Effect of acyl homoserine lactone synthase LasI on the biological characteristics of avian pathogenic Escherichia coli

Abstract:

[Background] Avian pathogenic Escherichia coli (APEC) is one of the main pathogens of poultry. The quorum sensing (QS) system regulates its biological properties through signaling molecules. Currently, the effect of the signaling molecule AHLs on its biological properties in APEC is unclear. [Objective] To study the effect of AHL on the biological characteristics of APEC. [Methods] The plasmid containing the acyl-homoserine-lactone synthase (lasI) gene was transformed into the DE17 strain of APEC to construct the recombinant strain DE17-lasI. Then the biological characteristics, including AHLs production, growth characteristics, biofilm formation ability, motility and drug resistance was compared between DE17 and DE17-lasI, respectively. Besides, the transcriptional levels of virulence genes, biofilm formation related genes and flagellin synthesis genes of wild and recombination strain were compared by real-time PCR. [Results] The level of AHL produced by DE17-lasI was significantly enhanced (P<0.01), while the biofilm formation and motility were significantly decreased (P<0.01) compared with the wild strain DE17. However, the growth characteristics and drug resistance were no significant change (P>0.05) between DE17 and DE17-lasI. Furthermore, the results showed that the transcription level of virulence factor fimH of the DE17-lasI was up-regulated by 58.8 times, while ompA and iss were down-regulated by 95.4% and 77.3% times compared with DE17, respectively. The biofilm formation related gene agn43 and the flagellar synthesis gene flhA was down-regulated by 75% and 80.8%, respectively. In addition, the transcription level of the AHL receptor sdiA was up-regulated by 19.8-fold. [Conclusion] Transformation of lasI into APEC can promote the synthesis of AHL in APEC, which significantly affect some biological characteristics of APEC. This study provides a reference for further study on the regulation of AHLs in APEC.

Key words:Avian pathogenic Escherichia coli, Quorum sensing, lasI, Acyl-homoserine-lactone, Biofilm, Motility