Immunochemical Analysis of Mycoplasma Pneumoniae

Summary Lipids of Mycoplasma pneumoniae were fractionated by chromatography on columns of diethylaminoethylcellulose and silicic acid, and on thin layers of silica gel G. Hapten activity, measured in implement‐fixation tests with rabbit and with human antisera to M. pneumoniae , was found to be associated with four or more neutral glycolipids. These comprised digalactosyl‐ and trigalactosyldi‐ glycerides, a second dihexosyldiglyceride containing both glucose and golactose, and a trihexosyldiglyceride fraction containing both hexoses, which was probably a mixture of two or more substances. These glycolipids were labelled when the organisms were grown in the presence of radioactive glucose, glycerol or palmitate, but not when they were grown with labelled galactose. The label from glucose appeared in both the glucose and galactose moieties of these glycolipfds. A fraction, consisting mainly of alkali‐stable glycolipids. into which there was little or no incorporation of isotope during growth with labelled precursors, was also found to have hapten activity. Rabbit antisera to M. pneumoniae were found to cross‐react with glycolipids from other sources, including the ceramide lactoside of mammalian tissues (cytolipin H). Chloroform‐methanol extracts of M. pneumoniae contained large amounts of lecithin, which was not labelled during growth with the isotopic precursors used. The major phosphatide synthesized by the organisms was phosphatidylglycerol. This was accompanied by smaller amounts of another phosphatide, tentatively identified as a phosphatidyl monoglyceride, which fixed complement with Wassermann‐positive human sera. These two acidic phosphatides were found to be radioactive after the cells had been grown with labelled glycerol or palmitate.