Carbon Dioxide as a Factor Affecting Lag in Bacterial Growth

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Abstract
The necessity for accumulation in the medium or in the cells of a concentration of CO2 essential to culture growth is suggested as a possible cause of the well-known lag period in bacteria. Evidence pointing to this hypothesis was derived from exps. conducted with Escherichia coli cultivated in a simple synthetic medium (Dolloff''s) of low nutrient value. Portions cultured in cotton plugged test-tubes or in vessels through which air containing atmospheric CO2 was continuously bubbled exhibited good growth after a few hrs.; portions continuously aerated with air from which COa had been previously removed by a KOH wash-bottle manifested no growth in a day or more. When portions of the inoculated medium were first for 1 day inhibited from growth by passage of a (CO2-free aeration current, and aeration was then stopped or was continued with CO2 thereafter present in the air current, normal growth soon followed. In these various set-ups, numerous factors proposed by earlier workers as possible causes of lag were so controlled that CO2 removal appeared to be the true variable studied.