Glycobiology of the Mycobacterial Surface

Abstract

The genus Mycobacterium is composed of obligate aerobes that grow more slowly than most other bacteria, generation times between a few hours to several days, and includes Mycobacterium tuberculosis, the causative agent of tuberculosis. Of all the infectious diseases that have plagued man, tuberculosis probably has been responsible for the greatest morbidity and mortality. Even today, when the incidence of tuberculosis in the Western nations has markedly decreased, more people died from tuberculosis in 1995-about 3.1 million-than in any other year in history, according to the 1996 report of the World Health Organization (Moran, 1996). Almost 2 billion people (one third of the world's population) have been infected by M. tuberculosis, of whom 5-10% will develop the active disease. Although most tuberculous patients currently are living primarily in developing countries, tuberculosis is becoming a major health problem in industrialized coun-

Surface-exposed Glycopeptidolipids of Mycobacterium smegmatis Specifically Inhibit the Phagocytosis of Mycobacteria by Human Macrophages

“…Their one-dimensional (Fig. 8) and two-dimensional 1 H-NMR spectra were very similar to those of the previously characterized C-type GPLs (33) and confirmed the presence of i) phenylalaninyl, threoninyl, alaninyl, and alaninol residues, ii) deoxysugar units, iii) ␤-hydroxylated long-chain, iv) double bonds, and v) methoxyl groups in these compounds (35). Molecules in fractions S8, S13, and S20 were thereafter called GPLs I, II, and III, respectively (Fig.…”

“…The allo-threoninyl-linked sugar unit of non-servar-specific GPLs may be further glycosylated in some GPL-containing mycobacteria, such as M. avium (33,34). These discrete modifications confer to GPLs variable TLC patterns and antigenic properties (20,33,34). Detailed chemical analysis of the various purified GPLs that occur in M. smegmatis demonstrated the existence of a novel class of these molecules passed unnoticed in previous studies (Fig.…”

“…C-type GPLs are a family of species-specific lipids that typifies many non-tuberculous mycobacterial species (16,33). In particular, they have been identified on the surface of M. smegmatis and M. avium but not on M. tuberculosis or M. kansasii (32).…”

“…In all known C-type GPLs, the alaninol residue is substituted by a O-CH 3 -rhamnosyl or dirhamnosyl residue (33). In M. smegmatis, a di-O-acylated-6-deoxy-talosyl residue is linked to the allo-threoninyl residue.…”

“…These simplest forms are found in all GPL-containing mycobacterial species and, accordingly, are called non-servar-specific GPLs or apolar GPLs. The allo-threoninyl-linked sugar unit of non-servar-specific GPLs may be further glycosylated in some GPL-containing mycobacteria, such as M. avium (33,34). These discrete modifications confer to GPLs variable TLC patterns and antigenic properties (20,33,34).…”