Mycobacteria mycosides

As concerns the chemistry of these glycolipids, they contain either an eater linkage between the sugar moiety and the lipid moiety, as in cord factor and in wax D of Mycobacteria, or they are glycosides of phenolic alcohols (as in mycoside B) or of inositol (as in the phosphoglycolipids), or they can be linked to the carboxyl group of D-alanine (as in mycoside C). 

Mycosides Smith et al, (I960) reported mycosides which are the glycolipids and peptidoglycolipids type specific of mycobacteria. McLennan et al. (1961) ascertained that they have in common the particular terminal saccharide groups essentially containing rhamnoses... 

In addition to the wall-bound mycolic acids three other important lipids are loosely associated with the murein layer. The st of these is the cord factor , so called since it was associated with the formation of cords , parallel rows forming characteristic serpentine strands demonstrable when smears of liquid grown cultures of mycobacteria are examined under the microscope. The cord factor of M. tuberculosis can be readily extracted from viable bacteria with organic solvents and identified as trehalose-6,6 -dimycolate. The mycosides constitute the second group of readily extractable lipids, gycosidically linked to the para position of a phenol... 

Systematic examination of lipid extracts from Mycobacterium avium by infrared spectroscopy showed the presence of compounds exhibiting absorption bands at about 1235 cm which was attributed to acetyl ester groups (175), The substances responsible for this absorption were later isolated and as a group received the name of mycoside C. They were found in mycobacteria of the MAIS group Mycobacterium avium, M. intracellulare, M. scrofulaceum) and also in M. smegmatis, M. fortuitum, M. chelonae and some related species 176). 

As might be expected, the D-amino acids required for the biosynthesis of mycoside C are produced by mycobacteria from the L-amino acids. An alanine reductase able to reduce L-alanine to L-alaninol was detected in a cell-free preparation of M. avium 192). 

The production of mycosides C by a given species of mycobacteria cannot be used for taxonomic purposes since mutants occur that are devoid of mycoside C. In particular it has been observed that when... 

The polar mycosides C isolated from mycobacteria serovar 14 and 25 contained an unusual amino sugar which had been isolated previously from the lipooligosaccharides of M. kansasii and called kansosamine. Its... 

As the polar mycosides C behave as antigens they must be located in the outer layers of the mycobacterial cell. In fact their external location was demonstrated in M. intracellulare by the use of ferritin-labelled antibodies 214). It has long been known that mycobacteria of the MAIS complex are surrounded by an electron-transparent zone when ultra-thin sections of infected host tissues are examined under the electron microscope. This zone is essentially composed of parallel fibrils wrapped longitudinally around the bacterium. This material was isolated by the use of urea density gradients and analyzed chemically. The three amino acids characteristic of mycosides C and alaninol as well as 6-deoxytalose were identified 194). This material consisted mainly of a mixture of polar and apolar mycosides C, in a ratio about 7 3 (275). 

It was observed that o-, p- and m-monofluoro-DL-phenylalanine caused 80-90% inhibition of mycoside C biosynthesis in a strain of M. avium. Ultrastructural observation of the bacteria treated with the meta isomer showed profound alterations in the outer wall layer (277). In the course of a study on the multiplication and intracellular survival of M. avium inside macrophages, comparisons of smooth and rough variants (both producing mycosides C) and a mutant unable to synthesize mycoside C led to the conclusion that the mycosides C were not primary factors involved in the survival of mycobacteria inside macrophages 218). 

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