Identification of FadT as a Novel Quorum Quenching Enzyme for the Degradation of Diffusible Signal Factor in Cupriavidus pinatubonensis Strain HN-2.

Xudan Xu,Weijun Dai,Shaohua Chen,Xiaofan Zhou,Tian Ye,Wenping Zhang,Tian Zhou

doi:10.3390/ijms22189862

Abstract

Quorum sensing (QS) is a microbial cell–cell communication mechanism and plays an important role in bacterial infections. QS-mediated bacterial infections can be blocked through quorum quenching (QQ), which hampers signal accumulation, recognition, and communication. The pathogenicity of numerous bacteria, including Xanthomonas campestris pv. campestris (Xcc), is regulated by diffusible signal factor (DSF), a well-known fatty acid signaling molecule of QS. Cupriavidus pinatubonensis HN-2 could substantially attenuate the infection of XCC through QQ by degrading DSF. The QQ mechanism in strain HN-2, on the other hand, is yet to be known. To understand the molecular mechanism of QQ in strain HN-2, we used whole-genome sequencing and comparative genomics studies. We discovered that the fadT gene encodes acyl-CoA dehydrogenase as a novel QQ enzyme. The results of site-directed mutagenesis demonstrated the requirement of fadT gene for DSF degradation in strain HN-2. Purified FadT exhibited high enzymatic activity and outstanding stability over a broad pH and temperature range with maximal activity at pH 7.0 and 35 °C. No cofactors were required for FadT enzyme activity. The enzyme showed a strong ability to degrade DSF. Furthermore, the expression of fadT in Xcc results in a significant reduction in the pathogenicity in host plants, such as Chinese cabbage, radish, and pakchoi. Taken together, our results identified a novel DSF-degrading enzyme, FadT, in C. pinatubonensis HN-2, which suggests its potential use in the biological control of DSF-mediated pathogens.

Highlights

Black rot, caused by Xanthomonas campestris pv. campestris (Xcc), is a worldwide threat to plants
Our findings revealed the molecular basis of highly efficient diffusible signal factor (DSF)-degrading C. pinatubonensis HN-2 and indicated useful genes and agents that show potential for biocontrol of black rot and other infectious diseases caused by DSF-dependent bacterial pathogens
The whole genome of C. pinatubonensis HN-2 was sequenced by both Illumina shortread and Oxford Nanopore long-read sequencing technologies, generating 4.29 and 1.63 Gb of sequencing data, respectively

Summary

Introduction

Black rot, caused by Xanthomonas campestris pv. campestris (Xcc), is a worldwide threat to plants. Campestris (Xcc), is a worldwide threat to plants. Black rot, caused by Xanthomonas campestris pv. QS controls a variety of pathogen-mediated diseases in humans, animals, and plants [2]. Xcc produces a series of extracellular enzymes that are important in bacterial pathogenesis. This process is linked to the signaling molecule diffusible signal factor (DSF), which was previously identified as cis-11-methyl-2-dodecenoic acid. DSF family members’ signals are linked to bacterial toxicity, biofilm development, and pathogen antibiotic tolerance [7]. The main means of prevention and control of black rot are chemical pesticides and antibiotics. For the consideration of human health and social security, it is becoming important to find a late-model, effective, and safe prevention and control measure

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Results

Conclusion