The adaptation of the tubercle bacillus to the host environment is likely to involve a complex set of gene regulatory events and physiological switches in response to environmental signals. In order to deconstruct the physiological state of Mycobacterium tuberculosis in vivo, we used a chemostat model to study a single aspect of the organism's in vivo state, slow growth. Mycobacterium bovis BCG was cultivated at high and low growth rates in a carbon-limited chemostat, and transcriptomic analysis was performed to identify the gene regulation events associated with slow growth. The results demonstrated that slow growth was associated with the induction of expression of several genes of the dormancy survival regulon. There was also a striking overlap between the transcriptomic profile of BCG in the chemostat model and the response of M. tuberculosis to growth in the macrophage, implying that a significant component of the response of the pathogen to the macrophage environment is the response to slow growth in carbon-limited conditions. This demonstrated the importance of adaptation to a low growth rate to the virulence strategy of M. tuberculosis and also the value of the chemostat model for deconstructing components of the in vivo state of this important pathogen.
McFadden J, Beste DJV, Kierzek AM (2012) Systems Biology of Tuberculosis, Springer
The book starts with a general introduction into the relevance of systems biology for understanding tuberculosis.
An experimental system of Mycobacterium tuberculosis growth in a carbon-limited chemostat has been
established by the use of Mycobacterium bovis BCG as a model organism. For this model, carbon-limited
chemostats with low concentrations of glycerol were used to simulate possible growth rates during different
stages of tuberculosis. A doubling time of 23 h (D 0.03 h 1) was adopted to represent cells during the acute
phase of infection, whereas a lower dilution rate equivalent to a doubling time of 69 h (D 0.01 h 1) was used
to model mycobacterial persistence. This chemostat model allowed the specific response of the mycobacterial
cell to carbon limitation at different growth rates to be elucidated. The macromolecular (RNA, DNA, carbohydrate,
and lipid) and elemental (C, H, and N) compositions of the biomass were determined for steady-state
cultures, revealing that carbohydrates and lipids comprised more than half of the dry mass of the BCG cell,
with only a quarter of the dry weight consisting of protein and RNA. Consistent with studies of other bacteria,
the specific growth rate impacts on the macromolecular content of BCG and the proportions of lipid, RNA, and
protein increased significantly with the growth rate. The correlation of RNA content with the growth rate
indicates that ribosome production in carbon-limited M. bovis BCG cells is subject to growth rate-dependent
control. The results also clearly show that the proportion of lipids in the mycobacterial cell is very sensitive to
changes in the growth rate, probably reflecting changes in the amounts of storage lipids. Finally, this study
demonstrates the utility of the chemostat model of mycobacterial growth for functional genomic, physiology,
and systems biology studies.
Lawrence ER, Arias CA, Duke B, Beste D, Broughton K, Efstratiou A, George RC, Hall LMC (2000) Evaluation of serotype prediction by cpsA-cpsB gene polymorphism in Streptococcus pneumoniae, JOURNAL OF CLINICAL MICROBIOLOGY 38 (4) pp. 1319-1323 AMER SOC MICROBIOLOGY
Brian D. Robertson and Brendan W. Wren
Beste DJV, McFadden J (2013) Metabolism of Mycobacterium tuberculosis, In: Systems biology of tuberculosis 4
Beste DJ, Nöh K, Niedenführ S, Mendum TA, Hawkins ND, Ward JL, Beale MH, Wiechert W, McFadden J (2013) (13)C-Flux Spectral Analysis of Host-Pathogen Metabolism Reveals a Mixed Diet for Intracellular Mycobacterium tuberculosis., Chem Biol 20 (8) pp. 1012-1021 Elsevier
Whereas intracellular carbon metabolism has emerged as an attractive drug target, the carbon sources of intracellularly replicating pathogens, such as the tuberculosis bacillus Mycobacterium tuberculosis, which causes long-term infections in one-third of the world's population, remain mostly unknown. We used a systems-based approach-(13)C-flux spectral analysis (FSA) complemented with manual analysis-to measure the metabolic interaction between M. tuberculosis and its macrophage host cell. (13)C-FSA analysis of experimental data showed that M. tuberculosis obtains a mixture of amino acids, C1 and C2 substrates from its host cell. We experimentally confirmed that the C1 substrate was derived from CO2. (13)C labeling experiments performed on a phosphoenolpyruvate carboxykinase mutant revealed that intracellular M. tuberculosis has access to glycolytic C3 substrates. These findings provide constraints for developing novel chemotherapeutics.
