18 Walter H. Burkholder 



long bean (V . sesquipedalis W. F. Wight.), soybean (Glycine max Merr.). 

 kudzu vine (Pueraria hirsuta Schneid.), broad bean (Vicia faba L.), field 

 pea (Pisum sativum L. var. arvense Poir.), sweet clover (Melilotus alba 

 Desr.), and alfalfa (Medicago saliva L.). 



ETIOLOGY 



Many strains of Phytomonas phaseoli have been isolated, from time to 

 time, from various types of symptoms and from various parts of the bean 

 plant (Phaseolus vidgaris). Most of these strains have been from specimens 

 gathered in New York, but in two cases they have been from foreign 

 countries — one from Bermuda and one from Switzerland. Besides being 

 isolated from P. vulgaris, cultures have been obtained from P. lunatus 

 and P. coccineus. In all these instances the strains have been practically 

 identical, which indicates that Phyl. phaseoli is a very stable species. 



In culture the organism does change somewhat. While it still may 

 produce as vigorous a growth on agar, certain biochemical reactions in 

 culture appear to diminish though they have never been observed to be 

 entirely lost. Strains that have been grown in culture for a number of 

 years will not liquefy gelatin as rapidly as will recently isolated strains, 

 and, similarl}-, the action on milk is delayed. Consequently, in comparing 

 old and young cultures there frequently are shown minor differences which 

 would not exist if the strain had been under identical conditions previously. 



Morphology 



Phyl. phaseoli is a medium-sized rod with rounded ends, occurring singly 

 or in pairs. Filaments have never been observed in this species. Often 

 certain cells appear to be oval, but in cultures twenty-four hours old the 

 variation about the mode is not great. Such cultures, on beef-extract 

 agar (pH 6.9) and incubated at 27° C, show the following dimensions: 

 1.9 M (1-35 to 3.6/x) by 0.87 m (0.45 to 1.35/x). 



The organism is motile by means of a single polar flagellum. It is 

 Gram-negative, not acid-fast, and capsule production has not been demon- 

 strated. When grown on a medium containing dextrose a large amount 

 of gum is produced. The pathogene appears to be a fairly strict aerobe. 



Cultural characteristics 



(All cultures incubated at 27° C. unless otherwise stated) 



Beef-extract agar slants (pH 7.0). A moderate growth develops along the 

 streak within twenty-four hours. Growth becomes abundant, filiform, 

 wet, glistening, and amber yellow in color. The consistency is often 

 very watery. From appearance the cultures are not amorphous, since 

 various shades and intensities of the pigment occur within the bacterial 

 growth. 



