JONES' SOFT ROT OF CARROT, ETC. : CULTURAL CHARACTERS 249 



acid produced? Distill a flask-culture which has become acid 

 and determine whether the steam is acid to neutral litmus paper. 

 Use a large flask with a shallow layer of liquid. Collect the steam 

 in water and make tests for nature of the acid. Is it acetic acid 

 or only CO2? Boil the residue and determine whether it 

 becomes more acid on concentration. Can you identify the 

 residual acid? Is it lactic acid? 



Contrast with B. phytophthorus in +15 peptone bouillon 

 wdth from 5 to 10 per cent of ethyl alcohol added (by means of a 

 sterile pipette) after sterilization. 



Study nitrogen nutrition, reduction of nitrates, formation of 

 hydrogen sulphide, ammonia, indol. Production of enzymes — 

 starch-converting, proteolytic, cytolytic, etc. What is pectinase? 

 Try the following experiment: Inoculate the center (surface 

 only) of several agar plates and when the growth has become ^i 

 inch in diameter cut out the agar with a sterile knife in such a 

 way as to remove all of the bacterial growth without touching it 

 and transfer the agar bottom down to slices of raw carrots, tur- 

 nips, etc. If you have done the work properly there will be no 

 growth of the bacteria on the raw^ surface and yet it will rot. 

 Why? Demonstrate absence of bacteria in the decaying tis- 

 sues and describe their appearance under the microscope. 



Is the milk curd a normal cheese curd? Is gas ever produced 

 from milk? Try it in the closed end of fermentation tubes. 

 Hold checks. 



On what raw media and steamed substrata is the brown pig- 

 ment produced? What is the nature of this compound? Is it 

 a host reaction or a bacterial excretion? 



It is important to isolate the organism from carrots (natu- 

 rally rotting), from Gidding's melon rot and from Townsend's 

 calla hly rot for comparison. Do so by all means if you have 

 the opportunity, or send the material to some one who will. 

 Much additional work remains to be done on the soft-rot 

 bacteria. 



Non-nutritional Environment. — Action of heat, cold, dry air 

 (very sensitive), sunlight v very sensitive), acids, alkalies, germi- 

 cides. Behavior in vacuo, and in neutral gases such as hydrogen, 

 nitrogen, carbon dioxide. 



