Structure and function of mycobacterium glycopeptidolipids from comparative genomics perspective

Thymol as Biofilm and Efflux Pump Inhibitor: A Dual-Action Approach to Combat Mycobacterium tuberculosis

Tuberculosis (TB) remains a significant global health challenge, exacerbated by the emergence of drug-resistant strains of Mycobacterium tuberculosis (M. tb). The complex biology of M. tb, particularly its key porins, contributes to its resilience against conventional treatments, highlighting the exploration of innovative therapeutic strategies. Following with this challenges, the present study investigates the bioactivity properties of phenolic compounds derived from the terpene groups, specifically through Thymol (THY) against M. smegmatis as a surrogated model for M. tb. Furthermore, the study employed with combination of two approaches i.e., in vitro assays and computational methods to evaluate the efficacy of THY against M. smegmatis and its interaction with M. tb biofilm and efflux pump proteins, particularly Rv1258c and Rv0194. The in vitro findings demonstrated that THY exhibits inhibitory activity against M. smegmatis and shows promising interaction with a combination of isoniazid (INH) and rifampicin (RIF) of TB regimens. Furthermore, THY demonstrated significant inhibitory action towards motility and biofilm formation of M. smegmatis. The combination of THY with INH and RIF exhibited a synergistic effect, enhancing the overall antimicrobial efficacy. Additionally, THY displayed reactive oxygen species (ROS) activity and potential efflux pump inhibitory action towards M. smegmatis. The computational analysis revealed that THY interacts effectively with efflux pump proteins Rv1258c and Rv0194, showing superior binding affinity compared to verapamil, a known efflux pump inhibitor. Pharmacokinetic studies highlighted that THY possess a favourable safety profile. In conclusion, THY represents a promising inhibitory compound for tuberculosis prevention, potentially addressing challenges posed by drug resistance.

Ajoene: a natural compound with enhanced antimycobacterial and antibiofilm properties mediated by efflux pump modulation and ROS generation against M. Smegmatis

Tuberculosis (TB) continues to be a primary worldwide health concern due to relatively ineffective treatments. The prolonged duration of conventional antibiotic therapy warrants innovative approaches to shorten treatment courses. In response to challenges, the study explores potential of Ajoene, a naturally occurring garlic extract-derived compound, for potential TB treatment. Mycobacterium smegmatis as a model organism for M. tuberculosis (M. tb) to investigate Ajoene's efficiency. In vitro techniques like antimicrobial susceptibility, antibiofilm, EtBr accumulation assay, and ROS assay evaluate the potency of Ajoene and conventional TB drugs against Mycobacterium smegmatis. An in-silico study also investigated the interaction between Ajoene and quorum-sensing proteins, specifically regX3, MSMEG_5244, and MSMEG_3944, which are involved in biofilm formation and sliding activity. In vitro findings revealed that Ajoene exhibited significant antibacterial activity by inhibiting growth and showing bactericidal effects. It also demonstrated additive interactions with common antibiotics such as Isoniazid and Rifampicin. Furthermore, Ajoene demonstrated a comparative interaction with commonly used antibiotics, such as Isoniazid and Rifampicin, and reduced M. smegmatis motility, both alone and in combination with these antibiotics. In silico analysis shows that Ajoene exhibited a higher binding affinity with regX3, a protein orthologous to the regX3 gene in M.tb. Ajoene also demonstrated consistent antibiofilm effects, particularly when combined synergistically with Isoniazid and Rifampicin. Mechanistic investigations demonstrated Ajoene's potential to inhibit efflux pumps and promote ROS generation in bacteria, suggesting a potential direct killing mechanism. Collectively, the findings emphasize Ajoene's effectiveness as a novel antimycobacterial and antibiofilm molecule for TB treatment.

Decoding the role of mycobacterial lipid remodelling and membrane dynamics in antibiotic tolerance

Current treatments for tuberculosis primarily target Mycobacterium tuberculosis (Mtb) infections, often neglecting the emerging issue of latent tuberculosis infection (LTBI) which are characterized by reduced susceptibility to antibiotics. The bacterium undergoes multiple adaptations during dormancy within host granulomas, leading to the development of antibiotic-tolerant strains. The mycobacterial membrane plays a crucial role in drug permeability, and this study aims to characterize membrane lipid deviations during dormancy through extensive lipidomic analysis of bacteria cultivated in distinct media and growth stages. The results revealed that specific lipids localize in different regions of the membrane envelope, allowing the bacterium to adapt to granuloma conditions. These lipid modifications were then correlated with the biophysical properties of the mycomembrane, which may affect interactions with antibiotics. Overall, our findings offer a deeper understanding of the bacterial adaptations during dormancy, highlighting the role of lipids in modulating membrane behaviour and drug permeability, ultimately providing the groundwork for the development of more effective treatments tailored to combat latent infections.

