66 Walter H. Burkholder 



is formed when the pathogene is grown on beef-extract or beef-infusion 

 agar, and is very conspicuous in Fermi's and in Uschinsky's solution. 

 Also, on the agars the bacteria cells may be of a creamy color in young 

 cultures to a naples yellow in older ones, and in many solutions and 

 broths a yellowish sediment is formed. In dextrose broth an orange- 

 yellow pigment colors the entire medium, and one strain of the pathogene 

 produced it to such an extent that it was difficult to detect the Andrade's 

 indicator in the medium. 



Virulence. A loss of virulence, and even of pathogenicity, of the 

 organism occurs in pure culture. This was first noted when a strain 

 isolated in October, and re-isolated on November 10 of the same year, 

 showed little invasive ability on the 1st of January. For making 

 inoculation experiments, and especially cross inoculations, re-isolations 

 were made about once a month. In this way the virulence of the 

 organism was kept from waning. 



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

 10 cubic centimeters of beef-extract broth (pH 7.1), were used in this 

 experiment. To these tubes were transferred two large loops full of a 

 broth culture twenty-four hours old, and the tubes were immersed in a 

 water bath for ten minutes. The water was kept agitated and accurate 

 temperature readings were made continuously. The thermal death- 

 point appeared to vary somewhat with the strain used, from 48° to 50° C. 



Nomenclature 



The pathogene under consideration belongs to that group of bacteria 

 which produces a water-soluble green fluorescent pigment, and consequently 

 it is more or less related to all the species of that group. As far as known, 

 however, its primary characteristics do not entirely agree with those of 

 any of the previously described forms. For this reason, and from the 

 fact that the disease which it produces on the common bean (Phaseolus 

 vulgaris) is very characteristic, it is here considered as a new species and 

 the name Phytomonas viridiflava n. sp. is given to it. 



Brief description 



Phytomonas viridiflava is a non-spore-forming rod with rounded ends, 

 occurring singly or in pairs. The average size of the cells is 2.13^ by 

 0.8 lju. The organism is motile by means of one to two polar flagella. It is 

 Gram-negative, not acid-fast, and a facultative anaerobe. Capsules have 

 not been demonstrated. 



Growth on beef-extract agar streaks is good to abundant, filiform, 

 smooth, glistening, and translucent; the bacteria become naples yellow 

 with age; a green fluorescent pigment is formed on agar and on various 

 other media; bouillon becomes cloudy, with a light flocculation; liquefaction 

 of gelatin is rapid; litmus milk is cleared, and the litmus turns slightly 



