Project description:Mycobacterial Ser/Thr kinases play a critical role in bacterial physiology and pathogenesis. Linking kinases to the substrates they phosphorylate in vivo, thereby elucidating their exact functions, is still a challenge. The aim of this work was to associate protein phosphorylation in mycobacteria with important subsequent macro cellular events by identifying the physiological substrates of PknG in Mycobacterium bovis BCG. The study compared the phosphoproteome dynamics during the batch growth of M. bovis BGC versus the respective PknG knock-out mutant (ΔPknG-BCG) strains.
Project description:Mycobacteria naturally grow as corded biofilms in liquid media without detergent. Such detergent-free biofilm phenotypes may reflect the growth pattern of bacilli in tuberculous lung lesions. New strategies are required to treat tuberculosis that is responsible for more deaths each year than any other bacterial disease. The lengthy six-month regimen for drug-sensitive tuberculosis is necessary to remove antimicrobial drug tolerant populations of bacilli that persist through drug therapy. The role of biofilm-like growth in the generation of these sub-populations remains poorly understood despite the hypothesized clinical significance and mounting evidence of biofilms in pathogenesis. We adapted a three-dimensional Rotary Cell Culture System to model M. bovis BCG biofilm growth in low-shear detergent-free liquid suspension. Importantly, biofilms formed without attachment to artificial surfaces and without severe nutrient starvation or environmental stress. Biofilm-derived planktonic bacilli were tolerant to isoniazid and streptomycin, but not rifampicin. This phenotypic drug tolerance was lost after passage in drug-free media. Transcriptional profiling revealed induction of cell surface regulators, sigE and BCG_0559c alongside the ESX-5 secretion apparatus in these low-shear liquid-suspension biofilms. Supernatant from biofilms induced greater pro-inflammatory cytokine release from macrophages. This study engineers and characterizes mycobacteria grown as a suspended biofilm, illuminating new drug discovery pathways for this deadly disease.
Project description:Despite wide scale vaccination with Mycobacterium bovis BCG, the prevalence of tuberculosis remains high, reflecting the global variable efficacy of this vaccine against adult pulmonary TB. Characterisation of different immune responses to M. tuberculosis and M. bovis BCG would increase understanding of pathology following M. tuberculosis infection or reactivation, and would facilitate the rational design of a new vaccine. Gene expression profiling was conducted on samples from diluted whole blood cultures from three healthy donors following incubation with live mycobacteria for six days. Approximately 8,000 gene entities were at least two-fold up- or down- regulated by the mycobacteria, and both mycobacteria induced similar expression changes in approximately 2,300 genes. Strikingly, many genes exhibited qualitatively different expression patterns, with over 1,000 genes up-regulated in response to M. bovis BCG but not changed by M. tuberculosis. Gene Ontology analysis revealed that the genes which failed to upregulate in M. tuberculosis-infected cultures included a large proportion of genes with lysosomal function. The inhibited up-regulation of expression of IFN-γ-inducible protein 30, acid phosphatase 2, cathepsin B and GM2 ganglioside activator was verified in samples from six biologically independent donors by qRT-PCR. The failure to up-regulate these genes in response to M. tuberculosis may constitute an immune evasion mechanism, preventing intracellular killing and antigen presentation.