Deciphering the biosynthesis of a novel lipid in Mycobacterium tuberculosis expands the known roles of the nitroreductase superfamily

Mycobacterium tuberculosis's (Mtb) success as a pathogen is due in part to its sophisticated lipid metabolic programs, both catabolic and biosynthetic. Several of Mtb lipids have specific roles in pathogenesis, but the identity and roles of many are unknown. Here, we demonstrated that the tyz gene cluster in Mtb, previously implicated in resistance to oxidative stress and survival in macrophages, encodes the biosynthesis of acyl-oxazolones. Heterologous expression of tyzA (Rv2336), tyzB (Rv2338c) and tyzC (Rv2337c) resulted in the biosynthesis of C12:0-tyrazolone as the predominant compound, and the C12:0-tyrazolone was identified in Mtb lipid extracts. TyzA catalyzed the N-acylation of l-amino acids, with highest specificity for l-Tyr and l-Phe and lauroyl-CoA (kcat/KM = 5.9 ± 0.8 × 103 M-1s-1). In cell extracts, TyzC, a flavin-dependent oxidase (FDO) of the nitroreductase (NTR) superfamily, catalyzed the O2-dependent desaturation of the N-acyl-L-Tyr produced by TyzA, while TyzB, a ThiF homolog, catalyzed its ATP-dependent cyclization. The substrate preference of TyzB and TyzC appear to determine the identity of the acyl-oxazolone. Phylogenetic analyses revealed that the NTR superfamily includes a large number of broadly distributed FDOs, including five in Mtb that likely catalyze the desaturation of lipid species. Finally, TCA1, a molecule with activity against drug-resistant and persistent tuberculosis, failed to inhibit the cyclization activity of TyzB, the proposed secondary target of TCA1. Overall, this study identifies a novel class of Mtb lipids, clarifies the role of a potential drug target, and expands our understanding of the NTR superfamily.

New therapeutic strategies for Mycobacterium abscessus pulmonary diseases - untapping the mycolic acid pathway

INTRODUCTION

Treatment options against Mycobacterium abscessus infections are very limited. New compounds are needed to cure M. abscessus pulmonary diseases. While the mycolic acid biosynthetic pathway has been largely exploited for the treatment of tuberculosis, this metabolic process has been overlooked in M. abscessus, although it offers many potential drug targets for the treatment of this opportunistic pathogen.

AREAS COVERED

Herein, the authors review the role of the MmpL3 membrane protein and the enoyl-ACP reductase InhA involved in the transport and synthesis of mycolic acids, respectively. They discuss their importance as two major vulnerable drug targets in M. abscessus and report the activity of MmpL3 and InhA inhibitors. In particular, they focus on NITD-916, a direct InhA inhibitor against M. abscessus, particularly warranted in the context of multidrug resistance.

EXPERT OPINION

There is an increasing body of evidence validating the mycolic acid pathway as an attractive drug target to be further exploited for M. abscessus lung disease treatments. The NITD-916 studies provide a proof-of-concept that direct inhibitors of InhA are efficient in vitro, in macrophages and in zebrafish. Future work is now required to improve the activity and pharmacological properties of these inhibitors and their evaluation in pre-clinical models.

Genetic diversification of persistent Mycobacterium abscessus within cystic fibrosis patients

