BIOCHEMISTRY OF MICRO-ORGANISMS 



107 



the fundamental significance of this gas as 

 the agent needed for the slow combustion 

 of organic matter — which is respiration — 

 could van Leeuwenhoek 's contribution be 

 fully appreciated. But by that time it had 

 been forgotten, so that Lavoisier felt it safe 

 to conclude that oxygen was needed for life. 

 Still, van Leeuwenhoek 's discovery implied 

 a basic principle; and confirmation of the 

 occurrence of organisms living in the 

 absence of air was but a matter of time. 

 To the genius of Pasteur we owe the con- 

 cept of fermentation as the equivalent of 

 respiration, and "the consequence of life 

 without air," a concept which was based 

 entirely upon Pasteur's studies (1876) of 

 the activities of micro-organisms.^ 



The fundamental similarity of respira- 

 tion and its anaerobic counterpart of fer- 

 mentation soon became more generally 

 accepted. It will remain one of the great 

 merits of Max Rubner (1909) to have em- 

 phasized these two aspects of metabolism as 

 expressions of one and the same principle: 

 the means of providing the living organism 

 with energy. I need but refer to his pains- 

 taking and exhaustive studies on alcoholic 

 fermentation (1913) in which he estab- 

 lished so conclusively that in the absence 

 of air this process is the only detectable one 

 which can supply the organism with 

 energy. Thus Rubner brought to a close 

 that period, following Buchner and Hahn's 

 discovery of cell-free fermentation, during 

 which a number of scientists had begun to 

 look upon alcoholic fermentation as a pro- 

 cess completely divorced from the vital 

 activities and functions of a living organ- 

 ism. 



In connection with the importance of the 

 chemical activities of organisms as a source 

 of energy, mention should also be made of 

 the brilliant hypothesis, advanced by Wino- 



3 ' ' En resume, la fermentation est un phenomene 

 tres general. C 'est la vie sans air, c 'est la vie sans 

 gaz oxygene libre, on, plus generalement encore, 

 e 'est la consequence d 'un travail cliimique accompli 

 au moyen d 'une substance f ermentescible capable 

 de produire de la chaleur par la decomposition, 

 travail qui emprunte precisement la chaleur qu'il 

 consomme a une partie de la chaleur que la decom- 

 position de cette substance fermenteseible met en 

 Uberte." 



gradsky (1887), that living organisms 

 might be able to utilize the energy released 

 in the oxidation of inorganic substances 

 (1888, 1891). If so, such organisms would 

 be able to get along with very much smaller 

 amounts of organic matter, most of which 

 is ordinarily respired away; the inorganic 

 substrate would here fulfill the same pur- 

 pose and function'* (Winogradsky 1887). 



Nay, it would even be possible that living 

 organisms might exist which could use part 

 of the energy obtained from the oxidation 

 of inorganic substances for the conversion 

 of carbon dioxide into cell materials, a 

 process known until that time to happen 

 only in the green plants during illumina- 

 tion. This remarkably bold conception of 

 the existence of what has later been termed 

 the chemosynthetic mode of life was first 

 experimentally verified by Winogradsky 's 

 studies (1890, 1891, 1904) on nitrifying 

 bacteria, later by many other workers and 

 for a number of different groups of bac- 

 teria.5 (Cf., e.g., Knight 1936; Stephen- 

 son 1939). 



It thus appears that the various types of 

 energy providing metabolic processes which 

 exist in addition to ordinary respiration 

 became known, one and all, through studies 



4 ' ' Betrachten wir einen dem gewohnlichen physi- 

 ologischen Typus angehorigen Organismus, so sehen 

 wir, dass von den complicirten organischen Ver- 

 bindungen, Kohlehydraten z. B., welche er ver- 

 braucht, nur ein Theil zum Aufbau seines Korpers 

 dient; der andere wird verathmet, zerstort, wobei 

 actuelle Energie disponibel wird. Und zwar ist der 

 letztere Theil constant grosser als der erstere, 

 manchmal unvergleichlieh grosser. Der grosste 

 Theil der organischen Stoffe wird also zum 6e- 

 winnen der fiir den Organismus nothigen Arbeits- 

 kraft verbraucht. Gerade der Verbrauch dieses 

 grossten Theiles fiillt bei den Schwefelbacterien 

 ganz weg. Die Energie beziehen sie ausschliesslich 

 aus dem Schwef eloxydations-Processe. " 



5 ' ' Die ganze Zeit hindurch ging die Ent\vick- 

 lung wie auch die Oxydation sowohl im Lichte als 

 auch in vollstandiger Dunkelheit in bester Weise 

 vor sich, was wohl zu dem Schlusse berechtigte, 

 dass der Nitritbildner normal wachsen und kraftige 

 Wirkung in einem Nahrboden ausiiben kann, 

 welcher keine Spur von organischer Substanz ent- 

 halt. Daraus folgte aber mit Notwendigkeit der 

 Schluss, dass dieser Organismus die Fahigkeit 

 haben muss, Kohlensaure zu assimilieren und zwar 

 durch einen vom Lichte unabhangigen Prozess. " 

 (Winogradsky 1904, p. 163.) 



