CHAPTER II. 
GENERAL PHYSIOLOGY OF BACTERIA-THE EFFECT 
OF ENVIRONMENT ON BACTERIA. 
A. 
Rate of Reproduction. 
I. 
Light and Electricity. 
B. 
Motility: Rate of Motion. 
J. 
Gravity, Osmotic Pressure, Agita- 
C. 
Sporulation: Germination of 
tion and Chemotaxis. 
Spores. 
K. 
Enzymes, Toxins. Ptomains. 
D. 
Longevity. 
L. 
Pigments. 
E. 
Moisture: Desiccation. 
1. Photodynamic. 
F. 
Oxygen. Aerobiosis and Anaero- 
2. Phosphorescent. 
BIOSIS. 
3. Fluorescent. 
G. 
Temperature. 
4. Chromogenic. 
1. General. 
M. 
Symbiosis, Antibiosis, Commensal- 
2. Cold. 
ism. 
3. Heat. 
N. 
Media— Composition and Reaction. 
H. 
Heat Production. 
0. 
Growth in Animal Body. 
A. RATE OF REPRODUCTION. 
One of the striking characteristics of the Bacteriacese is their rapidity 
of reproduction. Among the most actively growing types of bacteria, 
as, for example, the cholera vibrio, successive generations may appear 
at intervals as frequent as every fifteen minutes when the environmental 
conditions are most favorable; that is to say, ninety-six generations 
are theoretically possible in twenty-four hours. ^ If this rate of repro- 
duction could be maintained for one day only, the progeny of a 
single organism would number- approximately (8 X 10^^). Fortunately, 
Nature imposes many restraints which limit the number of bacteria. 
The rapid accumulation of waste products, the exhaustion of nutrient 
material, and the enormous death-rate in culture media even after a 
comparatively few hours' growth, together with other factors restrict 
development to such a degree that the actual number of living descen- 
dants of bacteria in cultures or in Nature falls far short of the theoretical 
number. Many bacteria develop more slowly than this, however. 
They may require hours or even days to arrive at maturity. The 
tubercle bacillus, for example, grows comparatively slowly in artificial 
media (where such observations are of necessity made), and the fre- 
quency of septation, even in the most rapidly growing bacteria, is 
greatly affected by environmental factors. 
Generally speaking, when nutritional conditions are favorable, the 
rate of reproduction is influenced by temperature, growth being most 
rapid when the temperature is optimum for the organism, less rapid 
when the temperature exceeds or falls below this point. 
> Buchner, Longard und Riedlin: Centralbl. f. Bakteriol., 1887, 2, I. 
2 See I^endall: Civilization and the Microbe, 1923, p. 20. 
