Separation of C50–60 and C70–80 mycolic acid molecular species and their changes by growth temperatures in Mycobacterium phlei

Toriyama, Seiko; Yano, Ikuya; Masui, Masamiki; Kusunose, Masamichi; Kusunose, Emi

doi:10.1016/0014-5793(78)80063-5

Cited by 40 publications

(16 citation statements)

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“…The emergence of new mass peaks corresponding to the C 88 to C 92 chain length of mycolic acids (1328, 1356, and 1384) in the parental strain, but not in the mutants, clearly suggested the role of the mymA operon in the synthesis of these mycolic acids at acidic pH. Such modifications in the chain length of mycolic acids in mycobacteria on exposure to environmental stresses have been reported in several studies (2,31,33,63,64), emphasizing the requirement of the appropriate repertoire of mycolic acids to respond to environmental stresses. Further, the enhanced accumulation of C 24:0 /C 26:0 fatty acids in the mutant strains substantiates their role in the synthesis of mycolic acids by the mymA operon.…”

Section: Discussionmentioning

confidence: 57%

Requirement of themymAOperon for Appropriate Cell Wall Ultrastructure and Persistence ofMycobacterium tuberculosisin the Spleens of Guinea Pigs

et al. 2005

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We had recently reported that the mymA operon (Rv3083 to Rv3089) of Mycobacterium tuberculosis is regulated by AraC/XylS transcriptional regulator VirS (Rv3082c) and is important for the cell envelope of M. tuberculosis. In this study, we further show that a virS mutant (Mtb⌬virS) and a mymA mutant (Mtbmym::hyg) of M. tuberculosis exhibit reduced contents and altered composition of mycolic acids along with the accumulation of saturated C 24 and C 26 fatty acids compared to the parental strain. These mutants were markedly more susceptible to major antitubercular drugs at acidic pH and also showed increased sensitivity to detergent (sodium dodecyl sulfate) and to acidic stress than the parental strain. We show that disruption of virS and mymA genes impairs the ability of M. tuberculosis to survive in activated macrophages, but not in resting macrophages, suggesting the importance of the mymA operon in protecting the bacterium against harsher conditions. Infection of guinea pigs with Mtb⌬virS, Mtbmym::hyg, and the parental strain resulted in an ϳ800-fold-reduced bacillary load of the mutant strains compared with the parental strain in spleens, but not in the lungs, of animals at 20 weeks postinfection. Phenotypic traits were fully complemented upon reintroduction of the virS gene into Mtb⌬virS. These observations show the important role of the mymA operon in the pathogenesis of M. tuberculosis at later stages of the disease.Mycobacterium tuberculosis, the etiological agent of extremely serious human infections, is a highly successful intracellular pathogen because it can adapt itself to various hostile environments. The cell envelope of mycobacteria is known to play a major role in their virulence and resistance to hostile environments. Besides, interaction of the mycobacterial cell envelope with host cell receptors facilitates uptake of the bacterium and modulation of host immune responses (12). Mycobacterium tuberculosis has approximately 250 genes involved in its lipid metabolism, and the lipid contents of the pathogen contribute to 60% of the cell dry weight (10,12). A number of genes involved in the synthesis of essential components of the cell envelope for maintaining appropriate cell wall architecture of M. tuberculosis have been identified, and their requirement for the virulence of M. tuberculosis has been established, suggesting their importance as targets for the development of new antitubercular drugs (4,8,19,22,57). Genes responsible for the biosynthesis of oxygenated mycolic acids and cyclopropanated mycolic acids were shown to be important for the in vivo growth and persistence of M. tuberculosis (19,22,57). The gene cluster involved in the biosynthesis of major complex lipids phthiocerol and phenolphthiocerol dimycocerosates of M. tuberculosis have been shown to play an important role in its virulence (11). Induction of various genes involved in fatty acid metabolism in caseous granuloma (9) or human macrophages (20) or after exposure to sodium dodecyl sulfate (SDS) (37, 57) or acidic stress (21) su...

