SUMMARY: The chromatin configurations of acid-Giemsa preparations of were followed sequentially, at 2 hr. intervals, for 48 hr. A series of broth cultures were inoculated with 0·1 ml. of a 7-day broth culture, incubated at 30° and centrifuged at 2 hr. intervals. The sedimented cells were used to inoculate agar plates for use in making smears by the agar block method. The smears were fixed in acid-alcohol, hydrolysed in N-HCl solution at 60° for 8 or 15 min. and stained with Giemsa. Samples of living cells, taken from the sedimented cells at all time intervals, were examined by phase-contrast and darkfield microscopy.

The majority of the early cells (0–16 hr.) were resistant to acid hydrolysis, being undifferentiated by 15 min. of hydrolysis until the 12th hr. of growth. After the 16th hr. of the growth cycle the cells showed an abrupt change in their reaction toward acid hydrolysis; subsequent preparations were hydrolysed for 8 min. The early cells appeared undifferentiated by phase contrast until approximately the 14th hr. of growth; after this time inclusions could be observed in the cells. Transparent cells containing dark inclusions were observed in the living cells by the 16 hr. of growth and coincided with the abrupt change of the acid-Giemsa cells toward acid hydrolysis.

The pattern of the chromatin configurations found in the acid-Giemsa cells consisted in: (1) an axial filament which fragmented into thick bars, from which spherical bodies were formed; (2) the direct division of the spherical bodies into smaller spheres, from which bead-like granules were formed by means of intermediate X-, Y-, and V-forms or the direct formation of rings of bead-like granules from the spherical bodies; (3) the re-formation of the axial filaments from the bead-like granules with the aggregation of all the chromatin material of the cell at the centre of the cells; (4) the division of the aggregated chromatin material on cell division and the extension of the chromatin material in the form of an axial filament; and (5) the re-formation of the spherical bodies and bead-like granules as outlined in steps (1) and (2) from the axial filaments.

Essentially the same types of chromatin configurations were observed in living cells. The most exact correlation between the living and fixed images of the chromatin bodies of occurred between the 18th and 30th hr. of the growth cycle. The correlation between the living and fixed images of the chromatin bodies of was less exact at other time intervals. Various theories concerned with the occurrence of axial filaments and chromatin aggregations in bacterial cells are discussed.


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