JAMES WALTER McLEOD 213 



evidence to show that products capable of producing reduction diffuse out from bac- 

 teria, and the most convincing proof that the bacterial body is not essential has come 

 with the recent demonstration by Avery and Neill' that filtered extracts of pneumo- 

 cocci which are protected from oxidation have definite reducing properties. 



Although it is true that all bacteria are alike in reducing methylene blue and the 

 same can be said of oxyhemoglobin (Von Liebermann^), there exist considerable differ- 

 ences in their activities in this respect and greater differences in respect of other re- 

 ductions, e.g., in the reduction of anthraquinone. Bieling^ has shown that meningococ- 

 cus, pneumococcus, and B. typhosus are relatively inactive. 



The writer and Gordon'' have shown that when bacteria are grouped according 

 to their power of reducing glutathione they fall into the following order of activity: 

 streptococci and B. dyscnteriae Shiga, very poor reducers; Staphylococcus aureus 

 and pneumococcus, slight reducers, most bacteria of the coliform group, fairly ac- 

 tive reducers; anaerobic bacteria, all active and mostly very active reducers. Another 

 indicator of reduction less easily reduced than methylene blue — and hence more use- 

 ful in demonstrating differences in reducing activities — is hematin as it occurs in the 

 heated blood agar or "chocolate" medium. Colonies of anaerobic bacteria are sur- 

 rounded on this medium by a pink halo, due to reduction, which fades very rapidly on 

 exposure to air. This effect is shown in Plate I, A and B. It can be put to practical 

 use in picking out anaerobic colonies in mixed cultures on plates incubated under an- 

 aerobic conditions. 



A very interesting application of the bacterial reduction of methylene blue has 

 been made by Quastel^ and his collaborators by applying Thunberg's method in 

 studying the intimate processes of bacterial metabolism. The bacteria are suspended in 

 a buffered solution containing methylene blue, and the acceleration of the reduction 

 of the dye in the presence of various products which may occur in culture media or 

 arise in the course of the bacterial disintegration of sugars and proteins is investigated. 

 The marked powers shown by B. coli for activating the reduction of methylene blue 

 by certain sugars and fatty acids, notably formic, lactic, and succinic, and its relative- 

 ly slight powers of activating amino acids are among the interesting results obtained. 

 One other aspect of the work on the reducing action of bacteria has great interest, and 

 that is the suggestion made by Von Liebermann- but followed out with much greater 

 precision by Dibbelt,^ that the successful competition of bacteria with the body tissues 

 for the available oxygen of oxyhemoglobin may, especially in the more rapid septi- 

 cemias, be an important element in the domination of the animal body by the invad- 

 ing bacteria. 



' Avery, O. T., and Neill, J. M.: /. Exper. Med., 39, 357. 1924. 



^ Von Liebermann, Jr., L.: loc. cit. 



3 Bieling, R.: Cenlralbl.f. Bakteriol., Abt. I, Orig., 90, 48. 1923; Ztschr.f. Hyg. u. Infekiions- 

 krankh., 100, 270. 1923. 



■•McLeod, J. W., and Gordon, J.: Biochem. J., 18, 937. 1924. 



5QuastelJ.H.,andWhetham,M.D.: ibid., ig, ^ig. 1924; /&/(/., pp. 520 and 645. 1925; Quastel, 

 J.H.: ibid., p. 641. 1925; Quastel, J. H., Stephenson, M., and Whetham, M. D.: /6/(f ., p. 304. 1925; 

 Quastel, J. H., and Stephenson, M.: ibid., p. 660. 1925; Quastel, J. H., and Woolridge, W. B.: 

 ibid., p. 652. 1925. 



^Dibbelt, W.: Cenlralbl.f. Bakteriol., Abt. I, Orig., 64, 52. 1912. 



