Membrane synthesis in Bacillus subtilis: I. Isolation and properties of strains bearing mutations in glycerol metabolism

Abstract

An experimental system for the study of membrane synthesis was constructed with mutant strains of Bacillus subtilis. Mutants were selected for glycerol auxotrophy and the inability to use glycerol as a source of carbon. Cells containing both mutations incorporated glycerol almost entirely into lipid. When cells were deprived of glycerol under otherwise normal growth conditions, the following results were obtained. The deprived cells underwent one slow division and remained viable for at least four hours. Net phospholipid synthesis stopped immediately, fatty acid synthesis was reduced to about 25% of the supplemented control, protein and DNA synthesis continued for about 90 minutes and net RNA synthesis ceased after about 30 minutes. Messenger RNA synthesis continued during the period in which net RNA synthesis was stopped, as indicated by continued protein synthesis and the inducibility of several enzymes. DNA synthesis did not stop at the end of a round of replication. Cell wall synthesis continued at the same rate as protein synthesis. The incorporation of labeled amino acids into membrane protein continued in the absence of lipid synthesis, indicating that a close co-ordination of membrane protein and lipid synthesis does not occur.