes involved in important cellular processes, such as energy production and conversion, transcription, amino acid transport and metabolism, translation, ribosomal structure and biogenesis, among others. Transcriptomic data also exhibited the overexpression of both PNP-catabolic gene clusters (pnpABA′E1E2FDC and pnpE1E2FDC) present in the strain. We found and validated by quantitative reverse transcription polymerase chain reaction the expression of the methyl parathion degrading gene, as well as the genes responsible for PNP degradation contained in two clusters. This proves the MP degradation pathway by the strain tested in this work. The exposure to PNP activates, in the first instance, the expression of the transcriptional regulators multiple antibiotic resistance regulator and Isocitrate Lyase Regulator (IclR), which are important in the regulation of genes from aromatic compound catabolism, as well as the expression of genes that encode transporters, permeases, efflux pumps, and porins related to the resistance to multidrugs and other xenobiotics. In the presence of the pesticide, 997 differentially expressed genes grouped in 104 metabolic pathways were observed. This report is the first to describe the transcriptomic analysis of a strain of B. zhejiangensis during the biodegradation of PNP.
Highlights
Organophosphorus pesticides are one of the most commonly used groups of pesticides worldwide (Tiwari et al, 2018); they have been used extensively in agricultural and household pest control, mainly against insects (Pope, 1999)
Based on the observed release of PNP since the beginning of the assay, B. zhejiangensis CEIB S4-3 carried out a fast Methyl parathion (MP) hydrolysis
The MM + MP did not present hydrolysis of the pesticide because PNP was not generated, which suggested that the MP hydrolysis and the subsequent degradation of PNP is due only to the enzymatic activity of the strain of B. zhejiangensis CEIB S4-3 (Fig. 2)
Summary
Organophosphorus pesticides are one of the most commonly used groups of pesticides worldwide (Tiwari et al, 2018); they have been used extensively in agricultural and household pest control, mainly against insects (Pope, 1999) Their intensive use is often related to environmental pollution events in agricultural soils and the surrounding water (Diagne, Oturan & Oturan, 2007; Begum & Arundhati, 2016; Ahn et al, 2018; Tiwari et al, 2018). Methyl parathion (MP) is an organophosphate pesticide that is broadly used in agriculture (Moreno-Medina, Sánchez-Salinas & Ortiz-Hernández, 2014) and has been classified by the World Health Organization as an extremely hazardous compound (Azaroff, 1999; Diagne, Oturan & Oturan, 2007) This organophosphorus pesticide is susceptible to microbial degradation, through a process mediated by hydrolytic enzymes, which releases p-nitrophenol (PNP) as the main product (Wang et al, 2014). Different microorganisms have been reported to have the capability to hydrolyze MP (Zhao et al, 2014); the number of microorganisms with metabolic strategies for the biodegradation of both MP and PNP is still limited
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