18 



Donald Reddick and V. B. Stewart 



BIOLOGICAL STUDIES OF BACTERIUM TUMEFACIENS 



There are a number of biological problems connected with an investiga- 

 tion of crown-gall which are of considerable practical importance. One 

 of the writers (S) was engaged in such work. He had undertaken an exten- 

 sive series of tests designed to determine the longevity of the crown-gall 

 organism in pure and in mixed culture, and under a variety of conditions. 



These were not completed when his 

 connection with the institution was 

 severed, and there was no opportunity 

 to finish them before his untimely death 

 intervened. The data accumulated are 

 fragmentary, but their significance war- 

 rants publication at this time. They are 

 given in the following paragraphs. 



Persistence of B. iumefaciens in ster- 

 ilized soil. — In order to determine the 

 persistence of the crown-gall organism 

 in sterilized soil, the following experi- 

 ment was begun on November 10, 1914. 

 Fifteen small pots were filled with 

 loamy soil and sterilized. Five cubic 

 centimeters of a bouillon culture of 

 B. tumefaciens, four days old, was 

 added to each pot. Twelve test tubes 

 were partially filled, some with loam, 

 others with quartz or clay, and to these 

 one cubic centimeter of the culture was 

 added. After four days all pots and 

 tubes were tested to determine the 

 presence in living condition of the 

 organism (figure 4). All were then 

 placed in a box out of doors. On 

 January 2, 1915, the organism was re- 

 covered from clay, loam, and quartz. On April 14, 1915, a test of the 

 loam soil in the test tubes showed the organism to be present in a living 

 condition. Again on May 24, 1915, the organism was found to be alive in a 

 pot of loam and in a tube of quartz. The next test was made on September 

 14, 1915. The organism was not recovered from either pots or tubes. 



Persistence in unsterilized soil. — Experiments similar to the preceding 

 were instituted with clay, loam, and quartz which had not been sterilized. 

 As this was the most important series from the practical standpoint, 

 it is unfortunate that data on the outcome cannot be found among Dr. 

 Stewart's notes. 



Figure 4. crown-gall on tomato plant 



The cultures of Bacterium tumefaciens recov- 

 ered in the studies on vitality were tested in this 

 way in order to confirm identification 



