The carbohydrate- and lipid-containing cell wall of mycobacteria, phenolic glycolipids: structure and immunological properties.

Phenolic glycolipids were first discovered as cell-wall constituents of M. bovis, M. bovis BCG, M. marinum, and M. kansasii. Recently, such compounds were also isolated from M. leprae and have been shown to be specific-species serological markers. Moreover, they seem to be involved, in the case of lepromatous leprosy, in the stimulation of the suppressor T-cells. The functional activities of these phenolic glycolipids over the immune cells stimulation emphasized the role played by these molecules in the mycobacteria pathogenicity. Phenolic glycolipids have also been found in M. gastri and M. tuberculosis strain Canetti. From a structural point of view, these glycolipids contain the same aglycon moiety mainly assigned to phenolphthiocerol diester while the sugar part structure confers to some of these glycolipids their antigenic specificity. The search of immunoreactive glycolipids and their function analysis remain a challenge for chemists and immunologists for the understanding of the mycobacteria pathogenicity.

Analysis of dimycocerosates of glycosylphenolphthiocerols in the identification of some clinically significant mycobacteria.

Extracts of representative mycobacteria were examined by thin-layer chromatography for glycosylphenolphthiocerol dimycocerosates. The glycolipid typical of Mycobacterium bovis was also found in Mycobacterium africanum and Mycobacterium microti, but it was absent in Mycobacterium bovis AN 5. Mycobacterium gastri strains contained a glycolipid which was chromatographically similar to that in Mycobacterium kansasii. Representatives of Mycobacterium marinum produced a distinct glycolipid type, and one strain had major amounts of a more polar variant. The sugar moieties of purified lipids, including that from Mycobacterium leprae, were identified by thin-layer chromatography of methyl glycosides in acid methanolysates.

Quantitative comparison of the mycolic and fatty acid compositions of Mycobacterium leprae and Mycobacterium gordonae.

The mycolic and fatty acids of three samples each of Mycobacterium leprae and Mycobacterium gordonae were compared. Acids released by whole-organism alkaline hydrolysis were converted to 4-nitrobenzyl esters and mycolic acids were further derivatized to t-butyldimethylsilyl ethers. Thin-layer chromatography of the derivatized long-chain extracts showed that all three M. leprae preparations contained so-called alpha-mycolates and ketomycolates but that the M. gordonae samples had a methoxymycolate in addition to the above types. Silica gel normal-phase high-performance liquid chromatography of the total mycolic acid derivatives confirmed the lack of detectable amounts of methoxymycolates in M. leprae and reverse-phase chromatography of the individual mycolate types demonstrated the homogeneity of the chain lengths of the mycolic acids in each species. Non-hydroxylated fatty acid 4-nitrobenzyl esters were transformed to methyl esters and examined by gas chromatography. Tuberculostearic (10-methyloctadecanoic) acid was a major component of the lipids of all three M. leprae preparations but it was absent in one M. gordonae strain and a very minor component in the other representatives of this latter species. On the basis of fatty and mycolic acid compositions, therefore, a previously suggested close relationship between M. leprae and M. gordonae was not supported.

[Specific lipids from Mycobacterium ulcerans]. / Lipides spécifiques de Mycobacterium ulcerans.

The main lipids synthesized by Mycobacterium ulcerans are specific for the species. Three products were isolated by chromatography. Their structures were determined by means of spectrographic methods performed on the natural substances or on their split products. The most abundant products were phthiodiolone diphthioceranate and phenolphthiodiolone diphthioceranate . These structures have some analogies with those of phthiocerol dimycocerosate synthesized by M. tuberculosis and M. bovis, and with those of phenolphthiocerol mycocerosate synthesized by M. bovis. The reverse configuration of the polymethyl-branched-chain fatty acids isolated from the substances, according to their origin, remains to be pointed out. Little attention has generally been paid to the stereochemistry of such molecules. We verified that the branched-chain fatty acids found in diacyl phthiocerol and in the mycoside of M. leprae have the same configuration as in the analogous molecules isolated from M. tuberculosis or M. bovis, contrary to M. ulcerans. Another peculiarity of phenolphthiodiolone isolated from M. ulcerans is the occurrence of the phenol group in free form.

A novel phenolic glycolipid from Mycobacterium leprae possibly involved in immunogenicity and pathogenicity.

A phenolic glycolipid was obtained in high amounts (2% of dry weight) from Mycobacterium leprae isolated from infected armadillo liver. Infrared and nuclear magnetic resonance spectroscopy showed that it is closely related to "mycoside A" from Mycobacterium kansasii and is therefore a glycosylphenolic phthiocerol diester. The crucial difference between the two products is in the composition of the attached trisaccharide. Gas-liquid chromatography-mass spectroscopy showed that the product from M. kansasii is composed of 2,4-di-O-methylrhamnose, 2-O-methylrhamnose, and 2-O-methylfucose, whereas that from M. leprae contains 2,3-di-O-methylrhamnose, 3-O-methylrhamnose, and 3,6-di-O-methylglucose. The distinct composition of the oligosaccharide segment of the glycolipid from M. leprae may make it useful for the chemical and serological differentiation of this organism from other mycobacteria. Surprisingly large quantities (2.2 mg/g of dry liver) of the glycolipid were also found in infected liver residue freed of M. leprae, suggesting that it may be responsible for the electron-transparent "foam" surrounding the organism in infected lepromatous tissue.