Peptidoglycolipid nature of the superficial cell wall sheath of smooth-colony-forming mycobacteria

Abstract

The most superficial cell wall layer present in smooth-colony-forming mycobacteria was isolated from serovar 20 of the Mycobacterium avium-Mycobacterium intracellulare-Mycobacterium scrofulaceum (MAIS) serocomplex and examined chemically and by electron microscopy. Most (70 to 80%) of the fibrillar material consisted of an array of serologically active, acetylated C-myosidic peptidoglycoplipids with the basic structure (formula, see text) but in which the location of acetyl groups and the arrangement of monosaccharides have not been defined. Apparently, all serovars within the MAIS complex are characterized by structurally related superficies in which the monoglycosyl-lipopeptide portion is invariable but the oligosaccharide attachment is peculiar to each serovar. These unique inert structures may be an important factor in shielding the pathogen within phagolysosomes from lysosomal enzymes.

Structural determination of glycopeptidolipids of Mycobacterium smegmatis by high‐resolution multiple‐stage linear ion‐trap mass spectrometry with electrospray ionization

“…[6] The antigenic polar GPL (serovar specific) has been associated with the change in colony morphology among natural isolates of M. avium. [7] GPLs also play important roles in biofilm formation, cell invasion and immune modulation; and variations in GPL structure, for example, structural modifications of the carbohydrate moieties, may affect the pathogenicity of M. avium complex and other GPL-expressing mycobacteria. [8] The immunomodulation aspects of M. avium pathogenesis and the role of GPLs as virulence factors have been recently reviewed.…”

Mycobacterium avium rough-to-smooth colony conversion resulting from growth in Tween 80 without presence of type-specific glycopeptidolipid antigens

“…Results of this study demonstrate that M. at,ium colonial morphology can be altered by the composition of the medium in which the organisms are grown, without alterations in at least one major group of surface-associated antigens, the GPL [4,5]. It has been reported [1] and confirmed [3] that the rough-colony variant of M. at,iurn completely lacks the ability to synthesize the GPL and the colonies it produces are of a distinct rough texture.…”

“…For this study, the rough-colony variant dcrived from a smooth-colony parent strain of M. arium complex serotype 20 was used [1]. This rough-colony variant is a stable mutant that lacks the ability to synthesize the serotype-specific GPL antigens [1,3] that are a major component of the outer L1 layer [4,5]. Mycobacterial cultures were cultivated in Middlebrook 7H9 (Difco) supplemented with 0.2% glycerol and 10% oleic acid albumin dextrose (OADC) (Difco).…”

“…Lipids were extracted from lyophilized mycobacteria with chloroform-methanol (2:1) and examined by thin-layer chromatography (TLC) using chloroform-methanol-water (60 : 12 : 1.0), Solvent A, and chloroform-methanol (11 : 1), Solvent B [1,5,6]. Lipids were detected by spraying TLC plates with an orcinol-sulphuric acid spray reagent followed by heating [4]. For analysis of radiolabeled lipids, distribution of radioactivity was determined by scraping cm sections of TLC plates into vials containing EcoLite (WestChem) scintillation fluid and counting in a scintillation spectrometer [6,7].…”

“…However, this colonial morphological change was not accompanied by a concomitant synthesis of GPL in the rough variant. A likely explanation for this is that the GPL, which are polar lipids [4], contribute to thc smooth-colony morphology by decreasing the hydrophobicity of the mycobacterial cell. Likewise, growth of the rough variant in the presence of a detergent such as Tween 80 can cause the same conversion, probably by a similar mechanism, i.e.…”