新型噬菌体vB_RsP_sp6突破青枯劳尔氏菌胞外多糖屏障的作用方式

Ralstonia solanacearum, a gram negative bacterium that can induces plant bacterial wilt disease, resulted in severity losses in crop production worldwide. The traditional methods have limited efficacy on bacterial wilt disease controlling. Recently, phages have showed great potential in controlling bacterial wilt disease. But the exopolysaccharide (EPS) produced by R. solanacearum formed a barrier around the surface of the cell, which reduce the control efficacy of phage that used to control bacterial wilt disease. Several phages have evolved the ability to hydrolyze such barrier using a polysaccharide hydrolase and this is the only mechanism reported so far. Our team isolated a new lytic bacteriophage of R. solanacearum, vB_RsP_sp6, which can break EPS barrier. However, the genome analysis revealed that vB_RsP_sp6 has no typical EPS-hydrolyzing related genes, suggesting that the mechanism for breaking EPS barrier of this phage is new. Therefore, this project will focus on vB_RsP_sp6 and its sensitive strain, with an aim to explore the EPS-breaking related genes in vB_RsP_sp6, and further reveal the action mechanism for these factors. This project will reveal a new mechanism for phage breaking the host EPS barrier, and will also provide the theoretical basis for the control of bacterial wilt diseases with phages.

青枯劳尔氏菌引起的作物青枯病对农业生产危害巨大，传统防治措施效果不稳定。噬菌体疗法在防治青枯病方面潜力巨大，但青枯劳尔氏菌分泌的胞外多糖屏障严重影响了噬菌体对该菌的防治效果。已报道的噬菌体突破细菌胞外多糖屏障机制是噬菌体自身编码聚糖酶水解多糖，还没有其它相关机制的报道。申请人前期筛选到一株新型青枯劳尔氏菌烈性噬菌体vB_RsP_sp6具有很强的突破胞外多糖屏障的功能，但其基因组中没有编码常规降解多糖相关蛋白的基因，说明噬菌体sp6具有新的突破胞外多糖屏障的机制。本项目拟以噬菌体sp6和其敏感菌株为模型，鉴定sp6突破宿主胞外多糖屏障的关键基因，并解析其具体的作用模式。本项目将揭示一种新的噬菌体突破宿主胞外多糖屏障的机制，并可为利用噬菌体疗法防控植物青枯病提供理论依据。

青枯劳尔氏菌引起的作物青枯病对农业生产危害巨大，传统的防治措施效果不稳定。近年来，噬菌体疗法被广泛关注，在防治青枯病方面潜力巨大，但是青枯劳尔氏菌分泌的胞外多糖严重影响了噬菌体对该菌的防治效果。本课题拟通过对获得的青枯劳尔式噬菌体的全基因组的比较分析预测可能的噬菌体聚糖酶基因，通过遗传学和生物化学的方法鉴定基因的功能和作用模式。通过本项目的实施，我们分离获得了83株青枯雷尔式菌噬菌体，完成了所有分离噬菌体的基本特性研究、宿主谱检测以及22株噬菌体的全基因组测序及分析，这为后续的研究以及噬菌体功能基因的研究提供了资源。确定了噬菌体vB_RsP_sp6通过释放聚糖酶突破细菌胞外多糖屏障，基因orf84编码蛋白具有降解噬菌体胞外多糖的功能，发现噬菌体蛋白基因lys-xoo13具有裂解细菌的功能，是新型的噬菌体溶壁酶，这在防治植物细菌病害上具有潜在的应用价值。另外，开展了青枯雷尔式噬菌体防控植物青枯病的研究，证实噬菌体疗法可有效防治番茄青枯病。课题按照计划顺利进行，并取得了丰富的研究成果。