MICHIGAN ACADEMY OF SCIENCE. 
147 
THE ASSOCIATION OF PSEUDOMONAS RADICICOLA WITH 
BACILLUS RAMOSUS. 
WALTER G. SACKETT. 
In preparing and developing liquid cultures of nodule forming bacteria 
in such quantity as is required when several hundred .pounds of seed 
are to be inoculated, it not infrequently happens that during the 
growth of the germs, there is set up in the medium a fermentation not 
typical of Ps. radicicola, but one which is clearly an off fermentation. 
Occasionally we have a vigorous gas production accompanied by an 
abundant formation of froth on top of the culture, giving every indica¬ 
tion of a yeast at work, and an examination of such material will, in 
nearly every case, show a torula form to be present. More frequently, 
however, there develops a disagreeable, sour odor similar to putrefying 
water from a vase of flowers. Here, instead of the yeast we usually 
find a large, rather thick, motile bacillus, apparently of the B. ramosus 
type. Before going any farther, there are two questions which naturally 
suggest themselves; first, do these contaminations, for such they are, 
have any influence upon the growth of the nodule-forming bacteria, 
and if so is it to be regarded in the light of antagonism or mutualism, 
or in other words, is this association detrimental, neutral or beneficial 
to the growth of Ps. radicicola ? The second query is this: if by ex¬ 
ercising every precaution in our laboratory technique to keep out these 
contaminations, we still meet with them, how much greater is going 
to be the off fermentation when the rearing of these pure cultures is 
intrusted to the farmer whose knowledge of bacteriological methods is 
practically nil and whose facilities for sterilizing utensils and media 
are very limited. 
Considerable has been said here and there bearing upon this ques¬ 
tion in a more or less general way and intimating that possibly the 
reason a culture failed to give the sought for inoculation of the roots of 
legumes was because other germs got into the cultures and in some 
way rendered it worthless. And then again, we can pick up literature 
in which are given directions for preparing these cultures and in nearly 
every instance the operator will be cautioned about keeping out dirt, 
for it is possible that other bacteria may exert a detrimental influence. 
But when we are pinned right down to the question, “Do you know 
that any of these germs are antagonistic towards Ps. radicicola?” 
we find that specific experimental data is sadly wanting. The import¬ 
ance of this question from a practical standpoint is so obvious that I 
can pass it by with mere mention for upon it may depend the success 
or failure in getting an efficient inoculation of a whole season’s crop 
and with clover seed selling at from eight to ten dollars per bushel and 
alfalfa considerably higher, the farmer can not afford to waste many 
pounds of seed on a worthless culture. 
