29 



a large amount of gas, it seemed also to lose the power to form 

 anything but C0 2 . B. prodigiosus I usually failed to produce 

 gas in 1/ dextrose, 1,5 2 | being more favorable. 



Oxygen and temperature relations. All of this group 

 are facultative anaerobes, but grow without pigment in the absence 

 of oxygen. Only B. ki lien sis and B. ruber indicus produce 

 pigment at 37 C, although all are able to grow at that temperature. 



Indol production, nitrate reduction, odor. No 

 indol is formed by the members of this group. Nitrate is reduced 

 to nitrite in each case and often to free gas. The trimethylamine 

 odor is often present in cultures of the Prodigiosus group, and a 

 strong fecal odor is characteristic ofB. plymouthensis, B. pro- 

 digiosus V, and VIII. 



B. ruber indicus only is said to be pathogenic for labora- 

 tory animals. 2 ccm of a 48 hour bouillon culture inoculated intra- 

 peritoneally killed a mouse in 48 hours. Unfortunately I was unable 

 to make an autopsy. 20 ccm of a 48 hour agar suspension failed 

 to produce any effect upon a guinea pig 1 ). 



b) Growth and pigment on special solid media. 



The earlier investigators of red chromogenic bacteria, Ehren- 

 berg (26), Fresenius (27), and Cohn (30), concerned them- 

 selves chiefly with the systematic position of B. prodigiosus; Erd- 

 mann (28), and Schroeter (29) worked with the chemical nature 

 of the pigment; Schottelius (35) was the first to pursue ecolo- 

 gical studies upon the pigment production, without, however, much 

 attention to the composition of the cultural media. His conclusions 

 as to the conditions necessary for pigmentation were 1) a sufficient 

 supply of atmospheric air, 2) a suitable temperature. Wasser- 

 zug (37) experimented upon the effect of alkaline and of acid media, 

 obtaining colorless races in alkaline bouillon. K uebler (38) repeated 

 Wasserzug's procedure , but contradicted him and confirmed 

 Schottelius in asserting the non-permanency of white cultures 

 obtained by high temperature and alkaline media. 



The next important paper on the subject was that of Gale- 

 otti (15), who studied eight chromogenic organisms, among them 

 B. prodigiosus, L us tig's "red bacillus", and B. lactis ery- 

 throgenes. He found that B. prodigiosus gave less pigment 

 in liquid media than in solid, but that this was not due, as Wasser- 

 zug had thought, to lack of oxygen, since an atmosphere of pure 

 oxygen produced no better chromogenesis. He decreased the amount 

 of peptone in the agar, and inferred that a scarcity of proteid did 

 not prevent pigment production. B. prodigiosus was the only 

 organism of his series in which pigment production could be impeded 



1) Subcutaneous inoculation of 2 ccm. 48 hr. agar slant culture, suspended 

 in 5ccm 0,85 % Nacl solution, causes illness in rabbits. A large abscess forms 

 at the site of inoculation, from which a vigorous and pigmentforming culture of 

 B. ruber indicus was isolated at the end of two weeks. Abscesses are also 

 formed by B. prodigiosus 1 and VII, B. rutilus (n. sp.) , and B. amylo- 

 ruber (n. sp.). Further investigations upon the pathogenicity as well as upon 

 the agglutinative properties of these organisms are in progress. 



