36 Walter H. Burkholder 



Saccharose broth. A cloudy growth appears in the open arm of a fermenta- 

 tion tube within twenty-four hours. The medium soon becomes acid, 

 and the reaction becomes greater with age. No other change occurs. 



Lactose broth. A light, cloudy growth appears in the open arm of a fer- 

 mentation tube within twenty-four hours. On the second day the 

 medium shows an acid reaction. From a light pink in color, it gradually 

 deepens to a distinct red. 



Maltose broth. A light, cloudy growth appears in the open arm of a fer- 

 mentation tube within twenty-four hours. A slight acidity appears on 

 the fourth day and gradually increases in intensity. No other changes 

 occur. 



Indol production. The organism does not produce indol when grown in 

 trytophane broth, as shown by the Ehrlich-Bohme test used at the end 

 of one and of four days. 



Nitrate reduction. The -organism grows well in nitrate broth, and tests 

 made at the end of two, four, and eight days with sulfanilic acid and 

 a-naphthalamine in acetic acid show no reduction of nitrates to nitrites. 



Hydrogen-sulfide production. A very light growth is obtained on Wilson's 

 medium, and in certain cases there has been no growth. Where growth 

 does occur there is no positive reaction for hydrogen-sulfide production. 

 Growth occurs in lead-acetate agar stabs with all strains tested. Certain 

 strains show a slight browning along the stab, while others remain color- 

 less. Hydrogen sulfide is not produced, or is produced only weakly by 

 certain strains. 



Chromogenesis. The organism is pale yellow in color, but the intensity of 

 the pigment may vary with the strain and the medium used. The 

 color is more intense on beef-infusion agar, and is almost absent on 

 dextrose agar. 



Oxygen relations. Although the organism ferments all the sugars tested, 

 there is no sign of growth in closed arms of fermentation tubes. In 

 shake cultures of beef-extract agar with 1 per cent of dextrose, colonies 

 appear 5 millimeters below the surface. On the whole, the pathogene 

 appears to be a fairly strict aerobe. 



Longevity and virulence. This pathogene is very resistant to adverse con- 

 ditions, and remains viable in culture for a long period of time. It has 

 been isolated from dried leaves which have been in the herbarium for 

 five years. Once in culture, it does not lose its pathogenicity or its 

 virulence to any appreciable extent. Old cultures which are very dry 

 will often yield viable cells. The organism may be recovered from bean 

 seeds infected with it and treated with dry heat at 100° C. for an hour. 

 It does not produce spores in culture, and probably does not in nature. 

 Partly protected by the bean seed, and being in a dry condition, it is 

 highly resistant to dry heat. 



Thermal death-point. Tests have not been made to determine the thermal 

 death-point, but Miss Hedges reports that it is approximately 60° C. 



