酰基高丝氨酸内脂合成酶LasI对禽致病性大肠杆菌生物学特性的影响

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

摘要:

【背景】禽致病性大肠杆菌(Avian pathogenic Escherichia coli, APEC)是禽类主要病原菌之一，群体感应(Quorum sensing, QS)系统可通过信号分子调控其生物学特性。在APEC中信号分子AHL对其生物学特性的影响目前尚不清楚。【目的】研究信号分子AHL对APEC生物学特性的影响。【方法】将含铜绿假单胞菌酰基高丝氨酸内脂合成酶(acyl-homoserine-lactone synthase，lasI)基因的表达质粒转化至APEC菌株DE17中，构建重组菌株DE17-lasI，利用LasI在DE17中合成AHL。比较野生株和重组菌株产生AHL信号分子、生长特性、生物被膜形成能力、运动性以及耐药性等生物学特性的差异；运用Real-time PCR技术，比较野生株和重组菌株中与生物被膜形成、运动性以及毒力因子相关基因的转录水平。【结果】对重组菌株AHL信号分子检测表明，DE17-lasI能够产生AHL信号分子，与野生株DE17相比，DE17-lasI生物被膜形成能力和运动性显著降低(P<0.01)，但其生长特性和耐药性无显著变化(P>0.05)；Real-time PCR检测结果表明，重组菌株的毒力因子fimH转录水平上调了58.8倍，而ompA、iss分别下调了95.4%、77.3%。与生物被膜形成相关基因agn43下调了75%，鞭毛合成基因flhA下调了80.8%。此外，AHL受体sdiA的转录水平上调了19.8倍。【结论】转化lasI至APEC中，能促进其在APEC中合成信号分子AHL，并显著影响APEC的部分生物学特性，为进一步探讨AHL型群体感应系统对APEC的调控作用提供参考。

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.