Mycobacterium tuberculosis infects a third of the world's population. Primary tuberculosis involving active fast bacterial replication is often followed by asymptomatic latent tuberculosis, which is characterised by slow or non-replicating bacteria. Reactivation of the latent infection involving a switch back to active bacterial replication can lead to post-primary transmissible tuberculosis. Mycobacterial mechanisms involved in slow growth or switching growth rate provide rational targets for the development of new drugs against persistent mycobacterial infection. Using chemostat culture to control growth rate, we screened a transposon mutant library by Transposon site hybridization (TraSH) selection to define the genetic requirements for slow and fast growth of Mycobacterium bovis (BCG) and for the requirements of switching growth rate. We identified 84 genes that are exclusively required for slow growth (69 hours doubling time) and 256 genes required for switching from slow to fast growth. To validate these findings we performed experiments using individual M. tuberculosis and M. bovis BCG knock out mutants. We have demonstrated that growth rate control is a carefully orchestrated process which requires a distinct set of genes encoding several virulence determinants, gene regulators, and metabolic enzymes. The mce1 locus appears to be a component of the switch to slow growth rate, which is consistent with the proposed role in virulence of M. tuberculosis. These results suggest novel perspectives for unravelling the mechanisms involved in the switch between acute and persistent TB infections and provide a means to study aspects of this important phenomenon in vitro.
Beste DJ, Bonde B, Hawkins N, Ward JL, Beale MH, Noack S, Nöh K, Kruger NJ, Ratcliffe RG, McFadden J (2011) ¹³C metabolic flux analysis identifies an unusual route for pyruvate dissimilation in mycobacteria which requires isocitrate lyase and carbon dioxide fixation., PLoS Pathog 7 (7)
Mycobacterium tuberculosis requires the enzyme isocitrate lyase (ICL) for growth and virulence in vivo. The demonstration that M. tuberculosis also requires ICL for survival during nutrient starvation and has a role during steady state growth in a glycerol limited chemostat indicates a function for this enzyme which extends beyond fat metabolism. As isocitrate lyase is a potential drug target elucidating the role of this enzyme is of importance; however, the role of isocitrate lyase has never been investigated at the level of in vivo fluxes. Here we show that deletion of one of the two icl genes impairs the replication of Mycobacterium bovis BCG at slow growth rate in a carbon limited chemostat. In order to further understand the role of isocitrate lyase in the central metabolism of mycobacteria the effect of growth rate on the in vivo fluxes was studied for the first time using ¹³C-metabolic flux analysis (MFA). Tracer experiments were performed with steady state chemostat cultures of BCG or M. tuberculosis supplied with ¹³C labeled glycerol or sodium bicarbonate. Through measurements of the ¹³C isotopomer labeling patterns in protein-derived amino acids and enzymatic activity assays we have identified the activity of a novel pathway for pyruvate dissimilation. We named this the GAS pathway because it utilizes the Glyoxylate shunt and Anapleurotic reactions for oxidation of pyruvate, and Succinyl CoA synthetase for the generation of succinyl CoA combined with a very low flux through the succinate--oxaloacetate segment of the tricarboxylic acid cycle. We confirm that M. tuberculosis can fix carbon from CO into biomass. As the human host is abundant in CO this finding requires further investigation in vivo as CO fixation may provide a point of vulnerability that could be targeted with novel drugs. This study also provides a platform for further studies into the metabolism of M. tuberculosis using ¹³C-MFA.