Mycobacterium (M.) abscessus infections in Cystic Fibrosis (CF) patients cause a deterioration of lung function. Treatment of these multidrug-resistant pathogens is associated with severe side-effects, while frequently unsuccessful. Insight on M. abscessus genomic evolvement during chronic lung infection would be beneficial for improving treatment strategies. A longitudinal study enrolling 42 CF patients was performed at a CF center in Berlin, Germany, to elaborate phylogeny and genomic diversification of in-patient M. abscessus. Eleven of the 42 CF patients were infected with M. abscessus. Five of these 11 patients were infected with global human-transmissible M. abscessus cluster strains. Phylogenetic analysis of 88 genomes from isolates of the 11 patients excluded occurrence of M. abscessus transmission among members of the study group. Genome sequencing and variant analysis of 30 isolates from 11 serial respiratory samples collected over 4.5 years from a chronically infected patient demonstrated accumulation of gene mutations. In total, 53 genes exhibiting non-synonymous variations were identified. Enrichment analysis emphasized genes involved in synthesis of glycopeptidolipids, genes from the embABC (arabinosyltransferase) operon, betA (glucose-methanol-choline oxidoreductase) and choD (cholesterol oxidase). Genetic diversity evolved in a variety of virulence- and resistance-associated genes. The strategy of M. abscessus populations in chronic lung infection is not clonal expansion of dominant variants, but to sustain simultaneously a wide range of genetic variants facilitating adaptation of the population to changing living conditions in the lung. Genomic diversification during chronic infection requires increased attention when new control strategies against M. abscessus infections are explored.

Chain release mechanisms in polyketide and non-ribosomal peptide biosynthesis

Review covering up to mid-2021The structure of polyketide and non-ribosomal peptide natural products is strongly influenced by how they are released from their biosynthetic enzymes. As such, Nature has evolved a diverse range of release mechanisms, leading to the formation of bioactive chemical scaffolds such as lactones, lactams, diketopiperazines, and tetronates. Here, we review the enzymes and mechanisms used for chain release in polyketide and non-ribosomal peptide biosynthesis, how these mechanisms affect natural product structure, and how they could be utilised to introduce structural diversity into the products of engineered biosynthetic pathways.

Ultrastructure of the Mycobacterium avium subsp. hominissuis Biofilm

Mycobacterium avium subsp. hominissuis (MAH) is one of the most common nontuberculous mycobacterial pathogens responsible for chronic lung disease in humans. It is widely distributed in biofilms in natural and living environments. It is considered to be transmitted from the environment. Despite its importance in public health, the ultrastructure of the MAH biofilm remains largely unknown. The ultrastructure of a MAH-containing multispecies biofilm that formed naturally in a bathtub inlet was herein reported along with those of monoculture biofilms developed from microcolonies and pellicles formed in the laboratory. Scanning electron microscopy revealed an essentially multilayered bathtub biofilm that was packed with cocci and short and long rods connected by an extracellular matrix (ECM). Scattered mycobacterium-like rod-shaped cells were observed around biofilm chunks. The MAH monoculture biofilms that developed from microcolonies in vitro exhibited an assembly of flat layers covered with thin film-like ECM membranes. Numerous small bacterial cells (0.76±0.19‍ ‍μm in length) were observed, but not embedded in ECM. A glycopeptidolipid-deficient strain did not develop the layered ECM membrane architecture, suggesting its essential role in the development of biofilms. The pellicle biofilm also consisted of flat layered cells covered with an ECM membrane and small cells. MAH alone generated a flat layered biofilm covered with an ECM membrane. This unique structure may be suitable for resistance to water flow and disinfectants and the exclusion of fast-growing competitors, and small cells in biofilms may contribute to the formation and transmission of bioaerosols.

Mutation on lysX from Mycobacterium avium hominissuis impacts the host-pathogen interaction and virulence phenotype

The lysX gene from Mycobacterium avium hominissuis (MAH) is not only involved in cationic antimicrobial resistance but also regulates metabolic activity. An MAH lysX deficient mutant was shown to exhibit a metabolic shift at the extracellular state preadapting the bacteria to the conditions inside host-cells. It further showed stronger growth in human monocytes. In the present study, the LysX activity on host-pathogen interactions were analyzed. The lysX mutant from MAH proved to be more sensitive toward host-mediated stresses such as reactive oxygen species. Further, the lysX mutant exhibited increased inflammatory response in PBMC and multinucleated giant cell (MGC) formation in human macrophages during infection studies. Coincidentally, the lysX mutant strain revealed to be more reproductive in the Galleria mellonella infection model. Together, these data demonstrate that LysX plays a role in regulating the bacillary load in host organisms and the lack of lysX gene facilitates MAH adaptation to intracellular host-habitat, thereby suggesting an essential role of LysX in the modulation of host-pathogen interaction.

