A Note on the Respiration of Bacillus coli . ∗

Abstract

The respiration of prepared aliquots of a suspension of Bacillus coli has been used extensively in this laboratory for comparing the calibration-constants of different Bareroft-Haldane differential manometers and their culture-vessels. The great accuracy of the observations has brought to light an hitherto unreported phenomenon in the oxygen-absorption of this organism.

The suspension of bacteria grown on agar for 18 hours was washed off with 10 cc. of broth, filtered through sterile cotton, and 0.1 cm. of the resulting suspension was placed in the vessel of the respirometer after further diluting it with 10 cc. of broth. The oxygen-uptake was observed at this final dilution at 37°C. Plating showed the cultures to be pure at the end of the experiment.

It was found that the rate of oxygen-uptake increased logarithmically, as would be expected, until the culture reached the age of about 3 hours and 40 minutes. At this time a new rate was initiated. The course and magnitude of this change is seen in Table I and plotted on Fig. 1. Many similar experiments were carried out, all of which showed the break in the curve at very nearly the same age (Table III).

The results tabulated in Table I11 were obtained with different manometers and in various types of culture-vessels. These experiments were carried out at irregular intervals over a period of several months during which time many different batches of broth were used

In order to make sure that the break in the curve would be as sudden as manometric readings at 10-minute intervals indicated, the readings were made at intervals of 2 minutes. From data presented in Table I1 and plotted on Fig. 2, it may be seen that the transition in rates surprisingly occurred within a 2-minute interval.