Time course dependent changes in contents and physical properties of glycolipid species in Rhodococcus rhodochrous.

The yield of trehalose dimycolate (TDM), the major glycolipid species elaborated by Rhodococcus rhodochrous, a producer of approx. C40-mycolic acid, was not constant in cells cultured for different periods of time. From cells collected at 24, 36, 72, 144 and 172 h of cultivation the following percentages of TDM in diethyl ether soluble lipids (DESL) were found: 10.8%, 23.4%, 10.0%, 9.0% and 5.0%, respectively. In turn, the cellular content accounted for approx. 0.6%, 1.2%, 0.9%, 0.6% and 0.2%, respectively. On the other hand, the yield of galactose monomycolate (GalMM), a minor glycolipid species maintained at approx. 3.4% in DESL during the different periods of time examined; this value represented about 0.3% of the cellular content. The melting temperatures of TDMs fell between 37 degrees C to approximately 97 degrees C with the lowest value from cells grown for 36 h, whereas the melting temperatures of the GalMMs were in a narrow range between 56 degrees C and 64 degrees C. The methyl ester derivatives of the constituent fatty acid moieties of DTMs and GalMMs migrated on thin layer chromatography like methyl esters of C40-C46 mycolic acids, therefore faster than methyl esters of C28-C34 mycolic acids but slower than methyl esters of C50-C56 mycolic acids. Further analysis of the products of pyrolysis of the methyl ester derivatives of the fatty acid moiety released from TDM after alkaline hydrolysis was carried out using gas chromatography combined mass spectrometry.(ABSTRACT TRUNCATED AT 250 WORDS)

Composition and toxicity of lipids from Rhodococcus rhodochrous grown on medium containing galactose, glucose or mannose.

Rhodococcus rhodochrous, a producer of mycolic acid of approx. C40, exhibited a higher cellular mass yield when grown on glucose than when grown on galactose or mannose. The cellular content of the diethyl ether-soluble lipids in microorganisms cultivated on glucose or mannose varied with the incubation time, while that of microorganisms grown on galactose remained constant. The lipids extracts from cells cultivated on different hexoses and collected at the exponential phase of growth were more toxigenic; this property was related in general to the content of glycolipid. On the other hand, cells cultivated on galactose or mannose had a higher quantity of glycolipid in the exponential phase, while the glycolipid content of those grown on glucose remained approximately constant. Amongst the components of the lipid extract, the glycolipid fraction was the sole fraction bearing toxic property. Neutral plus fatty acids and phospholipids displayed no similar characteristic.