Kill or be killed : the dangerous Type VI Secretion System game played by Xanthomonas translucens pathovar undulosa

Details

Supervisors

Bragard, Claude ; Peduzzi, Chloé

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences agronomiques, à finalité spécialisée

Abstract

Xanthomonas translucens is threatening cereal crops around the world. During plant infection, this bacterium might also face a wide variety of microbial competitors able to prevent infection and niche colonization. Although plants are using various defense mechanisms such as promoting epiphytic symbiotic bacteria, X. translucens strains may overwhelm these bacterial competitors through their Type VI Secretion System or T6SS. This secretion system is a close dependent contractile nanomachine used during interbacterial competition to inject protein effectors into target procaryotic and/or eukaryotic cells. However, little is known about the T6SS function of X. translucens plant pathogens, since most studies have been conducted on the T6SSs of human pathogens such as Pseudomonas aeruginosa and Vibrio cholerae. Although three different clades have been evidenced for X. translucens T6SS, all of them are not necessarily present in every strain (clade i3*, i3***, and i4). The clade i3*** is very conserved in the X. translucens pathovars cerealis, translucens and undulosa while the clade i4 is not, and some translucens strains have instead a Type IV Secretion System, also supposed to be involved in interbacterial competition. A reliable way to determine the function of the T6SS clades i3*** and i4 of X. translucens is by using mutants, and by reverse complementation of the altered function. Here, we produced some T6SS mutants and explored the function(s) of both clades. Furthermore, we designed two new protocols, one for interbacterial competition, and another one for bacterial conjugation to bridge the difficulties and inconsistency of electroporation for X. translucens transformation.