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B 7 The role of Epstein-Barr virus-induced gene 3 (EBI3) cytokines IL-27 and IL-35 in bacterial inflammation

Principal investigator
Markus Neurath, Stefan Wirtz

Mentor
Christian Berens

PhD exam: 22.06.2015

Role of the Type VI secretion system (T6SS) in the host-pathogen and microbial interactions

T6SS are recently discovered protein transport machinery in most of the Gram negative bacteria. T6SS are tightly regulated with other virulence determinants like flagella synthesis, quorum sensing and T3SS. Apart from their role in virulence mechanisms it has now also been shown to play some role in interbacterial communication. Citrobacter rodentium is a Gram negative bacterium and highly infectious enteric pathogen, causing colitis and transmissible colonic hyperplasia in mice by attaching and effacing lesions in the intestinal epithelium, like it's human counterpart enteropathogenic and enterohemorrhagic E. coli (EPEC and EHEC respectively). Recently in the course of C. rodentium genome sequencing project a T6SS comprising of 2 types of clusters have been identified in C. rodentium. However the functions of these two clusters are still unknown, therefore the C. rodentium is a very promising model for studying the role of T6SS with respect to the intestinal inflammation.
Although there have been some work which strongly suggests that some secreted T6SS proteins such as VgrG and Hcp of pathogenic bacteria like V. cholerae, A. hydrophila, and B. pseudomallei causes immunological and cellular alterations, the identification of potential interacting partners in host cells are yet to be done. It would also be interesting to study the role of T6SS on interbacterial communication since it has already been shown that the dysbiosis in the gut microflora can cause disease like Inflammatory Bowel Disease (IBD). H. hepaticus is a pathobiont which causes chronic inflammatory response similar to human IBD, and interestingly the T6SS have been reported to mediate critical protective functions during it's association with mammalian host cells. Therefore detail study of the T6SS could be a very important and promising target for the development of vaccine and new approaches to diagnosis for IBD and colon cancer.
In order to achieve the goal we are currently using C. rodentium as a model organism which is a well known experimental colitis model. To investigate the effect of T6SS effector proteins on host we will study the expression of codon optimized Hcp and VgrG genes in different cell lines on one hand while on the other hand we will generate different T6SS gene knockouts of C. rodentium strain. Apart from the VgrG and Hcp we will also generate other important T6SS genes knockout strains like Icmf and ClpV to study their effects on C. rodentium colonization capacity in mice. These mutant strains will be further fluorescent tagged to perform in vivo studies for the identification of the potential interacting partners in host cells.

Figure: Putative model showing the assembly and function of T6SS. Cascales Embo reports, 2008.
J, L, M and H - TssJ, TssL, TssM and TssH respectively; ClpV multimer indicated by red circles and the putative lipoprotein as a protein multimer with orange, blue, pink and grey subunits.

 

Publications

 

Presentations

July 2014 6th Annual Retreat, Erlangen School of Molecular Communication, Kloster Banz, Bad Staffelstein, Germany
“Functional analysis of T6SS (Type 6 Secretion System) as an important factor for pathogenecity of C. rodentium
Talk
     
July 2013 5th Annual Retreat, Erlangen School of Molecular Communication, Kloster Banz, Bad Staffelstein, Germany
Functional Analysis of T6SS (Type 6 Secretion System) as an Important Factor for pathogenicity of C. rodentium
Talk
     
July 2012 4th Annual Retreat, Erlangen School of Molecular Communication, Kloster Banz, Bad Staffelstein, Germany
Functional Analysis of Type six secretion system (T6SS) in C. rodentium infection
Poster
     
October 2011 First International SFB 796 Conference: Mechanisms of viral host cell manipulations: from plants to humans, Bamberg, Germany
The role of type VI secretion system (T6SS) in the host-pathogen and interbacterial interactions
Poster
     
July 2011 3rd Annual Retreat, Erlangen School of Molecular Communication, Kloster Banz, Bad Staffelstein, Germany
The Analysis of T6SS as an important factor in pathogenicity of C. rodentium and EHEC
Talk and Poster
     

 

Awards

Best Poster Award
4th Annual Retreat, Erlangen School of Molecular Communication
Kloster Banz, Bad Staffelstein, Germany, July 2012
Functional Analysis of Type six secretion system (T6SS) in C. rodentium infection