CHAPTER XIII 

 ANAEROBIOSIS 



IVAN C. HALL 



University of Colorado Medical School 



BIOLOGICAL SIGNIFICANCE OF ANAEROBIOSIS 



Few biological discoveries of more fundamental significance have been made than 

 when Pasteur' in 1861 proved the existence of micro-organisms that are able not only 

 to live in the complete, or nearly complete, absence of atmospheric oxygen, but which 

 are actually unable to multiply at all under ordinary atmospheric conditions, and re- 

 quire, if not an absolute elimination of free oxygen from their environment, at least a 

 marked reduction in oxygen tension. 



Pasteur was brought to this discovery during his famous researches on fermentation, 

 by the observation that certain motile germs in a cover-slip preparation became non-motile 

 on approaching the edge of the cover. Having noted that many products were formed in 

 the so-called "lactic" fermentation, such as butyric acid, mannitol, alcohol, carbon dioxide, 

 and hydrogen, in addition to lactic acid, he was led to investigate the possibility of a special 

 butyric ferment. This he decided was an infusorian, the Vibrion butyrique, living only in 

 the absence of free oxygen, a conclusion in error so far as concerns the animal nature of the 

 organism, but none the less important in its implications and its bearing on the old problem 

 of abiogenesis. It had been generally assumed that air was necessary for the existence of all 

 living things. But Pasteur revealed that the growth of certain micro-organisms is not only 

 not inhibited but is actually dependent upon the practically complete exclusion of air. 



Pasteur^ called these organisms "anaerobes," as distinguished from "aerobes," which 

 grow in the presence of air; later^ three groups were distinguished: obligate anaerobes, obli- 

 gate aerobes, and facultative aerobe-anaerobes. Holding that all anaerobic life depends upon 

 an ability to satisfy oxygen requirements by sugar cleavage, Pasteur was led to define 

 fermentation as life without air. While the production of "ferments" or enzymes is by no 

 means restricted to the anaerobic micro-organisms, as Pasteur believed, both the most 

 actively fermentative and the most actively putrefactive bacteria are found within this 

 group. They are therefore of great importance in the chemical cycles of nature for the 

 mineralization of organic matter, including processes useful to man, such as the destruction 

 of dead bodies of plants and animals, and the formation of useful chemical solvents (butyl 

 alcohol and acetone), as well as processes which man would like to avoid, notably food 

 spoilage. Some of the obligate anaerobes are dangerous pathogens, producing malignant 

 edema, gaseous gangrene, tetanus, botulism, syphilis, and other diseases in man and animals. 

 The toxins of tetanus and botulism are the most powerful bacterial poisons known. 



The first pathogenic anaerobe, Vibrion septique, was announced by Pasteur and Joubert 

 in 1877 as the cause of a septicemia {charbon symplomaliquc, symptomatic anthrax, or 



' Pasteur, L.: Compl. rend. Acad, de sc, 52, 344 and 1260. 1861. 

 ^ Pasteur, L.: ibid., 56, 416 and 1192. 1863. 

 i Pasteur, L.: Eludes siir la Bicre. 1876. 



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