Abstract
The continuation of studies already reported 1 has brought out two facts bearing on the question of bacterial lag. First, it has been found that from the moment of seeding and throughout the early hours of growth, the oxygen-uptake of cultures of Bacterium coli increases logarithmically, irrespective of the age of the organisms used for inoculation. Secondly, it was possible to show that the oxygen-consumption calculated per unit of bacterial nitrogen is constant during all phases of growth, when measured under uniform conditions. 2 From these observations, it was inferred that a plausible explanation of the phenomenon of lag was to be found in the changes in average size of cells during the early development of the culture. The experiment to be reported here served, therefore, both to confirm the manometric findings, and to provide direct evidence of the nature of the lag phase.
The data required were obtained by simultaneous determinations of bacterial numbers by plating, and of total bacterial nitrogen by micro-Kjeldahl analysis of the centrifugate, 3 at intervals throughout the growth-period. Beef-extract broth in 200 ml. amounts, containing M/100 phosphate buffer of pH 7.4, was seeded at 37°C. with aliquots of a 24-hour culture of Bact. Coli grown in the same medium. The number of cells and the bacterial nitrogen represented by the inoculum were obtained by analysis of additional aliquots of the parent culture.
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