346 VIII. HEMATIN ENZYMES, I. CYTOCHROME SYSTEM 



It is evident from this that the spectroscopic distinction between 

 b and bi, and to a smaller extent that between bi and c, is not always 

 possible. Moreover, in a mixture of two compounds the absorption 

 maxima of which are not far apart, the two bands can appear as one 

 of intermediate position. Thus Yamagutchi {311^6) claimed the 

 presence of cytochrome c in Escherichia coli, while Keilin and Harpley 

 (1484), using spectroscopy at the temperature of liquid air, established 

 its absence. 



Table I contains a classification of various microorganisms based 

 on their cytochrome spectrum, which is mainly derived from the 

 paper of Fujita and Kodama {962). 



TABLE I 

 Cytochrome Spectra of Microorganisms 



Cytochrome Microorganisms 



a, b, c 



c prevailing Saccharomyces cerevisiae (bakers' and aerobic brewers' yeast). 



Neisseria gonorrhoeae, N. irUracellularis, Hemophilus pertussis. 



Bacillus subtilis, Serratia marcescens 



b = c Pseudomonas fluorescens, Ps. aeruginosa (pyocyanea) 



b>e Corynebacterium diphtheriae, Mycobacterium tuberculosis. Hemo- 

 philus influenzae. Bacillus anthracis, Sarcina 



a, bi Staphylococcus 



Bi, b, c 5'. cerevisiae (anaerobic brewers' yeast), Vibrio cholerae, Alcali- 



genes faecalis 



aa. ai> b, c Acetobacter pasteurianum, A. aceti, Azotobacter 



ao. El, bi Many facultative anaerobes and most pathogenic intestinal 



bacteria. Escherichia coli, E. metacoli. Shigella dysenteriae, S. 



paradysenteriae, Eberthella typhosa. Salmonella paratyphi, S. 



abortivoequina, Proteus vulgaris 



Keilin (lJf.80,14.81) drew attention to the fact that the bacteria 

 contain either cytochrome a or ai and a2. Later he showed, however, 

 that "cytochrome a" is a mixture of two compounds, cytochromes a 

 and aa, the latter resembling cytochrome ai more closely in its 

 behavior than cytochrome a. Since these observations are of impor- 

 tance for the theory of the respiratory enzyme they will be discussed 

 in this connection below. Cytochrome ai predominates in Acetobacter 

 (Bacterium) pasteurianum, in which it was discovered by Warburg and 

 Negelein (2955). It also occurs in brewers' yeast (660, 7 60, 3307, 295 J^) 

 and a somewhat similar band has been observed in bakers' yeast 

 treated with caprylic alcohol (11^80). Cytochrome aj was discovered 



