Further Insights into the Architecture of the PN Promoter That Controls the Expression of the bzd Genes in Azoarcus

Durante-Rodríguez Durante-Rodríguez,Gutiérrez-Del-Arroyo Gutiérrez-Del-Arroyo,Carmona Carmona,Vélez Vélez,Díaz Díaz

doi:10.3390/genes10070489

Durante-Rodríguez Durante-Rodríguez, Gutiérrez-Del-Arroyo Gutiérrez-Del-Arroyo + Show 3 more

Open Access

https://doi.org/10.3390/genes10070489

Copy DOI

Abstract

The anaerobic degradation of benzoate in bacteria involves the benzoyl-CoA central pathway. Azoarcus/Aromatoleum strains are a major group of anaerobic benzoate degraders, and the transcriptional regulation of the bzd genes was extensively studied in Azoarcus sp. CIB. In this work, we show that the bzdR regulatory gene and the PN promoter can also be identified upstream of the catabolic bzd operon in all benzoate-degrader Azoarcus/Aromatoleum strains whose genome sequences are currently available. All the PN promoters from Azoarcus/Aromatoleum strains described here show a conserved architecture including three operator regions (ORs), i.e., OR1 to OR3, for binding to the BzdR transcriptional repressor. Here, we demonstrate that, whereas OR1 is sufficient for the BzdR-mediated repression of the PN promoter, the presence of OR2 and OR3 is required for de-repression promoted by the benzoyl-CoA inducer molecule. Our results reveal that BzdR binds to the PN promoter in the form of four dimers, two of them binding to OR1. The BzdR/PN complex formed induces a DNA loop that wraps around the BzdR dimers and generates a superstructure that was observed by atomic force microscopy. This work provides further insights into the existence of a conserved BzdR-dependent mechanism to control the expression of the bzd genes in Azoarcus strains.

Highlights

Aromatic compounds are the most widespread organic compounds in nature after carbohydrates.the release of aromatic compounds into the biosphere increased considerably over the last century as a consequence of industrial activity [1]
The anaerobic degradation of benzoate is a common feature among many strains of the Azoarcus/Aromatoleum genus [22]
PA01, we found the presence of genes homologous to the bzd genes responsible of the anaerobic degradation of benzoate in A. evansii, Azoarcus sp

Summary

Introduction

Aromatic compounds are the most widespread organic compounds in nature after carbohydrates. The release of aromatic compounds into the biosphere increased considerably over the last century as a consequence of industrial activity [1]. Many of these compounds are toxic and/or carcinogenic, representing major persistent environmental pollutants. Mainly bacteria and fungi, adapted to degrade a wide variety of aromatic compounds aerobically and/or anaerobically [2]. Many environments are anoxic and, the anaerobic degradation of aromatic compounds has great importance at the ecological level [6,7,8]

Methods

Results

Conclusion