TREHALOSE-CONTAINING LIPOOLIGOSACCHARIDES OF MYCOBACTERIUM-GORDONAE -PRESENCE OF A MONO-O-METHYLTETRA-O-ACYLTREHALOSE CORE AND BRANCHING IN THE OLIGOSACCHARIDE BACKBONE

Past evidence has indicated that Mycobacterium gordonae, as isolated f rom soil and as an occasional opportunistic pathogen, exists as a sero complex. We now demonstrate that the basis of seroreactivity and diver sity is a novel series of alkali-labile, trehalose-containing lipoolig osaccharides (LOS). The structures from two strains were established b y per-O-methylation, partial acid hydrolysis, infrared and high-field NMR spectroscopy, electron-impact MS, and fast atom bombardment/mass s pectrometry of the native lipooligosaccharides and hydrolysis products . The structure of the major lipooligosaccharide, LOS-I, of M. gordona e strain 989 was defined as cp-(1-->3)-beta-D-Glcp-(1-->3)-2-OCH3-alph a-L-Rhap -D-Glcp-(1<->1)-2,3,4,6-tetra-O-acyl-alpha-D-Glcp, which was further glycosylated at C-3 of the terminal 2-O-CH3-4-O-CH3CO-alpha-L- Fucp by an incompletely defined N-acyl derivative of 4-amino-4,6-dideo xy-2,3-di-O-CH3-Galp. The structure of the major lipooligosaccharide, LOS-I, of a second strain of M. gordonae (strain 990) was defined as p ha-L-Rhap-(1-3)-[beta-D-Xylp-(1-2)-]-alpha-L-Rhap -D-Glcp-(1<->1)-2,3, 4,6-tetra-O-acyl-alpha-D-Glcp. The other minor LOSs from both strains were also defined. Both families of LOSs from the two strains contain a novel mono-6'-O-CH3-2,3,4,6-tetra-O-acyltrehalose unit, representing the first example of such a unit among the LOSs isolated to date from mycobacteria. Also, the more polar antigenic products, LOS-I, -II', - II'', and -III from M. gordonae 989 and LOS-I, -II, and -II' from M. g ordonae 990, are characterized by branching of the oligosaccharide bac kbone, the first instance of sugar branching in these products. In the case of LOS-I and -III from M. gordonae 989, the branch consists of a terminal (t)-beta-D-Xylp unit, whereas in LOS-II' and -II'', they are (t)-3-O-CH3-beta-D-Xylp and (t)-alpha-D-Araf, respectively. Similarly , the more polar antigenic glycolipids of M. gordonae 990 are characte rized by branching in the oligosaccharide backbone, a single terminal beta-D-Xylp residue in the case of LOS-I and LOS-II', and an alpha-D-A raf unit in LOS-II''. In some members of the LOS family, the unique br anching of the oligosaccharide backbone was absent. The LOSs reacted s trongly with antiserum raised against the homologous strain and only w eakly against that to the heterologous strain, demonstrating that M. g ordonae, like the Mycobacterium avium complex, is a serocomplex, but b ased on the trehalose-containing LOSs rather than the glycopeptidolipi ds.