BACTERIA DECOMPOSING UREA 209 



belong here, as well as other spore-bearing bacteria (so-called putrefactive 

 forms), such as the anaerobic Bac. putrificus, and Bac. perfringeus. 



IV. Non-spore bearing bacteria. Bact. ureae Leube, Bad. ureae I Burri, 

 Urobact. schutzenbergii Miquel, Urobad. miquelii Beij., Urobad. jackshii Sohn- 

 gen, Urobact. beijerinckii Christ., as well as a number of common bacteria like 

 Bad. coli, Bad. prodigiosum, Ps. jiuorescens, Bad. vulgare, etc. 



A large number of spore-forming and non-spore-forming bacteria 

 were isolated from manure. 10 According to Lohnis, the urea-decompos- 

 ing power of the various urea bacteria quickly ceases when these organ- 

 isms are kept in culture. They cannot, therefore, be considered as 

 representatives of separate genera, but merely as varieties of common 

 species, like Bact. vulgare, Bact. coli, Bact. ■prodigiosum, Bad. fluores- 

 cens, Bad. erythrogenes. Most of the Urococcus species, which are dis- 

 tinguished only by degree of pigment formation and gelatin liquefaction, 

 belong chiefly to the Microc. pyogenes Rosenb. The same may be true 

 of Microc. ureae Cohn. Bad. ureae Leube, named by Miquel Urobacil- 

 lus leubii, belongs to the Bact. vulgare group; the same is true of Urob. 

 miquelii Beij. and other Urobacilli (like Urob. jakschii Sohngen). 



This assumption is justified in view of the fact that a number of 

 common soil bacteria, including various cocci, non-spore-forming and 

 spore-forming bacteria, are capable of decomposing urea. 



Sohngen 11 described two new non-spore-forming bacteria decompos- 

 ing urea in the absence of proteins. An aerobic non-spore-forming, 

 rod-shaped organism (Urob. beijerinckii), 1| by f to lp in size, was 

 found to utilize urea both as a source of carbon and nitrogen, in the 

 complete absence of other organic substances. 12 Glucose cannot be 

 utilized and may even injure the urea-splitting power of the organism. 

 Humic acid was found to have a favorable influence upon the decom- 

 position of urea. 



Viehoever 13 found that most of the common urea bacteria, such as 

 Urobacillus pasteurii, Urob. leubii and probably also Urob. maddoxii, 

 Bac. ureae II and III, Bact. ureae could be combined into one species, 

 Bac. probatus (No. GO, PI. X). 



This organism was obtained by heating some soil at 100°C, then inoculating 

 into a medium containing 1 gram K 2 HPO.i, 0.1 gram CaCl 2 , 0.3 gram MgS0 4 , 



10 Lohnis and Kuntze, 1908 (p. 32). 

 "Sohngen, 1909 (p. 207). 



12 Christensen, H. R. tjber den Einflusz der Humustoffe auf die Ureumspal- 

 tung. Centrbl. Bakt. II, 27: 337-362. 1910. 



13 Viehoever, 1913 (p. 208). 



