SCHUSTER'S GERMAN POTATO ROT. 

 OBSERVATIONS BY SCHUSTER. 



In 1912, Schuster described a polar-flagellate, green-fluorescent schizomycete from 

 rotting potato tubers obtained from six different localities in Germany, as Bacterium xantho- 

 chlorum n. sp., and asserted it to be the cause of the disease. 



The organism when inoculated also blackened, it is said, and destroyed leaves and 

 stems of Vicia faba, and rotted other plants. It is by no means as active an organism on 

 potato as Bacillus phytophthorus. It does not attack the stems of potato, and from 

 Schuster's own account it seems to be a rather weak parasite except at high temperatures 

 (most active, he said, at 36.5 to 38 C.), or under other abnormal conditions, e. g., heavy doses 

 of the bacteria, under bell-jars in very moist air. In dry air at room-temperatures the 

 inoculations soon dried out and the tuber as a whole remained sound. At times it showed 

 a decided tendency to occupy the vessels, e. g., in Vicia faba, and in early stages of the 

 tuber-rot of the potato. All of Schuster's inoculation experiments appear to have been 

 made under abnormal conditions, i. e., in laboratory rooms, under bell-jars, etc., in a 

 saturated air. 



His Bact.xanthochlorum causes a slow, gray or yellow, wet-rot of the tuber, often proceed- 

 ing from the vascular bundles in or out, and from the margin of this rot it is easy to isolate 

 pure cultures. Often the tubers are not much injured on the surface. The rotted parts 

 smell of ammonia. 



It is not able to enter the potato tuber through the opened lenticels [another indication 

 of weak parasitism]. In general it is a wound parasite, but it may enter, it is said, the green 

 parts of Vicia faba through stomata. 



It was inoculated successfully by Schuster into carrot roots, young tobacco stems (30 

 to 36 C.), Lupinus nanus douglasi, Physalis alkekengi, and Campanula raphunculus. 

 Fodder beets, sugar beets, yellow lupins, tomatoes, and pelargoniums proved insusceptible. 



This organism, according to Schuster, has the following morphological and biological 

 characteristics: 



As a rule it is actively motile, but once a non-motile strain was isolated [this may have been 

 some related organism]. The flagellum is polar. Sometimes two flagella are present, rarely three 

 occur. The straight ones are 4.5 to 6/u long, i. e., two to three times the length of the rod. They 

 stained poorly with carbol-fuchsin, but readily with Pepler's stain followed by carbol gentian violet. 

 Hinterberger's modification of Van Ermengem's stain was also used successfully. At temperatures 

 under 5 C. and above 40 C. no flagella formation could be detected. In bouillon motility was 

 observed for 1 8 days, but on potato at 20 C. it ceased after one day. On agar-streak-cultures motil- 

 ity ceased after one day at 37 C. but was visible after 20 days at 20 C. 



Under normal conditions of growth the organism is a slender rod with rounded ends, i .5 to 

 3X0.75^, occurring for the most part singly or in pairs. It stains readily with basic anilin dyes but 

 not by Gram. 



On agar at 36 C. and at higher temperatures, long threads are produced within 24 hours. These 

 long rods may show constrictions, but do not afterwards separate into short elements. Short, plump 

 rods were observed at 2 C. 



Spores do not occur. Involution forms (plasmoptyse) occur. Pseudozoogloeae occur. 



The yellowish-green fluorescent pigment is soluble in water. After cultivating this organism on 

 potato agar, carrot agar, or wheat-decoction agar for 3 months the color disappeared, but always 

 could be restored by inoculation into alkaline bouillon, even after 6 months of colorless growth on the 

 potato agar. 



Glycogen was detected in bouillon-cultures at the end of the second day using potassium 

 iodide. 



No acids are produced; the cultures are always alkaline [see below]. Ammonia, methylamin, 

 and trimethylamin occur. 



Trypsin, amylase, tyrosinase, and a hemicellulase are produced. A soluble toxine active on the 

 protoplasm is also produced. 



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