19 



The Formation of Protomorphs 



FRANK T. McCLURE 1 RICHARD B. ROBERTS 



Department of Terrestrial Magnetism 

 Carnegie Institution of Washington 



Disrupted cells of Escherichia coli were suspended in a number of different 

 solutions to find which ones were suitable for making stable preparations of 

 ribosomes. Among those tested were some containing manganese and mag- 

 nesium, because these ions had been found essential for incorporation of amino 

 acids by cell-free systems [1, 2]. After standing for several hours these solu- 

 tions became turbid and finally gave a white precipitate of unusual appearance. 



Examination of these solutions in the phase contrast microscope showed that 

 the turbidity was caused almost entirely by the presence of large numbers of 

 nearly spherical, highly refractile particles with diameters of 1 to 5 microns 

 (figs. 1 and 2). 



The appearance of these cell-like particles in a solution that originally con- 

 tained nothing visible in the microscope was quite surprising. The formation 

 of large, stable aggregates with distinct boundaries from a fluid containing 

 macromolecules in a homogeneous suspension seemed to illustrate a process 

 which perhaps was important in the origin of life. Accordingly, we proceeded 

 to investigate some of their properties. It was soon found that the particles con- 

 tained protein, nucleic acid, and lipid in proportions typical of biological ma- 

 terials. Because they are formed from protoplasm and have distinctive shape 

 we refer to them as "protomorphs" to distinguish them from other particles 

 or structures that exist in the living cell. 



The usual procedure for preparation of protomorphs is as follows: Harvest 

 10 g wet weight of Escherichia coli cells growing in synthetic medium "C" [3]. 

 Wash twice with tris(hydroxymethyl)aminomethane-succinate buffer, 0.01 M, 



1 Present address: Johns Hopkins University, Applied Physics Laboratory, 8121 Georgia 

 Avenue, Silver Spring, Maryland. 



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