Atrazine biodegradation in the lab and in the field: enzymatic activities and gene regulation

Abstract

SummaryAtrazine is an herbicide of the s‐triazine family that is used primarily as a nitrogen source by degrading microorganisms. While many catabolic pathways for xenobiotics are subjected to catabolic repression by preferential carbon sources, atrazine utilization is repressed in the presence of preferential nitrogen sources. This phenomenon appears to restrict atrazine elimination in nitrogen‐fertilized soils by indigenous organisms or in bioaugmentation approaches. The mechanisms of nitrogen control have been investigated in the model strain Pseudomonas sp. ADP. Expression of atzA, atzB ad atzC, involved in the conversion of atrazine in cyanuric acid, is constitutive. The atzDEF operon, encoding the enzymes responsible for cyanuric acid mineralization, is a target for general nitrogen control. Regulation of atzDEF involves a complex interplay between the global regulatory elements of general nitrogen control and the pathway‐specific LysR‐type regulator AtzR. In addition, indirect evidence suggests that atrazine transport may also be a target for nitrogen regulation in this strain. The knowledge about regulatory mechanisms may allow the design of rational bioremediation strategies such as biostimulation using carbon sources or the use of mutant strains impaired in the assimilation of nitrogen sources for bioaugmentation.

Ametryn removal by Metarhizium brunneum: Biodegradation pathway proposal and metabolic background revealed

“…Complete mineralization is the most favorable way of biodegradation; however, the vast majority of the xenobiotics biodegradation pathways (including triazines) end in the formation of by-products. Formation of ametryn metabolites during the experiments presented in this work is partially in agreement with the reactions of atrazine biodegradation, where the formation 2-hydroxyatrazine has been observed in many species (Atrazine Pathway Map, 2017; KEGG Atrazine degradation -Reference pathway, 2017; Govantes et al, 2009;Solomon et al, 2013;Abigail et al, 2013), while deethylation of ethanamine substituents seems to be characteristic for fungal strains and mammals (Chirnside et al, 2011;Pereira et al, 2013, Sciali et al, 2014. Figure 6.…”

Transcriptional Organization and Regulatory Elements of a Pseudomonas sp. Strain ADP Operon Encoding a LysR-Type Regulator and a Putative Solute Transport System

“…Although s-triazine transport by degrading strains has not been studied in detail, indirect evidence of an s-triazine transporter has been documented for several organisms (18,48,54), including Pseudomonas sp. strain ADP (15,22,38). Proximity to the cyanuric acid utilization atzDEF operation and coregulation by the general nitrogen control system and AtzR suggest that they may be involved in the transport of cyanuric acid.…”

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“…In bioremediation of groundwater study, atrazine is readily biodegraded under controlled conditions (Shapir et al, 2007). It was found that biodegrading capacity is inhibited in the presence of external nitrogen and carbon sources (Govantes et al, 2009). On the other study of Agrobacterium radiobactor strain J14a, the degradation rate of atrazine was enhanced in Sequential Batch Biofilm Reactor (SBBR) after the additional supply of carbon source (Protzman et al, 1999).…”