Gary Steinman Pennsylvania State University University Pork A ~ O I PE.~Smith Sir G e o r g e Williams University Montreal, Canada
II
A "Primordial Biogenesis" Experiment
A number of models have been proposed and investigated to demonstrate how cell precursors may have developed on the primitive Earth1. One of the most intriguing, originally advanced in the early part of this century2 and recently e ~ t e n d e demploys ,~ formaldehyde and ammonium thiocyanate. This mixture, when incubated for a time or irradiated by ultraviolet light, yields dynamic microscopic bodies. These microspheres display the formation of internal structures resembling vacuoles which grow with time. The spheres, which look very much like coccoid bacteria, combine with each other to increase in size. They interact with the environment to concentrate particular compounds and act to localize biologically pertinent reactions. That the reactants themselves could have been found on the primitive Earth has already been demonstrated.' Thus, the phenomena noted here, by their resemblance to living processes, suggest that the thiocyanateformaldehyde system could serve as one possible explanation for the primordial genesis of protocells. The supermolecular morphogenicity displayed by the simple reactants used in this model supports the contention that primordial biogenesis can be understood in terms of recognizable physical and chemical properties.' While no suggestion is made that these microspheres are in
fact "alive" or that they are the one and only explanation for protocell developn~ent,the process itself brings out some very interesting new insights. The simplicity of the procedure makes it readily amenable for incorporation in an introductory biological sciences laboratory course or a lecture demonstration. The equipment and proficiency needed are minimal, the manipulation required is very short in duration, the cost is very low, and the results are truly exciting and stimulating. The experiment can be carried out as follows: To 7 ml of 37% formaldehyde is added 3 g of ammonium thiocyanate. (The volumes and concentrations are not critical.) After 1 hr a t room temperatwe the clear solution turns golden yellow. Ult,raviolet irradiat,ion (Hg-quarts) catalyzes the reaetion but is not essential for the reaction to t,ake place under the conditions just noted. A drop of the prodrlet is placed on a microscope slide. Next to the prodoct solution a drop of water is applied so that the two slightly overlap each other (to simulate tidal action). Vigorous streaming results. Spheres in the range of 1-100 r in diamet,er can be ohserved with a standard laboratory (see fignre). microscope w i t h o ~ shining ~t
Much movement can be detected between spheres and within them. With careful observation it is possible to see the formation of internal vacuole-like structures which grow and are then exuded outward. This experiment can be extended to include reaction localization and staining, as previously descrihed.3 In any case, experience in our laboratories has shown that the investment. of a small amount of time and supplies yields an experiment which attracts the active interest of many a young budding scientist,. This work was supported by t,he National Aeronautics and Space Administration (USA) and the National Research Council (Canada). ' KENYON, D. H., A N D STEINMAN, G., "Riochemieal Predesha'
Spheres formed a t the interface between water and a drop of the product synthesized from formaldehyde and ammonium thiocyanote. The larger microspheres are fabricated b y amdgomation of mony smaller bodies upon rehydration of the product mixture.
tion", McGraw-Hill Book Co., New York, in press. HERRERA, A. L., Brrh. Plasmol. Gdndmle, 1 , 55 (1912); Bull. Labor. Plasmogdnie, 2 , 1 (194042); Science, 96, 14 (1942). a SMITH, A. El, SILVER, J. J., A N D STEINMIN, G., Ezperienlia, 24, 36 (1068); Science, 159, 1108 (1968); Biophysical Sociell~ Meeting, Pittsburgh, Fehrnsry, 1968. MILLER,S. L., J. Am. Chem. Soe., 77, 2351 (1955); Hau~s, K., WALTER, W., A N D MAYER, E., hiatumi~s.,44, 31(1957).
Volume 45, Number 9, September 1968
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