ISOLATION OF AN INHIBITORY SUBSTANCE FROM 
PLANTS 1 
W. L. Mallmann and Carl Hemstreet, Department of Bacteriology, Michigan 
Agricultural College 
INTRODUCTION 
The isolation of lytic and inhibitory substances from animal sources by various 
investigators led the writers to a study of diseased plants in order to determine 
whether or not such substances were found in association with plant pathogens. 
It seems needless to review the literature on bacteriophage since so many recent 
articles have included extended reviews. A number of investigators have found 
bacteriophage present in the intestines of man and animals in association with 
disease organisms. It is generally believed that bacteriophage develops under 
a diseased condition, adapts itself to the causative organism, and where a recovery 
results, it develops a high lytic power, causing a lysis of the causative organism. 
A survey of the available literature failed to reveal any work of this nature on 
plant diseases; hence the present work. 2 
Soft rot of cabbage was selected for study, as it was easily obtained. A cabbage 
showing soft rot was placed in a large culture dish and allowed to decompose until 
a considerable quantity of liquid material had collected. At this point, loop 
dilution plates were made in order to isolate the rot-producing organisms. As 
the plates showed practically a pure culture, several colonies were fished and 
planted on agar slants. One of these cultures was used for all the work carried 
Table I.— The effect of the cabbage-rot filtrate on different organisms a 
Culture 
Control 
Amount of filtrate added 
1 drop 
2 drops 
2 cc 
B . coli ... ... 
Do. .. 
_ 
_ 
— 
_ 
B. carotovorus ... .... 
_ 
_ 
_ 
Do........ 
_ 
_ 
_ 
B. melonis .... ..... 
_ 
— 
_, 
_ 
Do_______ 
_ 
_ 
_ 
Cabbage-rot organism... ... 
i 
± 
± 
Do__..;____ 
_ 
± 
± 
± 
a The following symbols are used in the tables: —, very strong turbidity; ±, slightly less turbidity; 
+, cloudy; ++, less cloudy; +++, nearly clear; ++++, clear. 
out. The collected liquid was filtered through a filter paper, previously impreg¬ 
nated with diatomaceous earth. The clear filtrate was passed through a Berke- 
feld filter to remove all the bacteria present. The technique used was similar 
to that recommended by d’H6relle. 3 The organism was isolated and in addition 
stock strains of Bacillus carotovorus , B. melonis , and B. coli were now inoculated 
into tubes of plain broth and incubated for one hour. Varying amounts of the 
1 Received for publication Mar. 10, 1924. 
* This work was done in the spring of 1922. Since writing this paper, the following article has appeared: 
GERRETSEN, F. C., AND OTHERS. DAS VORKOMMEN EINES BAKTERIOPHAGEN IN DEN WURZELKNdlA- 
uhen DER LEGUMINOSEN. Centbl. Bakt., (II) 60: 311-316, illus. 1923. 
^d’Herelle, F., the bacteriophage, its r6le in immunity. ... Tr. by G. H. Smith. 287 p., 
illus. Baltimore. 1922. 
Journal of Agricultural Research, 
Washington, D. C 
( 599 ) 
Vol. XXVIII, No. 6 
May 10, 1924 
Key No. Mich.-14 
