Identification of Quantitative Proteomic Differences between Mycobacterium tuberculosis Lineages with Altered Virulence.
Evidence currently suggests that as a species Mycobacterium tuberculosis exhibits very little genomic sequence diversity. Despite limited genetic variability, members of the M. tuberculosis complex (MTBC) have been shown to exhibit vast discrepancies in phenotypic presentation in terms of virulence, elicited immune response and transmissibility. Here, we used qualitative and quantitative mass spectrometry tools to investigate the proteomes of seven clinically-relevant mycobacterial strains-four M. tuberculosis strains, M. bovis, M. bovis BCG, and M. avium-that show varying degrees of pathogenicity and virulence, in an effort to rationalize the observed phenotypic differences. Following protein preparation, liquid chromatography mass spectrometry (LC MS/MS) and data capture were carried out using an LTQ Orbitrap Velos. Data analysis was carried out using a novel bioinformatics strategy, which yielded high protein coverage and was based on high confidence peptides. Through this approach, we directly identified a total of 3788 unique M. tuberculosis proteins out of a theoretical proteome of 4023 proteins and identified an average of 3290 unique proteins for each of the MTBC organisms (representing 82% of the theoretical proteomes), as well as 4250 unique M. avium proteins (80% of the theoretical proteome). Data analysis showed that all major classes of proteins are represented in every strain, but that there are significant quantitative differences between strains. Targeted selected reaction monitoring (SRM) assays were used to quantify the observed differential expression of a subset of 23 proteins identified by comparison to gene expression data as being of particular relevance to virulence. This analysis revealed differences in relative protein abundance between strains for proteins which may promote bacterial fitness in the more virulent W. Beijing strain. These differences may contribute to this strain's capacity for surviving within the host and resisting treatment, which has contributed to its rapid spread. Through this approach, we have begun to describe the proteomic portrait of a successful mycobacterial pathogen. Data are available via ProteomeXchange with identifier PXD004165.
Centre of Excellence for Biomedical TB Research, Witwatersrand University Johannesburg, South Africa.
Julian S
JS
Peters
Department of Integrative Biomedical Sciences, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town Cape Town, South Africa.
Bridget
B
Calder
VIB, Ghent University Ghent, Belgium.
Giulia
G
Gonnelli
VIB, Ghent University Ghent, Belgium.
Sven
S
Degroeve
Department of Integrative Biomedical Sciences, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town Cape Town, South Africa.
Elinambinina
E
Rajaonarifara
Department of Integrative Biomedical Sciences, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town Cape Town, South Africa.
Nicola
N
Mulder
Department of Integrative Biomedical Sciences, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town Cape Town, South Africa.
Nelson C
NC
Soares
VIB, Ghent University Ghent, Belgium.
Lennart
L
Martens
Department of Integrative Biomedical Sciences, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town Cape Town, South Africa.
Jonathan M
JM
Blackburn
Mycobacterium tuberculosis; SRM; fitness; proteomics; stress response; virulence