COMPOSITION AND TOXICITY OF DIETHYL-ETHER SOLUBLE LIPIDS FROM NOCARDIA-ASTEROIDES GUH-2 AND NOCARDIA-ASTEROIDES 10905

Virulent Nocardia asteroides GUH-2 and avirulent N. asteroides 10905 c ontained 8.2% and 10.6% of diethyl ether soluble lipids (DESL) per dry cell mass, respectively. Intraperitoneal (i.p.) inoculation of 250,ug of DESL from GUH-2 dissolved in mineral oil was toxic to mice, result ing in weight loss and death of 100% of the animals (20/20) within 20 days. In contrast, DESL from 10905 had very little toxicity, and only one mouse (1/10) died within 30 days. Three fractions resulted from DE SL by silicic acid column chromatography: (1) neutral lipids and fatty acids (NFA); (2) glycolipids (GL); and (3) phospholipids (PL). Each f raction dissolved in mineral oil was inoculated into mice as described above. The NFA and PL were not toxic. GL from 10905 had low toxicity (30% of the animals died, 3/10) whereas GL from GUH-2 expressed high t oxicity (100% of the animals became cachetic and died, 10/10). GL from 10905 represented a minor component (0.6% of dry cell weight) whereas GL from GUH-2 was more prominent (1.5% of dry cell wt.). Approximatel y 95% of GL from GUH-2 had properties of an authentic trehalose-6,6'-d imycolate standard. Infrared spectrum of the major glycolipid (GUH-2 G L) had characteristic absorptions in the fingerprint region between 80 0 cm-1 and 1500 cm-1. Upon alkaline hydrolysis GUH-2 GL released 76% m ycolic acids in the C50 size range plus 24% trehalose. Molecular weigh t determination of the methyl ester derivatives of the mycolic acid mo iety by thermospray mass spectral analysis revealed the presence of th e following underivatized nocardomycolic acid species: (1) monounsatur ated C50:1' C52:1 and C54:1 mycolic acids; (2) diunsaturated C50:2, C5 2:2 and C54:2 mycolic acids, and (3) triunsaturated C54:3 and C56:3 MY COlic acids. GUH-2 GL assigned as trehalose dinocardomycolate dissolve d in mineral oil was very toxic to mice. These finding strongly sugges t a relationship between trehalose dinocardomycolate content in N. ast eroides and pathogenicity.