The rough colony morphotype of Mycobacterium avium exhibits high virulence in human macrophages and mice

Introduction. The incidence of Mycobacterium avium complex (MAC) pulmonary disease (MAC PD), a refractory chronic respiratory tract infection, is increasing worldwide. MAC has three predominant colony morphotypes: smooth opaque (SmO), smooth transparent (SmT) and rough (Rg).Aim. To determine whether colony morphotypes can predict the prognosis of MAC PD, we evaluated the virulence of SmO, SmT and Rg in mice and in human macrophages.Methodology. We compared the characteristics of mice and human macrophages infected with the SmO, SmT, or Rg morphotypes of M. avium subsp. hominissuis 104. C57BL/6 mice and human macrophages derived from peripheral mononuclear cells were used in these experiments.Results. In comparison to SmO- or SmT-infected mice, Rg-infected mice revealed severe pathologically confirmed pneumonia, increased lung weight and increased lung bacterial burden. Rg-infected macrophages revealed significant cytotoxicity, increased bacterial burden, secretion of proinflammatory cytokines (TNF-α and IL-6) and chemokines (CCL5 and CCL3), and formation of cell clusters. Rg formed larger bacterial aggregates than SmO and SmT. Cytotoxicity, bacterial burden and secretion of IL-6, CCL5 and CCL3 were induced strongly by Rg infection, and were decreased by disaggregation of the bacteria.Conclusion. M. avium Rg, which is associated with bacterial aggregation, has the highest virulence among the predominant colony morphotypes.

Integrated Quantitative Proteomics and Metabolome Profiling Reveal MSMEG_6171 Overexpression Perturbing Lipid Metabolism of Mycobacterium smegmatis Leading to Increased Vancomycin Resistance

In recent years, the treatment of tuberculosis is once again facing a severe situation because the existing antituberculosis drugs have become weaker and weaker with the emergence of drug-resistant Mycobacterium tuberculosis (Mtb). The studies of cell division and cell cycle-related factors in Mtb are particularly important for the development of new drugs with broad-spectrum effects. Mycobacterium smegmatis (Msm) has been used as a model organism to study the molecular, physiological, and drug-resistant mechanisms of Mtb. Bioinformatics analysis has predicted that MSMEG_6171 is a MinD-like protein of the septum site-determining protein family associated with cell division in Mycobacterium smegmatis. In our study, we use ultrastructural analysis, proteomics, metabolomics, and molecular biology techniques to comprehensively investigate the function of MSMEG_6171. Overexpression of MSMEG_6171 in Msm resulted in elongated cells, suggesting an important role of MSMEG_6171 in regulating cell wall morphology. The MSMEG_6171 overexpression could enhance the bacterial resistance to vancomycin, ethionamide, meropenem, and cefamandole. The MSMEG_6171 overexpression could alter the lipid metabolism of Msm to cause the changes on cellular biofilm property and function, which enhances bacterial resistance to antibiotics targeting cell wall synthesis. MSMEG_6171 could also induce the glyceride and phospholipid alteration in vivo to exhibit the pleiotropic phenotypes and various cellular responses. The results showed that amino acid R249 in MSMEG_6171 was a key site that can affect the level of bacterial drug resistance, suggesting that ATPase activity is required for function.

Natural products from thioester reductase containing biosynthetic pathways

Covering: up to 2018 Thioester reductase domains catalyze two- and four-electron reductions to release natural products following assembly on nonribosomal peptide synthetases, polyketide synthases, and their hybrid biosynthetic complexes. This reductive off-loading of a natural product yields an aldehyde or alcohol, can initiate the formation of a macrocyclic imine, and contributes to important intermediates in a variety of biosyntheses, including those for polyketide alkaloids and pyrrolobenzodiazepines. Compounds that arise from reductase-terminated biosynthetic gene clusters are often reactive and exhibit biological activity. Biomedically important examples include the cancer therapeutic Yondelis (ecteinascidin 743), peptide aldehydes that inspired the first therapeutic proteasome inhibitor bortezomib, and numerous synthetic derivatives and antibody drug conjugates of the pyrrolobenzodiazepines. Recent advances in microbial genomics, metabolomics, bioinformatics, and reactivity-based labeling have facilitated the detection of these compounds for targeted isolation. Herein, we summarize known natural products arising from this important category, highlighting their occurrence in Nature, biosyntheses, biological activities, and the technologies used for their detection and identification. Additionally, we review publicly available genomic data to highlight the remaining potential for novel reductively tailored compounds and drug leads from microorganisms. This thorough retrospective highlights various molecular families with especially privileged bioactivity while illuminating challenges and prospects toward accelerating the discovery of new, high value natural products.