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Section: Discussionmentioning

confidence: 57%

Requirement of themymAOperon for Appropriate Cell Wall Ultrastructure and Persistence ofMycobacterium tuberculosisin the Spleens of Guinea Pigs

et al. 2005

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“…In the cell walls from organisms grown at 18, 30, 37 or 45°C, the highest thermal transitions occurred at 49.8, 60.3, 63.5, and 65.6°C, respectively. Earlier studies indeed showed that the composition of mycolates showed a significant change in M. smegmatis depending on growth temperature (24,25). An increase in the growth temperature from 20 to 45°C increased the chain length somewhat, so that the major ␣-mycolate species at these two temperatures were C 74 -76 and C 78 , respectively.…”

Section: Dsc Of Cell Walls Purified From M Smegmatis Grown At Differmentioning

confidence: 97%

Mycolic Acid Structure Determines the Fluidity of the Mycobacterial Cell Wall

Liu

Barry

Besra

et al. 1996

Journal of Biological Chemistry

255

227

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The low permeability of the mycobacterial cell wall is thought to contribute to the well known resistance of mycobacteria to antibiotics and chemotherapeutic agents. We have used differential scanning calorimetry to demonstrate that the high temperature phase transition observed in purified cell walls, usually in the 60 -70°C range, suggestive of a lipid environment of extremely low fluidity, can also be observed in whole organisms and in cell walls from which much of the free lipids was removed by extraction with Triton X-114. A survey of seven mycobacterial species demonstrated that this high temperature transition was a general property of these organisms. Cell walls isolated from two Corynebacterium species, which contain much shorter corynemycolic acids, displayed a much lower temperature transition, suggesting that the transition temperature was directly correlated to the length of mycolic acid. Methyl esters of mycolic acids were found to have a phase transition temperature that was linearly related to the amount of trans-mycolate. Both Mycobacterium avium and M. smegmatis responded to increasing growth temperature by increasing the proportion of trans-mycolate and displaying a correspondingly higher melting temperature. Whole cells of M. smegmatis grown at higher temperature allowed a less rapid influx of two lipophilic agents, norfloxacin and chenodeoxycholate. These results provide strong evidence that the nature of mycolic acid plays a crucial role in determining the fluidity and permeability of mycobacterial cell wall.Mycobacterial infections are the leading cause of death from infectious diseases (1). There are approximately 1 billion people presently infected with Mycobacterium tuberculosis. Leprosy, caused by M. leprae, affects 10 -12 million people (1). "Atypical mycobacteria," such as M. avium, M. intracellulare, M. xenopi, M. kansasii, M. chelonae, and M. fortuitum, cause opportunistic infections among AIDS patients. A major problem with the infections caused by mycobacteria is their intrinsic resistance to most general purpose antibiotics (1, 2). This problem is compounded by the emergence of multidrug-resistant strains of M. tuberculosis (3, 4).The intrinsic drug resistance of mycobacteria has been attributed, at least in part, to the low permeability of the cell wall (2). The influx of small, hydrophilic agents, which are likely to traverse the cell wall through porin channels (5, 6), is extremely slow (7), presumably because the cell wall contains only a small number of low specific activity porin molecules. On the other hand, mycobacterial cell walls are extremely rich in lipids. Lipophilic and amphiphilic agents may therefore be expected to cross the cell wall through its lipid domain, yet most mycobacteria exhibit high levels of intrinsic resistance even to such agents. We are therefore trying to understand how the lipid domain of the mycobacterial cell wall can serve as an effective permeability barrier by studying the physical organization of the cell wall lipids. The cell wall of myco...

