The structure of the mycobacterial cell envelope is not yet understood

Draper, P.

doi:10.1016/0923-2508(91)90113-o

Cited by 9 publications

(5 citation statements)

References 14 publications

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“…Similarly, some tubercle bacilli, notably the Canetti and Canetti-like strains, synthesize large amounts of PGLs (12,14,19), whereas other virulent strains contain only traces, if any at all, of these molecules (11,12,51). These observations suggested that PGLs and GPLs are not the major components of the mycobacterial capsule and that M. leprae and M. lepraemurium are anomalous in producing such very large amounts of lipids (22).…”

mentioning

confidence: 84%

Identification of the surface-exposed lipids on the cell envelopes of Mycobacterium tuberculosis and other mycobacterial species

et al. 1996

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The surface-exposed lipids of Mycobacterium tuberculosis, Mycobacterium avium, Mycobacterium kansasii, Mycobacterium gastri, Mycobacterium smegmatis, and Mycobacterium aurum were isolated by gentle mechanical treatment of cells with glass beads. Analysis of the exposed lipids demonstrated a selective location of classes of ubiquitous lipids on the surfaces of mycobacteria. While phosphatidylethanolamine and phosphatidylinositol mannosides were exposed in all the species examined, dimycoloyl trehalose (''cord factor'') was identified in the surface components of M. aurum only. Furthermore, monomycoloyl trehaloses and triacylglycerides were identified in the surface-exposed lipids of M. avium and M. smegmatis but not in those of the other mycobacterial species examined. The species-and type-species specific lipids were present on the mycobacterial cell surface: phenolic glycolipids, dimycocerosates of phthiocerols, and lipooligosaccharides were identified in the surface-exposed materials of M. tuberculosis (Canetti), M. kansasii, and M. gastri, whereas glycopeptidolipids were identified in the outermost lipid constituents of M. avium and M. smegmatis. This difference in the surface exposure of lipids of various mycobacterial species may reflect differences in their cell envelope organizations. Brief treatments of M. tuberculosis with Tween 80 prior to the use of glass beads led to erosion of regions of the capsule to expose gradually both cord factor and other lipids on the cell surface of the tubercle bacillus, demonstrating that the latter lipids are buried more deeply in the cell envelope and leading to the proposal of a scheme for the location of the capsular lipids of the tubercle bacillus.

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mentioning

confidence: 84%

Identification of the surface-exposed lipids on the cell envelopes of Mycobacterium tuberculosis and other mycobacterial species

et al. 1996

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“…Similarly, during freeze-substitution, the majority of radiolabel was detected in the acetone washes. The dehydration stage of conventional embedding tends to distort the mycobacterial envelope through the removal of water from polar wall polymers such as PG and arabinogalactan (6). If a proportion of these structures is solubilized and extracted during processing, it is possible that mycolic acids, which are covalently bound to the PG-arabinogalactan complex, will also be removed.…”

Section: Discussionmentioning

confidence: 99%

Reevaluation of envelope profiles and cytoplasmic ultrastructure of mycobacteria processed by conventional embedding and freeze-substitution protocols

