Whole-Genome Sequencing Analysis of Quorum Quenching Bacterial Strain Acinetobacter lactucae QL-1 Identifies the FadY Enzyme for Degradation of the Diffusible Signal Factor

Abstract

The diffusible signal factor (DSF) is a fatty acid signal molecule and is widely conserved in various Gram-negative bacteria. DSF is involved in the regulation of pathogenic virulence in many bacterial pathogens, including Xanthomonas campestris pv. campestris (Xcc). Quorum quenching (QQ) is a potential approach for preventing and controlling DSF-mediated bacterial infections by the degradation of the DSF signal. Acinetobacter lactucae strain QL-1 possesses a superb DSF degradation ability and effectively attenuates Xcc virulence through QQ. However, the QQ mechanisms in strain QL-1 are still unknown. In the present study, whole-genome sequencing and comparative genomics analysis were conducted to identify the molecular mechanisms of QQ in strain QL-1. We found that the fadY gene of QL-1 is an ortholog of XccrpfB, a known DSF degradation gene, suggesting that strain QL-1 is capable of inactivating DSF by QQ enzymes. The results of site-directed mutagenesis indicated that fadY is required for strain QL-1 to degrade DSF. The determination of FadY activity in vitro revealed that the fatty acyl-CoA synthetase FadY had remarkable catalytic activity. Furthermore, the expression of fadY in transformed Xcc strain XC1 was investigated and shown to significantly attenuate bacterial pathogenicity on host plants, such as Chinese cabbage and radish. This is the first report demonstrating a DSF degradation enzyme from A. lactucae. Taken together, these findings shed light on the QQ mechanisms of A. lactucae strain QL-1, and provide useful enzymes and related genes for the biocontrol of infectious diseases caused by DSF-dependent bacterial pathogens.

Exploration of the Quorum-Quenching Mechanism in Pseudomonas nitroreducens W-7 and Its Potential to Attenuate the Virulence of Dickeya zeae EC1

“…Among these, the use of QQ bacteria or QQ enzymes has appeared as an efficient tool for managing plant diseases ( Uroz et al, 2009 ). Several QQ strains such as Cupriavidus sp., A. lactucae , Burkholderia anthina , O. intermedium , Bacillus sp., Variovorax sp., Variovorax paradoxus , and A. tumefaciens have been discovered and applied as tools for the biocontrol of plant diseases ( Ha et al, 2018 ; Ye et al, 2019 , 2020b , c ; Fan et al, 2020 ). The expression of QQ hydrolytic enzymes (AttM and AiiA) quenched virulence in the pathogenic bacteria Dickeya spp.…”

“…Several QQ genes have been identified, such as aiiA (the first) of Bacillus sp. ( Dong et al, 2000 ), aiiM of Microbacterium testaceum ( Wang et al, 2010 ), attM of Agrobacterium fabrum ( Khan and Farrand, 2009 ), ytnP of Bacillus subtilis ( Schneider et al, 2012 ), and fadY of Acinetobacter lactucae ( Ye et al, 2020b ). Previous research studies have demonstrated that bacteria or AHL-lactonase could reduce pathogenicity and protect hosts against Gram-negative pathogenic bacteria ( Torres et al, 2016 ).…”

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

“…As for the control of diseases caused by bacteria, the use of QQ is a promising avenue to replace traditional antibiotics. In principle, QQ quenches the QS molecules of targeted bacteria, resulting in the shutdown of the expression of QS-controlled virulence genes [61][62][63][64]. As a result, a variety of bacteria that degrade DSF have been found and characterized, including Staphylococcus, Bacillus, Microbacterium, Paenibacillus, Cupriavidus, Acinetobacter, and Pseudomonas [15,[65][66][67][68][69].…”

The Clash of Microbiomes: From the Food Matrix to the Host Gut

“…The high accessibility of sequencing platforms and predictive biology algorithms can support this objective. Indeed, gene mining can inform us about the metabolic preferences and biosynthetic capability of strains, about microbe-microbe interactions and quorum sensing, or about the production of antimicrobial compounds that could burden the food or gut microbiome [65][66][67]. In this context, trophic network analysis can also provide insights into mechanisms of co-dependency or antagonism between microbes [27].…”