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“…Several mycobacterial species, including M. smegmatis (22,24,26), have been shown to respond to changing growth temperatures by adjusting the proportion of lipids found in the trans-configuration. These alterations in lipid structure are not in the plasma membrane lipids but rather in the mycolic acids, as would be expected because the cell wall represents the major permeability barrier in the mycobacteria.…”

Section: Discussionmentioning

confidence: 99%

“…In general, cyclopropanated mycolic acids are considered to be a minor component of the cell wall in this species. Some Corynebacterineae, including M. smegmatis (22), have also been reported to alter their mycolic acid profile in response to changes in culture conditions like growth temperature (23)(24)(25)(26)(27). Thus, in M. smegmatis, the relative amounts and chain length of the different subclasses of mycolic acids are modified according to the growth temperatures (22).…”

mentioning

confidence: 99%

Temperature-dependent Regulation of Mycolic Acid Cyclopropanation in Saprophytic Mycobacteria

Alibaud

Alahari

Trivelli

et al. 2010

Journal of Biological Chemistry

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The cell envelope is a crucial determinant of virulence and drug resistance in Mycobacterium tuberculosis. Several features of pathogenesis and immunomodulation of host responses are attributable to the structural diversity in cell wall lipids, particularly in the mycolic acids. Structural modification of the ␣-mycolic acid by introduction of cyclopropane rings as catalyzed by the methyltransferase, PcaA, is essential for a lethal, persistent infection and the cording phenotype in M. tuberculosis. Here, we demonstrate the presence of cyclopropanated cell wall mycolates in the nonpathogenic strain Mycobacterium smegmatis and identify MSMEG_1351 as a gene encoding a PcaA homologue. Interestingly, ␣-mycolic acid cyclopropanation was inducible in cultures grown at 25°C. The growth temperature modulation of the cyclopropanating activity was determined by high resolution magic angle spinning NMR analyses on whole cells. In parallel, quantitative reverse transcription-PCR analysis showed that MSMEG_1351 gene expression is up-regulated at 25°C compared with 37°C. An MSMEG_1351 knock-out strain of M. smegmatis, generated by recombineering, exhibited a deficiency in cyclopropanation of ␣-mycolates. The functional equivalence of PcaA and MSMEG_1351 was established by cross-complementation in the MSMEG_1351 knock-out mutant and also in a ⌬pcaA strain of Mycobacterium bovis BCG. Overexpression of MSMEG_1351 restored the wild-type mycolic acid profile and the cording phenotype in BCG. Although the biological significance of mycolic acid cyclopropanation in nonpathogenic mycobacteria remains unclear, it likely represents a mechanism of adaptation of cell wall structure and composition to cope with environmental factors.Mycolic acids are major components of the hydrophobic cell wall of Corynebacterineae (1-4). These ␣-branched ␤-hydroxylated long chain fatty acids are covalently linked to the arabinogalactan layer that is attached to the peptidoglycan backbone and are also present as extractable lipids conjugated with sugars such as trehalose, forming trehalose dimycolate (4). Mycolic acids from mycobacteria possess a long main carbon chain called meromycolate, which in its nascent form is interrupted by double bonds at two specific sites called the proximal (closer to the ␤-hydroxy) and the distal positions. Chemical modifications of these double bonds give rise to different types of mycolic acids, depending on the nature of the chemical groups introduced. Mycobacterium tuberculosis carries the following three types of mycolic acids: ␣-subtypes, containing two cis-cyclopropane rings, and two oxygenated subtypes, harboring methoxy and keto functions on the distal position, with a cis-or trans-cyclopropane ring on the proximal site (1, 3). These chemical modifications are performed by a group of S-adenosylmethionine (AdoMet) 3 -dependent methyltransferases (3). These enzymes share extensive sequence similarity, but genetic studies have revealed the distinct functional characteristics of each in the biosynthesis of mycolic acids....

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Separation of C_50–60 and C_70–80 mycolic acid molecular species and their changes by growth temperatures in Mycobacterium phlei

Cited by 40 publications

References 13 publications

Requirement of themymAOperon for Appropriate Cell Wall Ultrastructure and Persistence ofMycobacterium tuberculosisin the Spleens of Guinea Pigs

Requirement of themymAOperon for Appropriate Cell Wall Ultrastructure and Persistence ofMycobacterium tuberculosisin the Spleens of Guinea Pigs

Mycolic Acid Structure Determines the Fluidity of the Mycobacterial Cell Wall

Temperature-dependent Regulation of Mycolic Acid Cyclopropanation in Saprophytic Mycobacteria

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