To identify new mechanisms used by pathogenic mycobacteria to secrete virulence proteins

Summary

This project aims to identify new mechanisms employed by pathogenic mycobacteria to secrete virulence proteins into the extracellular environment

Supervisor(s)

Dr Jamie Triccas

Research Location

Camperdown - Central Clinical School

Program Type

PHD

Synopsis

Secretion of proteins into the extracellular environment is important to all bacteria, and in particular mediates interactions between pathogenic bacteria and their eukaryotic hosts. In mycobacteria, there are a large number of exported mycobacterial proteins for which the mechanism of secretion is unknown. The project will use genome-wide mutational analysis to identify new protein export systems of Mycobacterium tuberculosis. We will use transposon mutagenesis, flow cytometry and sequence analysis to identify genes of mycobacteria that are required for the secretion of the proteins that are not secreted by known export systems. The identified gene products will be analysed using available databases to determine if they exhibit homology to known proteins from other organisms or form new secretion apparatus. Detailed functional analysis of the components of the identified secretion pathways and exported proteins will be performed. This would involve mutation of residues predicted to be important for secretion, and where possible the determination of crystal structure.We will also investigate the influence of the secretion system on mycobacterial virulence. The identified genes will be deleted from the M. tuberculosis genome and the ability of mutant strains to grow within mice and cause disease will be determined. If several genes appear to be responsible for the newly identified secretion apparatus, multiple gene knockout mutants will be constructed to determine if synergistic effects on protein secretion and/or pathogenicity exist. 
The identification of new protein export systems in bacteria will be not only be a significant advancement in our knowledge of bacterial physiology but will also have important implications for human health. As a large subset of secreted proteins of mycobacteria are important protective antigens and/or virulence factors, knowledge of secretion mechanisms will aid in vaccine design and deciphering mechanisms of mycobacterial pathogenicity.

Additional Information

Techniques employed by the project:

- Culture and genetic manipulation of mycobacteria (mutagenesis, gene expression)
- Cell culture and flow cytometry
- Genome database analysis
- Protein purification and related techniques (gel electrophoresis, crystallization)
- Animal models of bacterial infection

Other on-ongoing and potential research projects in the laboratory:

- Determining the role of antigen persistence in the generation of protective T cell immunity to tuberculosis
- Identification of proteins secreted by Mycobacterium tuberculosis during infection of host cells
- Developing recombinant vaccine strains engineered to target protective components of the host immune system
- Identifying novel compounds to treat infection with the lung pathogens Mycobacterium tuberculosis and Pseudomonas aeruginosa

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Keywords

Infectious Disease, tuberculosis, bacterial pathogenesis, protein secretion, molecular biology, Vaccine, immune response

Opportunity ID

The opportunity ID for this research opportunity is: 852

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