The structure, composition, and behavior of the nucleus in Bacillus cereus.

The author has recently reviewed the literature on the organization and behavior of the bacterial nucleus (Knaysi, 1951). Since then the situation has been confused by claims (DeLamater, Hunter, and Mudd, 1952) that the organization and behavior of the bacterial nucleus are identical to the organization and behavior of nuclei in the cells of higher animals. These claims have not been confirmed by others (Knaysi, 1952a, b, c, 1954; Robinow and Hannay, 1953; Bisset, 1954). Observation of the forespore nucleus of Bacillus cereus (Knaysi, 1952a) on living cells with the phase microscope and on stained preparations indicated the presence of two dumbbell-like bodies, hyaloplasm, and nuclear membrane. Similar observations on Mycobacterium thamnopheos (Knaysi, 1952b) showed that the nucleus in growing cultures usually contains one to several dumbbell-like bodies interpreted as chromosomes. Occasionally, however, a nucleus is found that contains ellipsoidal bodies. The most common picture is one in which the nucleus consists of two, curveed, dumbbell-like bodies separated by dense, homogeneous material interpreted as hyaloplasm. In actively growing cultures many nuclei consist of a single, dumbbell-like body often surrounded by a thin layer of the dense material that we called hyaloplasm. Other recent papers dealing with the structure of the nucleus are those of AMurray and Truant (1954) and Truant and Murray (1954) in which those authors report observin) vesicular nuclei with peripheral chromatin granules connected by 1 Reports on the progress of this investigation were made at the 52nd meeting of the Society of American Bacteriologists (Boston, 1952), to the Soci6te Frangaise de Microbiologie (Paris, May 5, 1953), and to the 6th International Congress of Microbiology (Rome, September 7, 1953). An abstract of the latter report appeared in the Riassunti delle Comunicazioni of the Congress and was later published in full with only two of the illustrations in Knavsi (1954). delicate threads, respectively, in Moraxella and in Azotobacter.