Role of the Mycobacterium marinum ESX-1 Secretion System in Sliding Motility and Biofilm Formation

Mycobacterium marinum is a close relative of Mycobacterium tuberculosis that can cause systemic tuberculosis-like infections in ectotherms and skin infections in humans. Sliding motility correlates with biofilm formation and virulence in most bacteria. In this study, we used a sliding motility assay to screen 2,304 transposon mutants of M. marinum NTUH-M6885 and identified five transposon mutants with decreased sliding motility. Transposons that interrupted the type VII secretion system (T7SS) ESX-1-related genes, espE (mmar_5439), espF (mmar_5440), and eccA1 (mmar_5443), were present in 3 mutants. We performed reverse-transcription polymerase chain reaction to verify genes from mmar_5438 to mmar_5450, which were found to belong to a single transcriptional unit. Deletion mutants of espE, espF, espG (mmar_5441), and espH (mmar_5442) displayed significant attenuation regarding sliding motility and biofilm formation. M. marinum NTUH-M6885 possesses a functional ESX-1 secretion system. However, deletion of espG or espH resulted in slightly decreased secretion of EsxB (which is also known as CFP-10). Thus, the M. marinum ESX-1 secretion system mediates sliding motility and is crucial for biofilm formation. These data provide new insight into M. marinum biofilm formation.

Nonphotodynamic Roles of Methylene Blue: Display of Distinct Antimycobacterial and Anticandidal Mode of Actions

Significance of methylene blue (MB) in photodynamic therapy against microbes is well established. Previously, we have reported the antifungal potential of MB against Candida albicans. The present study attempts to identify additional antimicrobial effect of MB against another prevalent human pathogen, Mycobacterium tuberculosis (MTB). We explored that MB is efficiently inhibiting the growth of Mycobacterium at 15.62 μg/ml albeit in bacteriostatic manner similar to its fungistatic nature. We uncovered additional cell surface phenotypes (colony morphology and cell sedimentation rate) which were impaired only in Mycobacterium. Mechanistic insights revealed that MB causes energy dependent membrane perturbation in both C. albicans and Mycobacterium. We also confirmed that MB leads to enhanced reactive oxygen species generation in both organisms that could be reversed upon antioxidant supplementation; however, DNA damage could only be observed in Mycobacterium. We provided evidence that although biofilm formation was disrupted in both organisms, cell adherence to human epithelial cells was inhibited only in Mycobacterium. Lastly, RT-PCR results showed good correlation with the biochemical assay. Together, apart from the well-established role of MB in photodynamic therapy, this study provides insights into the distinct antimicrobial mode of actions in two significant human pathogens, Candida and Mycobacterium, which can be extrapolated to improve our understanding of finding novel therapeutic options.

Insights from the Genome Sequence of Mycobacterium lepraemurium: Massive Gene Decay and Reductive Evolution

Mycobacterium lepraemurium is the causative agent of murine leprosy, a chronic, granulomatous disease similar to human leprosy. Due to the similar clinical manifestations of human and murine leprosy and the difficulty of growing both bacilli axenically, Mycobacterium leprae and M. lepraemurium were once thought to be closely related, although it was later suggested that M. lepraemurium might be related to Mycobacterium avium. In this study, the complete genome of M. lepraemurium was sequenced using a combination of PacBio and Illumina sequencing. Phylogenomic analyses confirmed that M. lepraemurium is a distinct species within the M. avium complex (MAC). The M. lepraemurium genome is 4.05 Mb in length, which is considerably smaller than other MAC genomes, and it comprises 2,682 functional genes and 1,139 pseudogenes, which indicates that M. lepraemurium has undergone genome reduction. An error-prone repair homologue of the DNA polymerase III α-subunit was found to be nonfunctional in M. lepraemurium, which might contribute to pseudogene formation due to the accumulation of mutations in nonessential genes. M. lepraemurium has retained the functionality of several genes thought to influence virulence among members of the MAC.

Mycobacterium lepraemurium seems to be evolving toward a minimal set of genes required for an obligatory intracellular lifestyle within its host, a niche seldom adopted by most mycobacteria, as they are free-living. M. lepraemurium could be used as a model to elucidate functions of genes shared with other members of the MAC. Its reduced gene set can be exploited for studying the essentiality of genes in related pathogenic species, which might lead to discovery of common virulence factors or clarify host-pathogen interactions. M. lepraemurium can be cultivated in vitro only under specific conditions and even then with difficulty. Elucidating the metabolic (in)capabilities of M. lepraemurium will help develop suitable axenic media and facilitate genetic studies.

