154 MICROSOMAL PARTICLES 



on being forced through the orifice of the pressure cell. Cell juices prepared 

 with the pressure cell do not show the peak characteristic of DNA in their 

 sedimentation diagram [4]. It is these preparations (made with the pressure 

 cell) that will not give protomorphs when diluted. In contrast, preparations 

 made by grinding the cells with alumina or by lysozyme treatment followed 

 by osmotic shock (methods which preserve DNA) do yield protomorphs even 

 at one-tenth the usual concentration. Finally, the addition of DNA to dilute 

 pressure-cell preparations restores the yield. It seems quite likely that varia- 

 tions in the pressure and in the conditions at the orifice during the disruption 

 of the cells affect the quantity of intact DNA remaining and thereby influence 

 the yield in an erratic way. 



The formation of protomorphs was photographed by Drs. B. Hoyer and 

 N. Kramis, of the Rocky Mountain Laboratory, U. S. Public Health Service. 

 Their time-lapse photomicrography shows that the growth of an individual 

 protomorph from its first appearance to full size requires only a few minutes 

 after a much longer induction period. There may well be a slow process of 

 nucleation followed by a rapid process of growth. Neither fission nor fusion 

 played any part in the growth process. 



Once formed, the protomorphs are stable. Unlike simple coacervate particles 

 which exist only in a narrow pYL range and have a strong tendency to fuse 

 or to dissolve, protomorphs can be handled like bacteria or yeast. There is no 

 difficulty in centrifuging the photomorphs into a pellet (lOOOg-) and resuspend- 

 ing in fresh media. They are quite stable in a number of ordinary media, and 

 persist for weeks even though overgrown by bacterial contamination. They 

 are not dissolved by short exposures to ammonia (1 M), 5 per cent trichloro- 

 acetic acid (TCA), ethanol, or ether. They are dissolved in 0.01 M ethylenedi- 

 aminetetraacetic acid to give a clear solution. 



On standing, glass vessels containing protomorph suspensions develop a 

 white film over the surface. Microscopic examination of the material scraped 

 from the glass indicates that the protomorphs have formed a moderately well 

 packed monolayer on the surface (fig. 2). 



The organic components of the particles had roughly the proportions found 

 in living tissues. They contain ultraviolet-absorbing material which hydrolyzes 

 to yield the bases expected from ribonucleic acid. In addition the diphenyl- 

 amine test [5] indicates that a small part (10 per cent) of the ultraviolet absorp- 

 tion is due to DNA. The ratio of nucleic acid to protein (measured by the 

 Folin reaction [6]) is 1/6 as compared to 1/4 in the bacterial juice. Paper 

 chromatography shows the presence of lipid material. 



Incorporation experiments were carried out with thoroughly washed prepa- 

 rations of protomorphs. Radioactive phosphate was incorporated at a constant, 

 high rate for several hours. This process was not studied in any detail because 

 all the radioactivity so incorporated could be extracted with cold TCA and 

 there was no evidence of incorporation into macromolecules. 



The incorporation of radioactive amino acids was of more interest. The re- 



