Mycobacterium tuberculosis capsular alpha-glucan biosynthesis and characterisation of host-pathogen interactions

Lead Research Organisation: University of Birmingham
Department Name: Sch of Biosciences


Like many bacterial species, Mycobacterium tuberculosis, the bacterium that causes TB, is covered with an outer capsule composed of sugar polymers. These so called sugar capsules have been shown to be important for bacterial virulence by undermining the host immune response. Although, the composition of the M. tuberculosis capsule is
relatively well studied, the mechanism underlying its production and its functional role have only been poorly defined. The aim of this project is to obtain an insight into these two important issues. Firstly, we will address, in detail, the route by which the capsule is produced, and secondly, we will study the capsule?s functional role under various
experimental conditions. Together, the data will provide valuable insight into the nature and function of this long neglected structure.

Technical Summary

Our main objective is to define the pathways leading to the biosynthesis and transport of capsular alpha-glucans in Mycobacterium tuberculosis and to assess the functional role of this major polysaccharide in pathogenesis. We plan to achieve this by working towards the following aims:

(1) Identify the genes involved in the biosynthesis of alpha-glucan.

(2) Identify the genes involved in the transport of alpha-glucan.

(3) Assess the role of alpha-glucan in the virulence of M. tuberculosis.

We have already identified potential candidate genes using bioinformatic tools and plan to generate either null or conditional mutants (for genes predicted to be essential) in M. tuberculosis. We propose to chemically characterise the mutants with respect to alpha-glucan content and to elucidate the role of individual genes in capsular biosynthesis. As a parallel approach, we will also screen a M. tuberculosis transposon library with an anti alpha-glucan antibody to identify mutants defective in biosynthesis/transport. In addition,
functional characterisation of proteins will also be carried out using established enzyme assays. Finally, mutant strains, purified alpha-glucan and chemically characterised intermediates will be examined in both macrophages and in mice to assess any changes in virulence to clarify the functional role of the alpha-glucan in the Mycobacterium-host interaction.


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Description Programme Grant
Amount £1,778,106 (GBP)
Funding ID MR/K012118/1 
Organisation Medical Research Council (MRC) 
Sector Public
Country United Kingdom
Start 06/2013 
End 05/2018
Description The Mycobacterium tuberculosis Cell Envelope: unravelling complex cell wall assembly, degradation and re-cycling pathways
Amount £1,720,866 (GBP)
Funding ID MR/S000542/1 
Organisation Medical Research Council (MRC) 
Sector Public
Country United Kingdom
Start 03/2019 
End 02/2024