2o8 ANAEROBIOSIS 



growth through enzymic action cannot be denied; indeed, a most interesting theory 

 of anaerobiosis depends upon this conception. 



In 1922 M'Leod and Gordon' discovered that the early death of the pneumococcus 

 in cultures was apparently due to the accumulation of peroxide (of hydrogen?), for 

 the production of which evidence was found in the green discoloration of "chocolate" 

 blood agar, and in the liberation of oxygen from pneumococcus cultures by liver cata- 

 lase. Streptococci and other bacteria also produce peroxide, and it was suggested that 

 the well-known beneficial action of fresh tissues upon various bacteria is due to the 

 destruction of detrimental peroxide by catalase.^ 



NeilP holds that the oxidation and reduction reactions of sterile plant tissues are 

 essentially identical with those of pneumococci and anaerobic bacteria and furnish 

 the best explanation, thus far, for the beneficial action of raw plant and animal tissues 

 upon anaerobic growth. On the other hand, Novy^ holds that "the inability of an- 

 aerobes to grow in the air is not due to the hypothetical production of peroxide and to 

 the absence of catalase" but "that the fundamental difference between obligative 

 aerobes and anaerobes lies in the nature of the respiratory enzymes, which are des- 

 ignated as 'aerase' and 'anaerase,' respectively. The potato and the facultative an- 

 aerobes possess both types; that present in obligative anaerobes can function only in 

 the absence of oxygen, while that of the aerobe can work only in the presence of 

 oxygen." All living protoplasm respires, and Novy's conception of the beneficial ac- 

 tion of plant tissues upon anaerobic growth dispenses with the peroxide-catalase 

 hypothesis and emphasizes the idea that obligate anaerobes grow in the presence of 

 raw plant tissues because the latter reduce the oxygen tension, just as aerobic bacteria 

 do, below the toxic concentration. 



AEROBIZATION OF THE ANAEROBES 



Many of the investigations just discussed had for their aim the aerobic cultivation 

 of the anaerobes with the end in view of a better understanding of the nature of an- 

 aerobic growth. A secondary consideration has been in some cases that if means were 

 found to cultivate the anaerobes aerobically upon solid media, the technique of isola- 

 tion might be simplified. But no one has yet succeeded in securing surface growth of 

 any obligate anaerobe in pure culture upon solid media exposed to the air, and the 

 best practical definition of obligate anaerobes separates them from aerobes by their 

 failure to grow in pure culture on the surface of solid media at normal atmospheric 

 pressure. From this standpoint the rather numerous claims of aerobic growth in liq- 

 uid media through the addition of chemical reducing agents, symbiotic aerophilic 

 micro-organisms, fresh animal or plant tissues, or particulate substances have no 

 standing; all of these are really anaerobic cultivations. Even the symbiotic growth of 

 aerobes and anaerobes upon the surface of solid media fails to comply with the fore- 

 going definition of "anaerobiosis." The same is true of the supposed aerobic culture 



' M'Leod, J. W., and Gordon, J.: Biochem. J ., 16, 499. 1922; J . Palh. 6" Bad , 25, 139. 1922; 

 26, 127. 1923. 



^ See chap, xiv of this vohime. 



3 Neill, J. M.: /. Exper. Med., 41, 535. 1925. 



-•Novy, F. G., Jr.: loc. cil. 



