ON CARBOHYDRATE CONSUMPTION BY 
AZOTOBACTER CHROOCOCCUM 
E. R. ALLEN 
Formerly Associate in Biochemistry, Washington University School of Medicine 
and Visiting Investigator, Missouri Botanical Garden 
In a previous paper (Allen, '19) devoted mainly to the study 
of the cause of beneficial action resulting from mechanical agi- 
tation of Azotobacter solution cultures, the defects of existing 
experimental methods for the study of the physiology of this 
organism were pointed out. The present report covers a con- 
tinuance of these studies aimed at the following improvements: 
(1) renewal of the energy source in the cultures; (2) simultaneous 
determinations of nitrogen and of residual carbohydrate at short 
intervals; and (3) mechanical improvements. 
The object of the first of these improvements was, of course, 
to produce heavier growths in the cultures and therefore more 
marked changes in the amounts of metabolic products, thus 
increasing the reliability of the measurements of such changes. 
In view of the theoretical considerations of Duclaux (98-00) in 
regard to the rate of inerease in the number of cells, we were jus- 
tified in expecting a mounting rate of total physiological activity 
as growth proceeded, until the normal rate of development was 
checked by the accumulation of unfavorable by-produets. 
The method of renewal of energy-supplying material has been 
used, for example, with marked success by Bonazzi (19) in his 
investigations of the organisms of nitrification. 
'The second improvement was designed to furnish a more com- 
plete picture of growth processes of Azotobacter than is obtainable 
by the determination of one, or even two, metabolie products at 
the end of an arbitrarily chosen incubation period. Unfortu- 
nately, the ““micro” determination of carbohydrate and nitrogen 
on the same sample proved more diffieult than was expected, and 
had to be postponed for the time being. The present work, 
therefore, lacks this improvement over that reported previously. 
The third improvement was to facilitate experimental manip- 
ulation and possibly obtain even better results from mechan- 
ical agitation. The type of agitation decided upon was a slow 
ANN. Mo. Bor. GARD., Vor. 7, 1920 (75) 
