On the nature of mitochondria. V. A critical analysis of Portier's Les symbiotesкод для вставкиСкачать
Resumen por el autor, I. E. Wallin. Sobre la naturaleza de las mitocondrias V. Un andisis critic0 de la obra de Portier “Les symbiotes” Portier en 1918 ha llegado a una concepci6n bacterial de las mitocondrias. Dicho autor cree que 10s “ symbiotes ” (niitocondrias) entran y salen del organism0 constantemente. Los “ symbiotes ” son organismos omnipresentes que exhiben extrema resistencia a 10s agentes fisicos y quimicos. Translation by Jos6 F. Nonidez Cornell Medical College, New York. AUTHOR’S ABSTRACT OF THIS P A P E R ISSUED B Y T E E B I B L I O G R A P H I C S E R V I C E , J A N U A R Y 29 ON THE NATURE O F MITOCHONDRIA V. A CRITICAL ANALYSIS OF PORTIER’S ‘LES SYMBIOTES’ IVAN E. WALLIN TRANSLATION B Y LOUISLABARRERE Department of Anatomy and the Henry S. Denison Research Laboratorips University of Colorado School of MedicinP, Boulder, Colorado. Since the publication of ‘‘ Die Elementarorganismen und ihre Beziehungen zu den Zellen” in 1890 there have been only a few expressions of opinion which have leaned towards Altmann ’s conception of mitochondria. These expressions have been more of the nature of opinions based on generalities than convictions arrived at from experimental and observational evidence. The major part of mitochondria1 literature, particularly that of recent years, has attempted t o establish a cytoplasmic origin for mitochondria. The success of this adventure may be measured by the uncertainty and indifference with which this conception has been received by biologists in general. It appears that the basis for a conception of cytoplasmic origin of these structures rests chiefly on topographical relationship. In its final analysis such a basis carries no more proof of origin than may be found in the old adage: “possession is nine points of the law.” Portier’s ‘Les Symbiotes’ (’18) is, apparently the first pretentious experimental work which supports, in part, Altmann ’s conception of mitochondria. While Portier ’s opinion differs from Altmann’s conceptions in many particulars, the two opinions agree in the essential part of the hypothesis, namely, that mitochondria are organisms of a bacterial nature. Independent of Portier ’s researches and on the basis of experimental grounds and evidence by analogy, the writer (Wallin 1922 a, b) has also arrived at a bacterial conception of mitochondria. The writer’s conceptions were arrived at from different lines of investigation than those employed by Portier. His conceptions are also 1 2 IVAN E. WALLIN quite different from Portier’s, especially in regard to the origin of mitochondria. Portier’s hypothesis may be better stated by quoting from the preface of ‘Les Symbiotes’: ‘‘Chaque cellule vivante renferme duns son protoplusme des formations que les histologists designenl sous le nom de mitochondries. Ces organites ne seraient pour moi autre chose que des bacteries symbiotiques, ce que j e nomme des ‘symbiotes’ . . . L a bacterie symbiotique vient d u milieu exterieur: elle peut, duns certains cas, y retourner et vivre d ’une vie independante. Les bacteries seraient donc les seuls etres simples; tous les autres seraient doubles. ’’ The chief basis for Portier’s conclusions rests on his results from attempts to grow mitochondria in artificial culture media. The results innthese attempts have not been successful with all tissues. The successful growths were obtained chiefly from the fat in relation to the sex organs, particularly the testes. Attempts at cultivating the mitochondria of the pancreas and liver, for example, have been unsuccessful. This failure is accounted for on the basis of his general theory regarding the nature and relationship of mitochondria. Portier believes that the ‘symbiotes ’ are especial microorganisms found in great abundance in nature. They are constantly entering and leaving the host organism under normal conditions. After entering a host they first occupy an intercellular position and later take up an intracellular relationship. In the intercellular relationship the organisms retain their hardy properties and are easily cultivated in culture media. After the ‘symbiotes’ have taken up the intracellular position they lose their hardy qualities, develop fragility and are quite incapable of cultivation in culture media. A remarkable characteristic of Portier ’s ‘symbiotes’ is their extraordinary resistance to chemical and physical agents. The organisms after a number of passages in culture may be brought to a moist temperature of 115” C. before they are destroyed. I n a state of desiccation they resist temperatures up to 150’ C. ‘Symbiotes ’ in culture media resist the action of absolute alcohol and chloroform for a period of a year. Further, the organisms resist 5 per cent phenol for more than fifty hours, 20 per cent ON THE NATURE O F MITOCHONDRIA 3 formaldehyde for twenty five hours, and 10 per cent tincture of iodine for twenty four bours. The organisms may be exposed to the action of X-rays for considerable periods of time without being destroyed. The temperature at which the ‘syinbiotes’ were cultivated varied with the source of the ‘symbiotes.’ The organisms from higher vertebrates were best grown at a temperature of 40” C. while those from invertebrates were cultivated at a temperature of 25” C. In all the cultural experiments only one type of organism was produced for each temperature group. The culture media used were ordinary bacteriological media. The experiments were apparently conducted with particular precautions to guard against contaminations. The room in which the work was done was thoroughly scrubbed, the instruments used were sterilized in a flame and other general precautions were observed. The cultural experiments were repeated a number of times with constant results. There is a great temptation to drift into fields of pure speculation when one is dealing with a problem of the nature of mitochondria. In a bacterial conception of these structures one faces a myriad of possibilities in life processes and biological relationships that suggest an entirely new and unique conception of life. Altmann could not resist this temptation and his speculations led him into conflict with established facts in biology. Portier discusses various functional relationships of ‘ symbiotes’ to the cell, both normal and pathological. While these speculations are interesting their significance is dependent upon the determination of the nature of mitochondria. The premises for Portier’s researches rest on a statement attributed to Louis Pasteur in which he maint,ained that the tissues of a healthy animal are free from bacteria. This statement leads Portier to differentiate between the ‘interior medium’ which is aseptic and the ‘exterior medium’ which contains numerous microorganisms. It is difficult to determine just what Portier means by ‘interior’ and ‘exterior’ media. From the content of his dissertation it appears that the ‘interior’ medium is an intercellular medium and the ‘exterior’ medium 4 IVAN E. WALLIN refers to any position that is physiologically outside of the body. Pasteur ’s statement concerning the aseptic condition of the tissues of healthy animals is undoubtedly erroneous. Medical literature in recent years contains a number of observations which refute this statement. Gurney-Dixon (’20) claims to have found bacteria present in 80 per cent of apparently healthy animals. The writer’s experience in this direction does not agree with Pasteur’s contention. I n a few attempts I have been able to get luxuriant bacterial growth on the ordinary agar culture media from lymph nodes of apparently healthy young rabbits and kittens. While an attempt has not yet been made to determine the relative prevalence of bacteria in the tissues of apparently healthy animals, these preliminary experiments point to a relatively high percentage of prevalence. If bacteria are normally present in the tissues of apparently healthy animals, it is obvious that the fundamental basis for Portier ’s experiments is faulty. Portier made his cultures from the tissues of adult animals. It is quite impossible to determine whether he was dealing with intercellular symbiotic organisms which are, apparently, normally present or if he actually produced cultures from mitochondria. It is difficult to harmonize Portier’s ‘symbiotes’ with the known microorganisms. Their remarkable resistance to physical and chemical agents would suggest a hitherto unknown type of organism. Obviously, with such characteristics they are not identical with mitochondria. That they are the extracellular representatives of mitochondria remains to be demonstrated. Such free living and hardy forms fit well into Portier ’s hypothesis. However, there are certain conditions which Portier has not taken into consideration, conditions which have a decided bearing on the solution of the origin of mitochondria. Portier believes that the ‘symbiotes’ are constantly entering the host organism by way of the alimentary tract. This assumption is based on various observations on the presence of bacteria in the intestinal lumen and cells of insects and rabbits. In the rabbit he found bacteria in the intestinal contents, and apparently the same strain of bacteria within the epithelial cells of the intestine. The ON THE NATURE O F MITOCHONDRIA 5 writer has made the same observation on a one-day old kitten. Portier further observed that some of the bacteria in the insect intestinal epithelium were digested within the iell: Some of the apparently ingested bacteria, however, he maintains are retained intact within the cell. There is very little room for doubt concerning the ingestion of some bacteria by the intestinal epithelial cells. However, there appears to be no relationship between this phenomenon and the origin of mitochondria. While it is possible that the intestinal tract may be the avenue of entry for ‘new symbiotic complexes,’ the perpetuation of such a new symbiotic complex is by way of the germ cell. The presence of mitochondria in the germ cell has been demonstrated beyond a doubt. Their increase by simple division in embryonic differentiation has also been observed. The possibility of a functional and morphological differentiation in the developing host is supported by the analogous conditions which are present in the differentiation of the symbionts in the higher lichens. Aside from his results in the cultural experiments in ‘symbiotes,’ Portier has brought forth a number of observations which support a bacterial conception of mitochondria. A great portion of this evidence deals with the relationship of bacteria to insect life. These bacterial forms are not mitochondria. If they are ‘symbiotes ’ they strengthen Portier ’s hypothesis, but this remains to be determined. However, in many instances they do furnish examples of bacterial relationships to higher organisms which are similar to the relationships of mitochondria to the cell. It is quite certain that a definite transplantation of rnitochondria to an artificial culture medium would constitute conclusive evidence of the organismal character of mitochondria. The failure to accomplish such growth, however, is not evidence of a cytoplasmic origin of mitochondria. 6 IVAN E. WALLIN LITERATURE CITED ALTMANN,R. 1890 Die Elementarorganismen und ihre Beziehungen zu den Zellen. Leipzig. GURNEY-DIXON1920 The transmutation of bacteria. Cambridge. PORTIER, P. 1918 Les Symbiotes. Masson, Paris. WALLIN,IVANE. 1922 a, On the nature of mitochondria. 1. Observations on mitochondria staining methods applied to bacteria. 2. Reactions of bacteria to chemical treatment. Am. Jour. Anat., vol. 30, no. 2. 1922 b, On the nature of mitochondria. 3. The demonstration of mitochondria by bacteriological methods. 4. A comparative study of the morphogenesis of root-nodule bacteria and chloroplasts. ilmer. Jour. Anat., vol. 30, no. 4.