Lofthouse EK, Wheeler PR, Beste DJV, Khatri BL, Wu H, Mendum TA, Kierzek AM, McFadden J (2013) Systems-Based Approaches to Probing Metabolic Variation within the Mycobacterium tuberculosis Complex, PLOS ONE 8 (9) ARTN e75913 PUBLIC LIBRARY SCIENCE
Bakatselou C, Beste D, Kadri AO, Somanath S, Clark CG (2003) Analysis of genes of mitochondrial origin in the genus Entamoeba, JOURNAL OF EUKARYOTIC MICROBIOLOGY 50 (3) pp. 210-214 SOC PROTOZOOLOGISTS
Fotopoulou N, Tassios PT, Beste DV, Ioannidou S, Efstratiou A, Lawrence ER, Papaparaskevas J, George RC, Legakis NJ (2003) A common clone of erythromycin-resistant Streptococcus pneumoniae in Greece and the UK., Clin Microbiol Infect 9 (9) pp. 924-929
OBJECTIVE: To investigate the possible genetic relationship among erythromycin-resistant Streptococcus pneumoniae strains isolated in Greece and the UK. METHODS: During 1995-97, 140 S. pneumoniae strains were isolated from clinical specimens submitted to the microbiology departments of the two main children's hospital in Athens. All erythromycin-resistant strains were further studied with respect to the presence of genes encoding for the two major mechanisms of macrolide resistance, their serotypes, and pulsed-field gel electrophoresis (PFGE) types, in comparison to a previously characterized UK erythromycin-resistant clone. RESULTS: Eleven of the 140 isolates (7.9%) were resistant to erythromycin; nine of these were susceptible to penicillin. Serotyping allocated seven, three and one isolates to serotypes 14, 19F and serogroup 6, respectively. The mefA gene was detected in seven isolates (five serotype 14 and two serotype 19F), ermB in two (one serotype 19F and the serogroup 6 isolate), whilst in the remaining two isolates no resistance gene could be detected by polymerase chain reaction (PCR). Pulsed-field gel electrophoresis of genomic DNA showed that five Greek serotype 14 isolates belonged to the same chromosomal type as the serotype 14 erythromycin-resistant UK clone. CONCLUSIONS: The present study showed that erythromycin resistance among the S. pneumoniae isolates was mostly owing to the efflux mechanism and suggested a possible clonal spread of serotype 14 erythromycin-resistant S. pneumoniae strains between Greece and the UK.
Despite decades of research many aspects of the biology of Mycobacterium tuberculosis remain
unclear and this is reflected in the antiquated tools available to treat and prevent tuberculosis and
consequently this disease remains a serious public health problem. Important discoveries linking
M. tuberculosis?s metabolism and pathogenesis have renewed interest in this area of research.
Previous experimental studies were limited to the analysis of individual genes or enzymes whereas
recent advances in computational systems biology and high throughput experimental technologies
now allow metabolism to be studied on a genome scale. Here we discuss the progress being made
in applying system level approaches to studying the metabolism of this important pathogen.
The information from these studies will fundamentally change our approach to tuberculosis
research and lead to new targets for therapeutic drugs and vaccines.
Beste DJV, Hooper T, Stewart G, Bonde B, Avignone-Rossa C, Bushell M, Wheeler P, Klamt S, Kierzek AM, McFadden J (2007) GSMN-TB: a web-based genome scale network model of Mycobacterium tuberculosis metabolism, GENOME BIOLOGY 8 (5) ARTN r89
BIOMED CENTRAL LTD
Basu Piyali, Sandhu Noor, Bhatt Apoorva, Singh Albel, Balhana Ricardo, Gobe Irene, Crowhurst Nicola A, Mendum Thomas, Gao Liang, Ward Jane L, Beale Michael H, McFadden Johnjoe, Beste Dany (2018) The anaplerotic node is essential for the intracellular survival of Mycobacterium tuberculosis, Journal of Biological Chemistry 293 (15) pp. 5695-5704
American Society for Biochemistry and Molecular Biology
Enzymes at the phosphoenolpyruvate (PEP)?pyruvate?oxaloacetate or anaplerotic (ANA) node control the metabolic flux to glycolysis, gluconeogenesis, and anaplerosis. Here we used genetic, biochemical, and 13C isotopomer analysis to characterize the role of the enzymes at the ANA node in intracellular survival of the world's most successful bacterial pathogen, Mycobacterium tuberculosis (Mtb). We show that each of the four ANA enzymes, pyruvate carboxylase (PCA), PEP carboxykinase (PCK), malic enzyme (MEZ), and pyruvate phosphate dikinase (PPDK), performs a unique and essential metabolic function during the intracellular survival of Mtb. We show that in addition to PCK, intracellular Mtb requires PPDK as an alternative gateway into gluconeogenesis. Propionate and cholesterol detoxification was also identified as an essential function of PPDK revealing an unexpected role for the ANA node in the metabolism of these physiologically important intracellular substrates and highlighting this enzyme as a tuberculosis (TB)-specific drug target. We show that anaplerotic fixation of CO2 through the ANA node is essential for intracellular survival of Mtb and that Mtb possesses three enzymes (PCA, PCK, and MEZ) capable of fulfilling this function. In addition to providing a back-up role in anaplerosis we show that MEZ also has a role in lipid biosynthesis. MEZ knockout strains have an altered cell wall and were deficient in the initial entry into macrophages. This work reveals that the ANA node is a focal point for controlling the intracellular replication of Mtb, which goes beyond canonical gluconeogenesis and represents a promising target for designing novel anti-TB drugs.