BACILLUS PROTEUS GROUP 395 
do not liquefythis medium. The last, Proteus zopfii, exhil)its negative 
geotropism on slanted solid media. It is now recognized that cultures 
of B. proteus may gradually lose their gelatin-licjuefying power after 
prolonged cultivation, so that a cultural transition from B. proteus to 
B. zenkeri may be observed in the laboratory. A distinction between 
the three types is no longer made. It is not determined whether B. 
zopfii is a separate variety of B. proteus. Practically all proteus bacilli 
fail to ferment mannose as well as mannitol. 
The organisms grow vigorously in milk, causing slight acidification 
and peptonization: The development in broth is equally vigorous; 
acid and gas are produced in glucose and saccharose broths.^ Neither 
acid nor gas is formed in lactose broth.- 
Proteus bacilli grow slowly at 0° C.^ and at temperatures not exceed- 
ing 43° to 45° C. The optimum temperature is about 25° C. but 
development is rapid at 37° C. Strains obtained from putrefying 
organic matter are tolerant of considerable degrees of alkalinity^ 
and acidity;^ those from the human body are somewhat less tolerant. 
The growth of B. proteus at low temperatures is of considerable prac- 
tical importance; several cases of ptomain poisoning have been at- 
tributed to foods decomposed by this organism at the temperature 
of the ice-box. The resistance of the organisms to heat is not great. 
According to Meyerhof,*^ an exposure of twenty-five to thirty-five 
minutes at 54° C, five to ten minutes at 56° C, and of one-half a 
minute at 60° C, kills them. Their resistance to disinfectants is 
similar to that of B. coli. 
Products of Growth— (fl) Chemical.— Froteus bacilli decompose 
proteins and protein derivatives energetically. The following sub- 
stances have been detected among the cleavage products: trimethy- 
lamine, betain, phenol, hydrogen sulphide;^ from the decomposition of 
casein, deuteroalbumose, peptone, mono- and diamino-acids (histidin 
and lysin), tyrosin, indol, and skatol* An extensive liberation of 
ammonia takes place in protein media free from sugars.^ Ammonia 
is also formed from the proteins of milk, but more slowly, and in 
smaller amounts. ^° Carbon dioxide and hydrogen (H:C02 = f) ^re 
formed in glucose and saccharose broths, together with lactic acid 
and small amounts of acetic and formic acid. Lactose is unfermented." 
1 Theobald Smith: Fermentation Tube, Wilder Quarter Century Book, 1893, p. 2i:B. 
- The bacilli may gradually lose their ability to ferment saccharose; strains which 
do not ferment this sugar may be mistaken for paratj-phoid bacilli, particularly if the 
gelatin-liquefying power disappears simultaneously. The very considerable production 
of ammonia in sugar-free broth, however, readily distinguishes the proteus bacilli. 
Kendall, Day and Walker: Jour. Am. Chem. Soc, 191.3, 35, 1231. 
s Levy: Arch. f. offentl. Gesundhpf. in Els. Lothr., 1895, 16, No. 3. 
* Deelman: Arb. a. d. kais. Gesamte, 1897, 13, 374. 
6 Fermi: Centralbl. f. Bakteriol., 1898, 23, 208. 
6 Centralbl. f. Bakteriol., 1898, 24, 18. 
' Emmerling: Ber. d. deut. chem. Gesell., 1896, 29, 2721. 
8 Taylor: Ztschr. f. physiol. Chem., 1902, 36, 487. 
9 Kendall, Day and Walker: Jour. Am. Chem. Soc, 1913, 35, 12.32. 
■n Ibid., 1914, 36, 1945. 
" Theobald Smith: Fermentation Tube, Wilder Quarter Century Book, 1893, p. 213. 