1992

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The cell envelope architectures and cytoplasmic structures of Mycobactenium aurum CIPT 1210005, M. fortuitum, M. phlei 425, and M. thermoresistible ATCC 19527 were compared by conventional embedding and freeze-substitution methods. To ascertain the integrity of cells during each stage of the processing regimens, [1-_4Cjacetate was incorporated into the mycolic acids of mycobacterial walls, and the extraction of labeled mycolic acids was monitored by liquid scintillation counting. Radiolabeled mycolic acids were extracted by both processing methods; however, freeze-substitution resulted in the extraction of markedly less radiolabel. During conventional processing of cells, most of the radiolabel was extracted during the dehydration stage, whereas postsubstitution washes in acetone yielded the greatest loss of radiolabel during freeze-substitution. Conventional embedding frequently produced cells with condensed fibrous nucleoids and occasional mesosomes. Their cell walls were relatively thick (-25 nm) but lacked substance. Freeze-substituted cells appeared more robust, with well-dispersed nucleoids and ribosomes. The walls of all species were much thinner than those of their conventionally processed counterparts, but these stained well, which was an indication of more wall substance; the fabric of these walls, in particular the plasma membrane, appeared highly condensed and tightly apposed to the peptidoglycan. Some species possessed a thick, irregular outer layer that was readily visualized in the absence of exogenous stabilizing agents by freeze-substitution. Since freeze-substituted mycobacteria retained a greater percentage of mycolic acids in their walls, and probably other labile wall and cytoplasmic constituents, we believe that freeze-substitution provides a more accurate image of structural organization in mycobacteria than that achieved by conventional procedures.Tuberculosis remains a major health problem for humans, particularly in developing countries, with an estimated 8 million cases and 3 million deaths per year worldwide (7). In the United States, more than 22,000 new cases are being reported annually in particular populations. The epidemiology of tuberculosis has undergone a profound transition in recent years (21). An increase in the incidence of infection due to human immunodeficiency virus has resulted in a rise in the number of both typical and atypical mycobacterial infections. The Mycobacterium avium complex and M. kansasii are the most frequently encountered etiologic agents of atypical mycobacterial infections associated with AIDS (21); however, M. xenopi, M. fortuitum, and M. chelonae have also been reported previously (21).The molecular and structural compositions of the mycobacterial cell wall must play a significant role in its mechanisms of pathogenicity (18,22,23). Moreover, the intricate physical relationships among the diverse macromolecules within the wall appear to be responsible for properties such as drug resistance (4), acid fastness (1), hydrophobic interactions (25), and th...

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“…comprises other lipids, e.g. trehalose 6,6-dimycolate (TDM), lipoarabinomannan (LAM), phthiocerol dimycocerosates (PDIMs), phenolic glycolipids (PGLs) (Draper 1991; Daffé and Draper 1997; Smith 2003; Onwueme et al. 2005).…”

Section: Etiological Agent and Ecologymentioning

confidence: 99%

Mycobacterium marinum infection in fish and man: epidemiology, pathophysiology and management; a review

Hashish

Merwad

Elgaml

et al. 2018

Veterinary Quarterly

149

133

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Mycobacterium marinum is an opportunistic pathogen inducing infection in fresh and marine water fish. This pathogen causes necrotizing granuloma like tuberculosis, morbidity and mortality in fish. The cell wall-associated lipid phthiocerol dimycocerosates, phenolic glycolipids and ESAT-6 secretion system 1 (ESX-1) are the conserved virulence determinant of the organism. Human infections with Mycobacterium marinum hypothetically are classified into four clinical categories (type I-type IV) and have been associated with the exposure of damaged skin to polluted water from fish pools or contacting objects contaminated with infected fish. Fish mycobacteriosis is clinically manifested and characterized in man by purple painless nodules, liable to develop into superficial crusting ulceration with scar formation. Early laboratory diagnosis of M. marinum including histopathology, culture and PCR is essential and critical as the clinical response to antibiotics requires months to be attained. The pathogenicity and virulence determinants of M. marinum need to be thoroughly and comprehensively investigated and understood. In spite of accumulating information on this pathogen, the different relevant data should be compared, connected and globally compiled. This article is reviewing the epidemiology, virulence factors, diagnosis and disease management in fish while casting light on the potential associated public health hazards.

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The structure of the mycobacterial cell envelope is not yet understood

Cited by 9 publications

References 14 publications

Identification of the surface-exposed lipids on the cell envelopes of Mycobacterium tuberculosis and other mycobacterial species

Identification of the surface-exposed lipids on the cell envelopes of Mycobacterium tuberculosis and other mycobacterial species

Reevaluation of envelope profiles and cytoplasmic ultrastructure of mycobacteria processed by conventional embedding and freeze-substitution protocols

Mycobacterium marinum infection in fish and man: epidemiology, pathophysiology and management; a review

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