摘要群体感应系统调控着许多致病菌致病过程中的重要环节, 可作为合理设计抗菌药物的理想靶标, 筛选高效的群体感应抑制剂为解决细菌耐药问题提供了一个新的方向。本论文从石榴（Punica granatum）和二月兰（Orychophragmus violaceus）中分离内生菌、叶际菌，并以紫色杆菌CV026和根癌农杆菌KYC55为报告菌株，对分离到的菌株进行活性评价，以期得到具有产信号分子（QS）或群体感应抑制剂（QSI）活性的菌株。本课题从石榴茎、叶分离到15株内生细菌、24株放线菌和192株真菌，从二月兰中分离到45株叶际细菌和40株叶际真菌。结果表明，所有菌株的发酵提取物对CV026的群体感应系统均没有QSI活性，而27株石榴内生真菌对根癌农杆菌KYC55的群体感应系统具有较好的抑制活性；此外，从所获得的二月兰叶际细菌中筛选到一株具有群体感应信号分子活性的菌株。C。 violaceum中的QS系统是由LuxI/LuxR类同系物CviI/CviR构成，利用短链的C4-HSL和C6-HSL作为信号分子。而A。tumefaciens的TraI/TraR系统由traR、traM、traFB、traCBG和traI-trb操纵元组成，利用长链的（C6-C14）-HSL作为信号分子来调节群体行为。本研究表明，内生真菌所产生的代谢产物能阻断长链的信号分子与受体蛋白的结合，从而抑制A。tumefaciens的群体感应系统。本课题以石榴和二月兰为筛选样本，分别从植物组织内部和表面进行活性菌株的筛选，拓宽了QS和QSI的筛选范围，为新型天然的QS信号分子和QSI的发现提供可能的物质基础。78508

毕业论文关键词：内生菌；叶际菌；群体感应信号分子；群体感应抑制剂；报告菌株

毕业设计说明书外文摘要

Title  Quorum sensing based endophytes and phyllosphere strains isolated from two plants

Abstract Due to the important links between quorum sensing systemand numerous virus factors of pathogenic bacteria, quorum sensing system can be used as the ideal target of reasonable design of antimicrobial agents。Thus, screening effective quorum sensing inhibitors provides a new way for solving the problem of bacterial resistance。This paper focused on the isolation of endophytes and phyllosphere strains respectively from Punica granatum and Orychophragmus violaceus。The quorum sensing activities of these strains were determined by using the reporter strains Chromobacterium violaceum CV026 and Agrobacterium tumefaciens KYC55。 The purpose of this research was to get strain which could produce quorum sensing signals (QS) or quorum sensing inhibitors (QSI)。 At present, a total number of 15 endophytic bacteria, 24 actinobacteria and 192 fungi have been isolated from P。 granatum。 Furthermore, 45 phyllosphere bacteria and 40 fungi have been obtained form O。violaceus。 All strains fermentation extract on CV026 quorum-sensing system have both the activity,but among all these isolated strains 27 endophytic fungi from P。 granatum showed potent QSI activity on quorum sensing systems of A。 tumefaciens KYC55。 Besides, a phyllosphere bacterium which could produce quorum sensing signals was obtained from O。 violaceus。The QS systemof C。 violaceum is made up of CviI/CviR which are the homologues of LuxI/LuxR。 This system uses signal molecules with short chains including C4–HSL and C6–HSL。 However, the QS system of A。 tumefaciens is TraI/TraR consisted of TraR, TraM, traFB, traCBG and TraI–TRB。 It uses signal molecules with long chain (C6 ~ C14–HSL) to modulate their group behavior。 This study indicates that metabolites produced by endophytic fungi can block the long chain of signaling molecules and binds to a receptor protein, thus inhibiting A。 tumefaciens quorum sensing system。In this study, the screening of bioactive strains within or outside the plant tissues of P。 granatum and O。 violaceus respectively was investigated, which broaden the screening domains of QS and QSI。 It also serves as a new tool for finding some novel natural molecules for QS and QSI。