报告题目: Identification and characterization of type III secretion system (T3SS) effectors in Edwardsiella tarda.
报告人: Leung Ka Yin (广东以色列理工学院教授)
报告时间: 12月21日 (周四) 上午 10:00-12:00
报告地点: 科技楼201
报告摘要:
Edwardsiella tarda has a board host range and causes severe fish losses in the aquaculture industry worldwide. E. tarda enters the fish through the gastrointestinal tract and skin. It then invades and replicates inside epithelial and phagocytic cells, spread to surrounding tissues and organs, and eventually kill the fish by systemic infection. Among the known virulence mechanisms in this organism, type III and type VI secretion system (T3SS and T6SS) are the bacterium’s most lethal weapons against the host defense.
My laboratory discovered a T3SS and a T6SS gene clusters in E. tarda; mutations in these clusters resulted in virulence attenuation of 1 to 2 logs in LD50 values. T3SS effector proteins are directly inject into host cells through nano-secretion machineries called injectisomes. These effectors have diverse functions that target specific host proteins to disrupt as well as mimic host cellular processes, and interfere with the host immunity. One area of my research is to identify effectors of T3SS and characterize them individually and collectively in order to understand their unique functions. We have used several approaches to identify T3SS effector, such as transcriptome analysis, homology search and machine learning. The machine learning approach has been used to predict T3SS effectors based on the translocation signals embedded in the effector sequences. Our effector prediction method called Genome Search for Effector Tool (GenSET) gave better performance values than six published programs and predicts more effectors in four bacterial genomes. The next step is to train GenSET for family-specific T3SS effector prediction and then apply the program to Edwardsiella strains for T3SS effector prediction. Characterization of effectors can take several approaches such as the use of sequence homology analysis, identification of targeted proteins in hosts, location of effectors inside the host cell, or screening against known virulent phenotypes such as intracellular living or host-alteration phenotypes. For example, we found a microtubule disassembly phenotype upon E. tarda infection of HeLa cells. We screened for this phenotype against a defined transposon mutant library of ~2,700+ mutants and obtained 15 genes that might be responsible for the microtubule disassembly phenotype.
Effector studies in E. tarda will generate important fundamental knowledge on host-pathogen interactions. This knowledge will be useful for future vaccine and novel therapeutics development. Knowledge and technologies developed in this project can be applied to the study of T6SS effectors as well as to the effector studies of other fish pathogens. This will give us a better understanding of the biology and functions of effectors in gram-negative bacterial pathogens. Furthermore, E. tarda can serve as a model organism for studies of other fish diseases as well as human diseases since Edwardsiella belongs to the family of Enterobacteriaceae that contains many important food- and water-borne human pathogens.
报告人简介:
Leung Ka Yin教授于1980年毕业于加拿大萨斯喀彻温大学应用微生物和食品科学系, 1982年在加拿大萨斯喀彻温大学应用微生物和食品科学系获硕士学位, 1987年在圭尔夫大学微生物学博士。1994年到2008年，梁教授在新加坡国立大学任讲师，高级讲师，副教授；2008年到2017年在加拿大西三一大学生物系任教授；2018年起任广东以色列理工教授。
梁教授主要从事鱼类细菌病的研究，包括致病机理，病原宿主相互作用，新致病因子的识别等。迄今为止，梁教授已发表文章58篇，总引用率2500余次，H-index:28。
欢迎全校师生参加！
注：本次讲座将纳入海洋生命学科继续教育课程。
理学院
2017.12.17
