Automatic Adjustment in Bacterial Cells 323 



Application of the cytochemical methods of Holt and his 

 collaborators (Holt and O'Sullivan, 1958) has shown strikingly 

 that during mitosis enzymes normally having a peripheral 

 distribution in the rat liver cell gather into the nuclear region. 

 One very suggestive view of this phenomenon is that they are 

 called upon in some way to exchange information with the 

 nuclear elements themselves. 



Conclusive evidence about the protein/RNA/DNA inter- 

 dependence is still lacking. In the meantime, several lines of 

 investigation are yielding useful evidence. On the one hand, 

 cells may be broken down by various means, separated (e.g. 

 by centrifugation) into particulate ranges of different sizes, 

 and the residual biochemical properties of these can be 

 investigated. On the other hand, normal growth of intact 

 cells may be disturbed in various ways, by temperature 

 changes, by the addition of drugs, or the withholding of 

 growth requisites, and the consequent changes in function, 

 and in nucleic acid or protein content observed. Among 

 examples of such investigations may be cited work on the 

 inhibition of protein synthesis by chloramphenicol (Gale, 

 1958); Cohen's work on the unbalanced growth caused by 

 incubating a thymine-requiring mutant in a medium lacking 

 thymine whereby DNA synthesis is held up while certain 

 other growth processes continue (Earner and Cohen, 1954; 

 Cohen, 1957); and work on synchronization, whereby it 

 appears that the cells can be brought into a state where they 

 are ready in most respects for division except for the forma- 

 tion of sufficient DNA, so that when the synthesis of this 

 can go forward, all divide together. Some of the details of 

 this work are of special interest in connexion with the general 

 problem of regulation. 



The action of chloramphenicol on protein synthesis and on 

 nucleic acids has recently been fully reviewed by Gale (1958) 

 and need not be repeated here in detail. Of particular interest 

 to the present discussion is the work of Pardee, Paigen and 

 Prestidge (1957), Neidhardt and Gros (1957), Hahn and co- 

 workers (1957), Ben-Ishai (1957) and Earner and Cohen (1957). 



