. Biological structure and function; proceedings. Biochemistry; Cytology. 296 DOUGLAS C. PRATT, ALBERT W. FRENKEL, AND DONALD D. HICKMAN with air enriched with CO.,, and the rate of chlorophyll formation and growth was varied by adjusting the flow of air through the spargers of the culture tubes. With this method, however, it was difficult to obtain reproducible results, except for the conditions when the cultures were gassed rapidly* with air or with nitrogen. To obtain more reproducible results we secured the following gas mixtures: 0-5, 1-55, and 7-3% oxygen in nitrogen supplemented with 1%
. Biological structure and function; proceedings. Biochemistry; Cytology. 296 DOUGLAS C. PRATT, ALBERT W. FRENKEL, AND DONALD D. HICKMAN with air enriched with CO.,, and the rate of chlorophyll formation and growth was varied by adjusting the flow of air through the spargers of the culture tubes. With this method, however, it was difficult to obtain reproducible results, except for the conditions when the cultures were gassed rapidly* with air or with nitrogen. To obtain more reproducible results we secured the following gas mixtures: 0-5, 1-55, and 7-3% oxygen in nitrogen supplemented with 1% CO2 (the values for oxygen indicated here were obtained by mass spectrometric analysis). All cultures were gassed at sufficiently rapid rates* so that a further increase in gassing. Fig. I. Effect of oxygen tension in the gassing mixtures on growth of R. riibriwi in the dark (based on change in packed cell volume per ml. of culture suspension) measured four days after inoculation. Initial concentration o-ii /nl. of packed cells per ml. of culture suspension. Rate of gassing through spargers at 35 ml. of gas mixture per minute per 40 ml. of culture suspension in 100 ml. culture tubes. Culture tubes incubated at 30". rates caused little if any effect on rates of growth and chlorophyll production. Figure i shows the effect of oxygen tension in the gassing mixtures on total growth per culture as measured after four days of incubation in the dark. Growth was measured by measuring changes in cell mass or by measuring changes in turbidity at 680 m/x calibrated against packed cell volumes of aliquots of the culture suspensions which were centrifuged for 35 minutes at 2000 times gravity in Hopkins vaccine tubes. While growth saturates at about 2",, oxygen (Fig. 1), chlorophyll concentration on a cell volume basis decreases with increasing oxygen tensions and reaches * 35 40 ml. of gas per minute per 40 cm^ of liquid Please note that these images are extracted from sc
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