Spores of microorganisms

A pulse incorporation of radioactive precursors into the cells was used in studying the rate of RNA and protein synthesis during postgerminative development of spores ofBacillus cereus. It was found that the extractable pool of the spores can be enriched by these precursors during swelling and preelongation. During this period of differentiation of a spore to a primary cell,¹⁴C-uracil and to a smaller extent¹⁴C-adenine are more rapidly used for RNA synthesis. Labelled¹⁴C-leucine and³⁶S-methionine are found mostly in the extractable fraction of the cells. However, their rate of incorporation into proteins is not higher. Differences in utilization of precursors for the synthesis of macromolecules are apparently caused by different availability for the metabolic pool of the cell. Of the precursors tested¹⁴C-uracil seems to be selectively incorporated into RNA with a higher rate. This can be explained by a selective permeability into metabolic pool or by an increased need of uracil during preelongation period.