Mycobacteria Clumping Increase Their Capacity to Damage Macrophages

The rough morphotypes of non-tuberculous mycobacteria have been associated with the most severe illnesses in humans. This idea is consistent with the fact that Mycobacterium tuberculosis presents a stable rough morphotype. Unlike smooth morphotypes, the bacilli of rough morphotypes grow close together, leaving no spaces among them and forming large aggregates (clumps). Currently, the initial interaction of macrophages with clumps remains unclear. Thus, we infected J774 macrophages with bacterial suspensions of rough morphotypes of M. abscessus containing clumps and suspensions of smooth morphotypes, primarily containing isolated bacilli. Using confocal laser scanning microscopy and electron microscopy, we observed clumps of at least five rough-morphotype bacilli inside the phagocytic vesicles of macrophages at 3 h post-infection. These clumps grew within the phagocytic vesicles, killing 100% of the macrophages at 72 h post-infection, whereas the proliferation of macrophages infected with smooth morphotypes remained unaltered at 96 h post-infection. Thus, macrophages phagocytose large clumps, exceeding the bactericidal capacities of these cells. Furthermore, proinflammatory cytokines and granuloma-like structures were only produced by macrophages infected with rough morphotypes. Thus, the present study provides a foundation for further studies that consider mycobacterial clumps as virulence factors.

Sliding Motility, Biofilm Formation, and Glycopeptidolipid Production in Mycobacterium colombiense Strains

Mycobacterium colombiense is a novel member of the Mycobacterium avium complex, which produces respiratory and disseminated infections in immunosuppressed patients. Currently, the morphological and genetic bases underlying the phenotypic features of M. colombiense strains remain unknown. In the present study, we demonstrated that M. colombiense strains displaying smooth morphology show increased biofilm formation on hydrophobic surfaces and sliding on motility plates. Thin-layer chromatography experiments showed that M. colombiense strains displaying smooth colonies produce large amounts of glycolipids with a chromatographic behaviour similar to that of the glycopeptidolipids (GPLs) of M. avium. Conversely, we observed a natural rough variant of M. colombiense (57B strain) lacking pigmentation and exhibiting impaired sliding, biofilm formation, and GPL production. Bioinformatics analyses revealed a gene cluster that is likely involved in GPL biosynthesis in M. colombiense CECT 3035. RT-qPCR experiments showed that motile culture conditions activate the transcription of genes possibly involved in key enzymatic activities of GPL biosynthesis.

Pathogenesis and risk factors for nontuberculous mycobacterial lung disease

Nontuberculous mycobacteria (NTM) infections are broadly classified as skin and soft tissue infections, isolated lung disease, and visceral or disseminated disease. The degree of underlying immune abnormalities varies between each classification. Skin and soft tissue infections are usually the result of iatrogenic or accidental inoculation of NTM in otherwise normal hosts. Visceral and disseminated NTM disease invariably occurs in individuals with more severe immunosuppression. Although the focus of this article is to discuss the pathogenesis of NTM lung disease, the risk factors of visceral/disseminated NTM disease are also summarized, as they provide insights into host-defense mechanisms against these organisms.

Pathogen roid rage: cholesterol utilization by Mycobacterium tuberculosis

The ability of science and medicine to control the pathogen Mycobacterium tuberculosis (Mtb) requires an understanding of the complex host environment within which it resides. Pathological and biological evidence overwhelmingly demonstrate how the mammalian steroid cholesterol is present throughout the course of infection. Better understanding Mtb requires a more complete understanding of how it utilizes molecules like cholesterol in this environment to sustain the infection of the host. Cholesterol uptake, catabolism and broader utilization are important for maintenance of the pathogen in the host and it has been experimentally validated to contribute to virulence and pathogenesis. Cholesterol is catabolized by at least three distinct sub-pathways, two for the ring system and one for the side chain, yielding dozens of steroid intermediates with varying biochemical properties. Our ability to control this worldwide infectious agent requires a greater knowledge of how Mtb uses cholesterol to its advantage throughout the course of infection. Herein, the current state of knowledge of cholesterol metabolism by Mtb is reviewed from a biochemical perspective with a focus on the metabolic genes and pathways responsible for cholesterol steroid catabolism.