luxS基因缺失对禽致病性大肠杆菌O1、O2和O78三种血清型分离株的生物学特性影响

Inactive luxS influence on biological characteristics of O1, O2 and O78 serotypes isolates in avian pathogenicity Escherichia coli

摘要:

[目的]LuxS/AI-2型密度群体感应系统产生的自诱导信号分子AI-2（AI-2的产生需要luxS基因编码的LuxS蛋白参与）参与对细菌众多生理功能的调控。探讨luxS对不同血清型禽致病性大肠杆菌（Avian Pathogenicity Escherichia coli，APEC）生物学特性的影响。[方法]本研究以APEC优势血清型APECO₁（O₁血清型）、DE17（O₂血清型）、E940（O₇₈血清型）及其相应luxS缺失株为研究对象，对野生株和缺失株的生长特性、生物被膜形成、rdar （red，dry and rough）形态、运动性和耐药性等特性进行分析。[结果]luxS基因的缺失不影响APEC生长特性，但导致APEC不能产生AI-2；此外，luxS基因的缺失显著降低APECO₁和E940的生物被膜形成（P<0.05），而DE17的生物被膜形成无显著变化。对各菌株的rdar形态和运动性检测结果表明，luxS基因的缺失改变了APECO₁的rdar形态，对DE17和E940并无影响；显著降低了APECO₁和DE17运动能力，对E940并无影响。荧光定量PCR检测结果表明，luxS基因的缺失显著降低APECO₁、DE17和E940与细菌运动性相关的鞭毛基因fliG和fliI的转录水平（P<0.05）。此外，对各菌株的耐药性检测结果表明，luxS基因缺失导致APECO₁对头孢吡肟和丁胺卡那由耐药变为高敏，同时对氯霉素与E940相同由高敏变为耐药，但对DE17的耐药性无显著改变。[结论]luxS对APEC的生物学特性具有重要的调控作用，且这种调控具有菌株特异性。

Abstract:

[Objective] LuxS/AI-2-type quorum sensing participates in regulation of bacterial biological properties by AI-2, which is synthesized by the enzymes LuxS (encoded by luxS). The aim of this study is to elucidate luxS effects on biological characteristics of different serotypes in Avian Pathogenic Escherichia coli (APEC).[Methods] The biological characteristics of 3 APEC strains, including APECO₁ (serotype O₁), DE17 (serotype O₂) and E940 (serotype O₇₈) and their luxS mutant strains were analysed by growth curve, biofilm-producing, rdar morphology, bacterial motility and sensitivity to antibiotics.[Results] luxS knockout, eliminating AI-2 formation, had no influence on bacterial growth, but significantly decreased biofilm-producing in E940 and APECO₁ (P<0.05), without effect on DE17. Results of rdar morphology indicate that the APECO₁ strain showed remarkable change in rdar morphology compared with luxS mutant, but no change in DE17 and E940. Moreover, deletion of luxS lead to decreasing the motility of APECO₁ and DE17, but no influence on E940 strain. The transcriptional levels of fliG and fliI were significantly decreased in APECO1, DE17 and E940 (P<0.05). Furthermore, results of drug-resistance indicate that luxS inactivation caused APECO₁ resistant to cefepime, amikacin, and sensitive to chloramphenicol. luxS inactivation also caused E940 strain sensitive to chloramphenicol, but no significant effect on drug-resistance of DE17 strain.[Conclusion] LuxS plays a significant role in regulation of biological properties in APEC.