208 
Journal of Agricultural Research 
Vol. I, No. 3 
whey from curd nor the color changes were apparent in cultures of 
Pseudomonas tenuis during a period of seven weeks. One of the most 
important cultural differences between these two organisms appeared on 
gelatin plates. Bacterium aptatum is a rapid liquefier, while Pseudomonas 
tenuis showed only a trace of liquefaction in three weeks, this slight 
liquefaction occurring only on thickly sown plates and not at all in stab 
cultures. The essential difference, however, between Bacterium aptatum 
and Pseudomonas tenuis is not so much a cultural as a physiological one. 
This is shown in the ability of Bacterium aptatum to produce diseased 
spots on sugar-beet, nasturtium, and bean leaves, while Pseudomonas 
tenuis is nonpathogenic to these hosts. 
COMPARISON OF BACTERIUM PHASEOLI WITH BACTERIUM APTATUM 
When it was observed that Bacterium aptatum 1 produced diseased 
spots so readily on leaves of the bean plants, the question at once sug¬ 
gested itself as to the relation between this organism and Bacterium 
phaseoli , the cause of the well-known bacterial blight cff bean, as de¬ 
scribed and worked out by Dr. Erwin F. Smith. 1 2 The cultural charac¬ 
teristics of Bacterium aptatum were, therefore, compared with those of 
Bacterium phaseoli. As a result of this comparison it is evident that 
the two organisms are entirely different. 
Some of the characteristic differences between the two organisms are 
shown in Table III. 
Table III .—Comparison of the cultural characteristics of Bacterium aptatum and 
Bacterium phaseoli. 
Media, etc. 
Bacterium aptatum. 
Bacterium phaseoli. 
Beef agar (plate). Whitish colonies, slightly bluish in 
diffused light; medium greened. 
Agar slant. Whitish, smooth, faintly blue in trans¬ 
mitted light; medium greened. 
Potato slant 
Litmus milk. 
Thermal death point.... 
Flagella. 
Pathogenic to— 
Resistance to dry air.... 
Resistance to sunlight... 
Color in mass. 
Cream white to wood-brown; viscid; 
medium browned; no diastasic 
action. 
Alkalin reaction; slow clearing during 
seven weeks. 
47-5° to 4 8° C. 
Bipolar; one to several. 
Nasturtium, sugar beet, bean, and 
other plants. 
Few hours to several days. 
80+ minutes. 
Whitish. 
Yellow colonies, smooth, wet-shining; 
thin, distinct margins. 
Smooth, translucent, yellow; slimy 
consistency; growth without retarda¬ 
tion. 
Copious yellow slimy growth, medium 
grayed; diastasic action powerful. 
Slow alkalinity and separation of casein 
from whey. 
49-5 °C. 
Polar; one. 
Bean and lupine. 
27 days. 
30 to 45 minutes. 
Yellow. 
1 This comparison was made with Bacterium aptatum isolated from nasturtium. 
2 Smith, B. F. Description of Bacillus phaseoli n. sp., with some remarks on related species. Proc, 
Amer. Assoc. Adv. Sci., 46th meeting, 1897, p. 288-290, 1898. 
- The cultural characters of Pseudomonas hyacinthi, Ps. campestris, Ps. phaseoli, and Ps. stew. 
arti—four one-flagellate yellow bacteria parasitic on plants. U. S. Dept, of Agr., Div. Veg. Physiol, and 
Path., Bui. 28, 153 p., illus., 1901. 
- Bacteria in Relation to Plant Diseases, v. 2, Washington, D. C., 1911, p. 62. (Carnegie Inst. 
Washington, Pub. 27, v. 2.) 
