The cytochemistry of bacterial nuclear structures. An examination of the feulgen nuclear, Piekarski-Robinow, and ribonuclease technics.

The highly specific feulgen reaction for demonstrating desoxypentose nucleic acid has proved to be of unequal utility in the hands of bacterial cytologists for the study of the bacterial nucleus (Milovidov, 1935), and at present the principal cytochemical evidence is derived from basic staining following hydrochloric acid hydrolysis or following ribonuclease digestion. It has been generally accepted (Boivin, 1948; Knaysi, 1951) that these technics will remove all pentose nucleic acid from bacteria, and thus any remaining basophilic structures which occur regularly and appear to give division figures are nuclear organelles containing only desoxypentose nucleic acid. However, the available chemical evidence does not fully support the view that all pentose nucleic acid is removed from the cell by acid hydrolysis or ribonuclease digestion. Vendrely and Lipardy (1946) reported that hydrolysis for 10 minutes in N/1 hydrochloric acid at 60 C removed most but not all of the pentose nucleic acid from a micrococcus and coliform bacillus, but they failed to give the percentages. Pouyet (1949) found that 10 per cent of the pentose nucleic acid in calf thymus remained after acid hydrolysis for 10 minutes, and 31.3 per cent of the pentose nucleic acid remained in calf pancreas under the same conditions. He attempted to explain the failure to remove all the pentose nucleic acid by assuming that the acid did not thoroughly penetrate the finely chopped tissue. The findings with ribonuclease are similar. Bacher and Allen (1950), for example, found that one-quarter of a yeast pentose nucleic acid preparation was nondialyzable following digestion with Kunitz-type ribonuclease. Loring et al. (1947) reported that about 50 per cent of yeast pentose nucleic acid subjected to ribonuclease digestion remains as a relatively nondialyzable fraction which cannot be further hydrolyzed by the enzyme. As Bacher and Allen pointed out, the specificity of ribonuclease is probably such that not only certain specific linkages but also a certain arrangement of groups adjacent to the linkages in the substrate are necessary for action. It is not surprising, therefore, that a second