Biochemical studies of bacterial sporulation and germination. X. Ribosomes and nucleic acids of vegetative cells and spores of Bacillus megaterium.

The ribosomal particles and nucleic acid components of Bacillus megaterium log phase cells and spores were isolated and compared. Analysis of the total RNA indicated that 23 S, 16 S, and 4 S components were present, in the same relative proportions in both cases. Soluble RNA was 19% of vegetative cell RNA and 21% of spore RNA. Particles sedimenting at values greater than 100 S and sensitive to pancreatic ribonuclease were present in lysates of both vegetative cells and spores. Although the spore particles were sr~all in size and quantity and were relatively unstable, they suggest the existence of polysomes and associated messenger RNA in spores. Ribosomes purified from either source were mainly 70 S and 100 S particles and were quantitatively dissociated into 50 S and 30 S subunits in each case. Isolation of RNA from purified ribosomes yielded 23 S and 16 S material in a ratio of about 2:l. Although thermal denaturation profiles of ribosomal RNA isolated from both sources were identical, spore ribosomes melted at a lower temperature than vegetative cell ribosomes, possibly because of the presence of nuclease. DNA isolated from either vegetative cells or spores had a buoyant density in CsCl of 1.698 g per cc, and no satellite DNA was evident. These results indicate that the ribosome and nucleic acid components of log phase cells and spores are similar in relative amounts and physicochemical properties.