55^ XI. HEMOGLOBIN CATABOLISM, I 



Bienstock destroyed bilirubin without forming urobilin, but that other strict 

 anaerobes such as Clostridium welchii effected the transformation. These 

 early experiments, particularly those of Passini, were unsatisfactory for 

 chemical as well as for bacteriological reasons. Instead of pure bilirubin, bile 

 was used, which may have contained some urobilinogen, and the samples 

 were not always tested for both urobilin and urobilinogen. Hoesch {1301) 

 claimed that the synergism of Kilmmerer also oxidized urobilinogen to 

 urobilin. At that time no distinction was made between the mesobilane and 

 the tetrahydromesobilane series. 



Recently Baumgartel (193,194) has taken up the study of this 

 problem. He confirmed Kammerer's results in so far as he found that 

 a synergism of the anaerobic Bacillus rerrjicosus* (a component of 

 Kammerer's "/?. putrificus'') and the facultative anaerobe E. coli 

 was required for the reduction of bilirubin to tetrahydromesobilane. 

 Metabolites of protein putrefaction were also necessary. He estab- 

 lished the fact that the strict anaerobe was only required for the 

 formation of cysteine from protein and the reduction of cystine to 

 cysteine; this occurs in the caecum. Dehydrogenases of E. coli then 

 transfer the hydrogen of cysteine to bilirubin in the lower parts of 

 the alimentary canal. The bacterial reductases primarily add hydro- 

 gen to the pyrrole rings I and IV and then to the methene groups a 

 and c (cf. Chapter IV, Section 6.3.), also reducing the vinyl side 

 chains. Thus tetrahydromesobilane is formed. Liver enzymes, in 

 contradistinction to the bacterial enzymes, reduce only to meso- 

 bilane (cf. below). The feces of breast-fed infants lack the bacteria 

 necessary for the reduction of bilirubin, whereas these bacteria occur 

 in the feces of the bottle-fed infant, together with urobilin. The age 

 at which bilirubin disappears from the infant's feces varies widely, 

 but after the seventh month no bilirubin is found {2741). Neverthe- 

 less, the fecal urobilin excretion remains low^ in infancy and child- 

 hood {"i-l mg. at 3-11 years of age); it is still unknown whether this 

 is due to a destruction of bilirubin with formation of other com- 

 pounds, or to a slower hemoglobin catabolism. A trace of unaltered 

 bilirubin is found in normal feces {cf. also 29H9, p. 2501), the feces 

 of vegetarians containing more, since their acid reaction inhibits the 

 bacterial reduction. 



The bacterial enzyme systems are unable to reduce biliverdin to 

 bilirubin, in contrast to those of the liver {cj. Section 8.2.). Garrod 

 {9S1) reviewed the evidence showing that herbivorous animals with 

 green bile excrete less urobilin. 



* Clostridium lernicosum. 



