Lipid composition of leprosy-derived corynebacteria, a distinct group of corynebacteria, and of a reference Corynebacterium.

Abstract

Leprosy-derived corynebacteria (LDC) are diphtheroid organisms isolated from leprosy patients and previously characterized by DNA and cell wall analysis. Three groups of LDC components of taxonomic value, glycolipids, and phospholipids and cell-wall-bound lipids were analyzed in comparison with those of a reference strain C. hoffmannii (CH). The main CH glycolipid, "cord factor" (trehalose dimycolate), was missing from LDC. Among phospholipids, phosphatidylinositol and phosphatidylglycerol had lowered proportions in LDC, as compared to CH, whereas phosphatidylethanolamine and cardiolipin were absent from both microorganisms. Bound lipids in acidic extracts of delipidated LDC yielded arabinose corynomycolate in lesser quantity with respect to CH. Alkaline hydrolysis of whole cells released fatty acids and mycolic acids, which were analyzed by gas chromatography/mass spectrometry. Reference CH, grown in the absence of serum, yielded C16:0 and C18:1 (major) and C18:0 (minor) fatty acids, as well as C32, C34, and C36 corynomycolic acids. All these components, particularly mycolates, had lowered proportions when this organism was grown in the presence of serum. Dominant LDC components were, in addition to C16:0, C18:0, and CI8:u fatty acids, cholesterol from serum. Very low concentrations of corynomycolic acids with a high degree of unsaturation were found in these organisms, suggesting a dependence of lipid metabolism on growth conditions. The presence in LDC of tuberculostearic acid (C19r:0), a mycobacterial component found in some pathogenic corynebacteria, was carefully explored: Traces of C19r:0 were found in LDC 19 grown in the presence of delipidated serum, but not in LDC 15 nor in C. hoffmannii. Present data, in conjunction with previous studies on DNA and mycolic acids, disclose basic differences in the composition of LDC and conventional corynebacteria.