GENERAL BACTERIAL METABOLISM 67 
relatively very great in comparison with their volume, would require 
much more material for energy purposes than for structural purposes. 
For example, the total surface area of 1,000,000 average-sized cocci 
(each 1 micron in diameter) would be approximately 3.1416 sq. mm.; 
the weieht of these organisms, assuming the specific gravity to be 
1.03 (which is reasonably accurate), would be about 0.00054 mg. 
The combined surface of all the cocci in an actively growing broth 
culture of such organisms would be very considerable. It must be 
remembered, however, that these figures do not carry any specific 
basis for measurement of bacterial activity in terms of chemical or 
l)hysical phenomena; they merely express in a very general manner the 
physical basis for the apparent disproportion observed between the 
size of bacteria and the amount of change they induce in their environ- 
ment. 
Quastel and his associates' have shown that fully mature bacteria, 
washed free from cultural media, will bring about certain chemical 
transformations that the active cultures fail to accomplish. Such 
bacteria are called "resting bacteria." 
The energy phase commences theoretically when the cell is morpho- 
logically complete, and it is a continuous process which ends only with 
the death of the cell. It may be reduced to a minimum when the cell 
enters upon a latent state of existence, as in spore formation; it is 
greatest when the organism is growing in a favorable medium at the 
optimum temperature, and it is restricted proportionately when 
environmental conditions become unfavorable. 
The life-history of a culture in which innumerable bacteria are 
growing cannot be sharply divided into the anabolic and catabolic 
phases. During the first few hours after inoculation, however, the 
anabolic aspect predominates; later the catabolic aspect predomi- 
nates. Thus, colon bacilli inoculated into glucose broth fermenta- 
tion tubes do not produce gas in visible amounts during the first few 
hours of incubation, although the medium gradually becomes turbid, 
due to the rapid multiplication of bacteria. Somewhat later gas 
formation is observed, and it then proceeds with considerable rapidity. 
The production of gas is indicative of a period of great vegetative 
activity in which large numbers of mature colon bacilli utilize the 
glucose for their energy requirements. Still later the production of 
gas ceases, the activities of the organisms diminish, and the culture 
finally dies out as waste products accumulate in sufficient amounts. 
According to Michaelis and Marcora^ this state is reached when the 
hydrogen-ion concentration of the medium reaches 1 X 10'^ N. It is 
significant that this is almost exactly the hydrogen-ion concentra- 
tion of the dihydrogen-phosphates. Clark'' has corroborated this 
statement. 
1 Biochem. Jour., 1925, 19, 304, 645, 652. 
2 Ztschr. f. Immunitatforsch., orig., 1912, 14, 170. 
3 Jour. Biol. Chem., 1915, 22, 87, 
