Separation of Protein Synthesis in Meningopneumonitis Agent from That in L Cells by Differential Susceptibility to Cycloheximide

Cycloheximide had no effect on multiplication of the meningopneumonitis agent in L cells in concentrations which eliminated over 90% of the protein synthesis in the host cells. Infected L cells treated with cycloheximide, however, incorporated labeled amino acids into the trichloroacetic acid-insoluble fraction. This incorporation was attributed to the biosynthetic activity of the meningopneumonitis agent. Synthesis of meningopneumonitis protein was abolished by chloramphenicol and chlortetracycline, inhibitors of bacterial protein synthesis, at concentrations which did not inhibit protein synthesis in L cells. Protein synthesis in the meningopneumonitis agent was sustained at a high rate when the host cells remained viable and declined as the L cells died. Overall host protein synthesis was not inhibited by multiplication of the meningopneumonitis agent.