544 Bulletin 167 



were made repeatedly after incubation periods of various dura- 

 tion. The diphenylamine test for nitrates (32:340) gave a 

 positive reaction on cultures of all strains except XX X\ I. 

 (Compare 19:152-154). 



4. Indol. — Indol was not detected in broth cultures of any 

 strain on the second or tenth day. The 10 cc. cultures were 

 tested with ten drops of chemically pure sulphuric acid and one 

 cc. of .02% sodium nitrite solution. Xo reaction appeared at the 

 end of ten minutes or after warming. (3:33). 



5. Temperature relations. — The optimum temperature for 

 all strains was found to be in the neighborhood of 25 ° C. The 

 thermal death point was approximately determined in the pre- 

 liminary studies to lie between 49 and 55 C. The minimum 

 temperature for growth was below 3 C. except for strain CX\ 

 which did not develop below 5 C. This strain showed growth 

 at 37° C. All others failed to develop at that temperature and 

 eighteen days exposure was fatal to them. Luxwolda (18) 

 states that B. fluorescens liquefaciens develops remarkably fast 

 at low temperature (3 to 5° C). 



f>. Acids and alkalies. — A small amount of acid was pro- 

 duced in dextrose nutrient broth and indications of acid were 

 also observed in nutrient broth containing lactose, sucrose, and 

 glycerin. Titrations were made in hot solution with X/20 

 sodium hydroxid against phenolphthalein after 1. 2. 4. 10, and 

 20 days incubation. A trace of acid from proteid decomposi- 

 tion was observed with some of the strains in the sugar free 

 bouillon series. 



Hydrogen sulphid. — Tubes of nutrient broth were pre- 

 pared in the usual way and, after inoculation, a strip of filter 

 paper moistened with lead acetate solution was suspended above 

 the culture in each tube. The paper in cultures of strain XVI 

 began to blacken at five days showing hydrogen sulphid pro- 

 duction. In ten days the papers in cultures of strains CXL, 

 CXLI, CXLII, CXLIII, CXLVI, XVI, LIV, CXV, showed 

 positive reactions, which in tin- cases of the last two strain.-, 



