36 
North Carolina Agricultural Experiment Station 
It will be seen in the first place that B. carotovorus and B. glycinenm are 
able to ferment all of these sugars with the formation of acid. The former 
attacks all vigorously so that the characteristic final reaction is attained 
within a few days. The latter ferments dextrose and saccharose quite vigor¬ 
ously but requires a longer period of time to reach this ultimate point, and there 
is a reversal of reaction with lactose and glycerine. None of these sugars are 
attacked by B. campestre. B. tabacum, B. angulatum and B. sojae are able to 
ferment only dextrose and saccharose. 
Further, very marked differences exist in rates of fermentation by these 
forms as shown when B. carotovorus is contrasted with any of the others. In 
general, the formef* will reach its final reaction within three days, whereas five 
to nine days are required for the others. Nearly all of this change with B. 
carotovorus will have occurred within the first 24-hour period, and in this re¬ 
spect this organism is like the pneumococci, streptococci and the colon group. 
The type of fermentation produced by the others, which is apparently uncom¬ 
mon among animal pathogenic forms, results in a slow, progressive increase in 
acidity. Again, B. carotovorus is seen to require a minimum carbohydrate 
concentration between 0.1 and 0.3 per cent and amounts up to 2 per cent have 
no further effect upon the level of the final pH concentration. The minimum 
concentration of sugars for the others lies between 1.0 and 2.0 per cent under 
the same experimental conditions. At a concentration of 1 per cent of dextrose 
or saccharose, there is seen with these other forms, to be a reversal of reaction, 
beginning on about the fifth day, by which time the reaction will have changed 
from an initial pH of T.2-7.4 to pH 6.0-6.4. Forty-eight to seventy-two hours 
with 2 per cent dextrose or saccharose is sufficient time for an increase in acid¬ 
ity to this same point with these same organisms. This reversal of reaction 
is a phenomenon which has recently been investigated by Ayers and Rupp (3) 
and is due as they explain, not to the formation of ammonia, but to the fer¬ 
mentation of organic acids to carbonates. The simultaneous fermentation of 
the sugar and of the organic acids, as pointed out by them, does not decrease 
the value of sugar fermentations for diagnostic purposes, but should lead to a 
broader conception of the problem. In the present studies, the reversal of re¬ 
action with 1 per cent and less of sugar and not with 2 per cent may be taken 
to indicate that for these organisms it is associated as a casual condition with 
insufficient fermentable sugar to permit the attainment of the characteristic 
level of acidity. The carbon metabolism of B. carotovorus is manifestly quite 
different from that of B. tabacum, B. angulatum, B. glycineum and B. sojae. 
Whether plant patliogenes will be found by subsequent investigations to con¬ 
form to a number of distinct types, such as have been noted by Berman and 
Rettger (4), remains to be determined. They found that B. coli and Proteus 
vulgaris, which represent one type, ferment glucose rapidly with the forma¬ 
tion of large amounts of acid. Such appears to be the case with B. carotovorus. 
B. subtilis, representative of another type, they found to attack glucose slowly, 
as is the situation with B. tabacum, B. angulatum, B. sojae and B. glycineum. 
B. subtilis utilized both carbohydrate and protein at the same time, a condi¬ 
tion contrary to the common belief, that when both utilizable carbohydrate 
and protein are present in a medium, there is a “sparing action” of the sugar. 
B. cloacae, a third type, formed very little acid since the products of fermen¬ 
tation of glucose and lactose w T ere largely carbon dioxide and hydrogen. It 
appears unlikely that B. campestre is of this type, since there was no evidence 
