Apr. 15, 1921 
135 
Bacterial Spot of Tomato 
cultures heavy growth in the closed arm and abundant gas formation 
had occurred. 
After 40 days, titration with phenolphthalein showed that there was 
very little change in acidity. The saccharose and mannit cultures were 
slightly more acid than their controls, the maltose culture was unchanged, 
the dextrose and glycerin cultures were slightly less acid than their 
controls, and the lactose culture was quite decidedly less acid. All the 
Bacillus coli cultures showed greatly increased acidity. 
To determine more accurately the changes in true acidity in these 
media, recourse was had to the sulphone-phthalein indicators as advocated 
by the Society of American Bacteriologists (2). Three series of four test 
tubes each of the six media described above were prepared. One series 
contained brom cresol purple, one contained brom thymol blue, and the 
third contained phenol red. The indicators were used in a concentration 
of 0.0016 per cent. The characteristics of the three indicators are pre¬ 
sented in Table I. 
Table I .—Changes in acidity as shown by sulphone-phthalein indicators 
Indicator. 
Full acid 
color. 
Full alkaline 
color. 
Sensitive 
range. 
Brom cresol purple.. 
Yellow. . .. 
...do. 
Purple.... 
Blue. 
Ph. 
5.2 to 6.8 
6.0 to 7.6 
6.8 to 8.4 
...do. 
Red. 
Thus these indicators should serve for P H values between 8.4 and 5.2, 
but our standards made up according to Sorensen 1 showed that the 
usable range was more restricted. The media were adjusted to a 
slightly alkaline reaction of about P H 7-5 as indicated by the blue 
shade of brom thymol blue and the yellowish red with phenol red. This 
gave a full alkaline purple with brom cresol purple. These tubes were 
sterilized, and two of each set of four were inoculated with the bacterial 
spot organism, one was inoculated with Bacillus coli, and one tube was 
held as a control. All were incubated at 22 0 C. 
Vigorous growth occurred in all the cultures. A surface pellicle and 
precipitate were formed in every case. Observations were made at the 
end of 2 days, 7 days, 14 days, and 43 days. In all the cultures of the 
tomato organism containing brom cresol purple and brom thymol blue 
there was no change in color, while in the cultures containing phenol red 
a brighter red color appeared within 14 days and all were uniformly 
brighter red at the end of 43 days. The lactose cultures were the first 
to show this red. All the Bacillus coli cultures became yellow. The 
controls remained unchanged. 
I SORBNSBN, S. P. I*. UBBR DIB MBSSUNG UND BBDBUTUNG DBR WASSBRSTORRIONBN-KONZBNTRATION 
BBi biologischbn prozbssbn. In Ergeb. Physiol., Jahrg. 12, p. 393-532. 12 fig. 1912. Literature, p. 
394-398. 
29669°—21-4 
