THE ROLE OF THE HYDROGEN-ION CONCENTRATION 
ON THE DEVELOPMENT OF PIGMENT IN FUSARIA 1 
By Christos P. Sideris 2 3 
Agricultural Experiment Station f University of California 
INTRODUCTION 
The present investigations are con¬ 
cerned with the influence of the 
hydrogen-ion concentration of the 
substratum on the development of 
pigment by Fusaria. 
The production of pigment has been 
studied by many investigators and 
this phenomenon has been used as a 
character for the taxonomic classifica¬ 
tion of a number of species. Wollen- 
weber {14, 15), z Milburn (5) and 
Bessey ( 1) observed that Fusaria 
produced different colors if grown on 
either carbohydrates or proteins, each 
reaction being accompanied by special 
colors which changed with the change 
of reactions of the substratum. The 
chemical nature of the pigment has 
probably not been studied, nor the 
factors which govern its development 
and intensity. The pigment, which 
is often observed on Fusaria grown in 
their natural habitat, is pink, the 
intensity and hues varying with the 
substratum. 
CULTURAL METHODS 
The methods employed for the study 
of the influence of different hydrogen- 
ion concentrations on the development 
of pigment by Fusaria, consisted in 
growing the organism or organisms in 
culture media at different initial P H 
values and observing the color and 
intensity of the pigment produced 
therein. As the studies were concerned 
with the development of pigment at 
definite hydrogen-ion concentrations, 
the use of an apparatus which would 
permit frequent determinations of the 
hydrogen-ion concentration of the 
culture solution became essential. The 
apparatus, used by the writer {10) in 
certain preceding studies was adopted. 
It provides for frequent determina¬ 
tions of the hydrogen-ion concentra¬ 
tion and for the introduction of various 
volumes of adjusting reagents, for the 
maintenance of a fairly constant 
reaction, under relatively aseptic condi¬ 
tions. 
The writer {11) as well as others found 
that Fusaria are capable of changing 
the reaction of their culture media 
either by increasing or decreasing the 
hydrogen-ion concentration, the direc¬ 
tion of the changes depending on (a) 
the initial P H value of the culture 
solution, ( b) the chemical nature of the 
nutrient substance, and (c) the age of 
the culture. On account of this 
ability of Fusaria to change certain 
of the initial P H values of their cul¬ 
ture media, the different cultures in 
the experiment were treated in two 
different ways—some were adjusted 
to definite hydrogen-ion concentra¬ 
tions with volumes of 0.2 normal HCl 
or NaOH, and others were left un¬ 
adjusted. The purpose of this treat¬ 
ment was to distinguish between the 
influence of the hydrogen-ion con¬ 
centration of the culture media and 
that of the hydrogen-ion concentra¬ 
tion of the microorganism, namely, 
that which is produced by the organ¬ 
ism and changes the initial reaction 
of the culture solution during the 
assimilation of nutrient substances on 
the development of pigment. 
For the growth of the different 
organisms and the development of 
pigment, dextrose solutions in com¬ 
bination with certain inorganic salts 
were used. They were mixed in the 
following proportion: Distilled water 
1,000 c. c., dextrose 20 gm., MgS0 4 
2.12 gm., Ca(N0 3 ) 3 20.71 gm., KH 2 P0 4 
1.36 gm., and Fe(N0 3 ) 3 1 c. c. of a 5 
per cent solution. Half-liter portions 
of this solution were adjusted to 
definite hydrogen-ion concentrations 
by the addition of appropriate reagents 
before being placed in the apparatus 
mentioned, and sterilized. Solid cul¬ 
ture media were also prepared by add¬ 
ing to the above 2 per cent agar-agar. 
1 Received for publication July 26, 1924; issued August, 1925. 
2 Now at the University of Hawaii, Honolulu, Hawaii. 
3 Reference is made by number (italic) to “Literature cited,” p. 1019. 
Journal of Agricultural Research, 
Washington, D. C. 
(ion) 
Yol.XXX, No. 11 
June 1, 1925 
Key No. Calif.-39 
