TEMPERATURE SYNCHRONIZATION OF NUCLEAR AND CELLULAR DIVISION IN BACILLUS MEGATERIUM,

It was accidentally observed by the senior author that, when agar plates supporting young cultures of Bacillus megaterium were stored for a short time in the refrigerator, the cytological picture was strikingly and uniformly changed. The nuclear material of actively growing cells appears both filamentous and granular (figure 1). Stained nuclei of refrigerated cells (figures 2 and 3) became highly condensed masses with two distinct granules, in a configuration suggesting the mitotic figure. Similar action of chemical bacteriostatic agents on divisional stages of the microbial nucleus was recently described by the present authors (DeLamater, 1953; DeLamater et al., 1955). On the other hand, it is well known that low temperatures may affect the course of mitosis or meiosis in cells of many organisms (Belling, 1925; Barber and Callan, 1943, among others). Chilling decreases the rate of chemical 1 A summary, of this work was presented at the 55th meeting of the Society of American Bacteriologists, New York City, May 8-12, 1955 (Szybalski and Hunter-Szybalska, 1955). 2 The preliminary observation and the cytological studies of the effect of cold on agar-grown bacteria (including figures 1-3) were performed at the University of Pennsylvania, under the support of grants from the Atomic Energy Commission, Conitract No. AT-(30-1)-1341, from Eli Lilly and Company, and from the National Institutes of Health, l'ublic Health Service (PHS No. C-2189). Subsequent studies herein reported on synchronized growth in broth with simultaneous nuclear staining and microphotography were executed at Rutgers University by W. S. with the collaboration of the first author. 3Present address: Warner-Chileott Laboratories, Morris Plains, N. J. 4Present address: Section on Cytology and Genetics, Department of Physiology, School of Mledicine, University of Pennsylvania, Philadelphia 4, Pa.