The duplication of bacterial chromatin; interpretations of some cytological and chemical studies of the germinating spores of Bacillus cereus and Bacillus megaterium.

In a separate paper, the changes in the P fractions of bacterial spores (luring geimination weere correlated with the morphological changes which took place at the same time. Germination has heen defined as the over-all period, some 50 to 60 min, extendling from the resting state of the "mononucleate" spore to the vegetative or "binucleate" cell. Thick suspensions (109 spores/ml) of synchronously growing spores, suitable for chemical analysis, were obtained bv heat activation and adjustment of the spore concentration to the medium. It was observed that during germination the basophilic nuclear material (chiromatin) of the spore and the amount of polymerized desoxyribonucleic acid increased simultaneously and continuously. The desoxvribonucleic acid had doubled only when the growing chromatin had sepaiated into two structures, each of which was similar in size an(l aIIangement to the single chroimiatin stIucture seen during the initial stage of germination (Fitz-James, 1954 unpublished results). However, recent histochemical studies of cell division in higher foims have indicatedl that in a typical mitosis the uptake of phosphorus into the desoxvribonucleic acid (Taylor, 1953) andl the doubling of the desoxyribonucleic acid ocCur' well before the separation processes of mletaphase and anaphase (Pasteels and Lison, 1950; Swift, 1950; Fautrez and Fautrez-Firlefyn, 1953). Thus, in spore germination the continuous rise of desoxvribonucleic acid, which ocCuIrs simultaneously with the sepaiation of the chiomatin, makes one seriously question the suggestion of Hunter and DeLamater (1952) that spore nuclei divide by a typical mitotic process. In the present paper, the arrangement of the chromatin in germinating spores of Bacillus cereuis and Bacillus megateriuni is examined, and