50 Walter H. Burkholder 



formed, nevertheless, in Uschinsky's solution, and to a less extent in 

 Fermi's solution. The cultural characteristics of this pathogene agree 

 very closely with those of other members of the green-fluorescent group. 



Oxygen relations. The oxygen relationship of this organism varies with 

 the strains tested. Certain strains always appear to grow in the closed 

 arms of fermentation tubes in dextrose and in saccharose broth, while 

 other strains vary in this character. In shake agar cultures in which 

 a beef-extract agar with 1 per cent of dextrose was used (pH 7.0), one 

 strain did not produce colonies more than 3 millimeters below the 

 surface, while in other strains colonies were found as deep as 3.5 centi- 

 meters below the surface. One strain isolated from bean pods collected 

 in Switzerland had the largest colonies, and the greatest number of 

 them, from 6 to 7 millimeters below the surface. 



Longevity. The pathogene, while it frequently does not make a good 

 growth on the various agars, is a hardy organism and does not readily 

 die in pure culture. Several cultures on beef-extract agar kept at a 

 temperature of 3° to 6° C. lived for fifteen months. At the end of that 

 time, subcultures proved to be very virulent when inoculated into bean 

 seedlings. 



Thermal death-point. Test tubes of a uniform thickness, and containing 10 

 cubic centimeters of a beef-extract broth, were used in these experiments. 

 Two lots of broth were used at various times, having, respectively, a 

 pH value of 6.9 and 7.0. These tubes were immersed in a water bath 

 for ten minutes. The water was kept agitated, and accurate temperature 

 readings were made continuously with a certified thermometer. From 

 a number of such experiments it was determined that the thermal death- 

 point was approximately 49° C. 



Brief description 



Phytomonas medicaginis var. phaseolicola is a non-spore-forming rod with 

 rounded ends, occurring singly or in pairs. The cells measure 1.35 to 

 3.6m by 0.9 to 1.2fx. Filaments are often produced. The organism is 

 motile by means of a single polar flagellum. It stains readily with carbol 

 fuchsin, gentian violet, and Loeffler's methylene blue, showing granules 

 which often are bipolar. It is Gram-negative, not acid-fast, and a faculta- 

 tive anaerobe. 



The colonies on nutrient agar are white to colorless, slow- to moderate- 

 growing, concentrically ringed, with edges slightly undulate; gelatin 

 colonies are slow-growing, circular, raised, and somewhat wrinkled; agar 

 streaks are of moderate growth, colorless to white, flat, glistening, trans- 

 lucent, and butyrous at first but later brittle; in nutrient broth a cloudy 

 growth occurs within twenty-four hours and a pellicle is formed; litmus 

 milk becomes an intense blue, with no peptonization; a small amount of 

 acid is produced in dextrose and in saccharose broth, but none in lactose 



