Abstract
Recent studies by Martin, 1 Winslow and co-workers 2 and Clifton 3 on the metabolic activities of bacteria indicate that the rate of metabolic activity per cell varies widely at various phases of the growth cycle. The maximal oxygen-consumption, carbon dioxide-production or ferricyanide-reduction per cell per unit time was noted near the end of the lag-period of growth and could only in part be explained by increased cell-size during the same period of growth. Total oxygen-consumption, carbon dioxide-production or ferricyanide-reduction per unit time reached maximal values near the end of the logarithmic period of growth and then decreased rapidly as the age of the cultures increased.
The present paper reports the influence of peptone- and of oxygen-concentration on the oxygen-consumption, as measured by Warburg's technic, of cultures of Escherichia coli at 37.5°C. The oxygen-consumption per cell reached maximal values during the latter part of the lag-period, over a wide concentration range of either peptone or of oxygen. The rate of growth increased slightly as the concentration of peptone was increased from 1.0 to 10% while the total crop was increased approximately 4 times. All cultures were inoculated with the same initial numbers of bacteria. The oxygen-consumption of the cultures varied widely with the age of the cultures and with concentrations of peptone or of oxygen. Typical results are reported in Table I.
The amounts of oxygen consumed per milliliter of the cultures during the first 10 hours were approximately 430 cu. mm. in 1.0% peptone, 2400 cu. mm. in 5% and 3300 cu. mm. in 10% peptone cultures of Esch. coli. A marked immediate increase in oxygen-consumption was observed in 24-hour cultures in 1.0% peptone following the addition of small amounts of concentrated solutions of peptone.
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