Cell Size, Macromolecular Composition, and O2 Consumption During Agitated Cultivation of Naegleria gruberi*

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Abstract
Cell size, macromolecular composition, carbohydrate utilization patterns and O2 concentrations were measured throughout the growth stages of N. gruberi in agitated cultures in a complex medium. Biphasic logarithmic growth occurred during the initial 83 h of growth and the mean generation time was 7.0 h and 29 h during initial and secondary log growth stages, respectively. The maximum yield was 5 .times. 106 amoebae/ml. The pH rose rapidly (1 pH unit) during the secondary log growth phase (52-83 h) and continued into the stationary growth phase (83-120 h). Dry weight, total protein, carbohydrate, and RNA per amoeba increased just before the secondary log growth phase. RNA increased 31-35%/amoeba at the end of each phase of log growth. DNA increased .apprx. 2-fold throughout the different growth phases. Average cell size increased 90% during biphasic log growth then decreased during stationary phase. O2 tension decreased from 100 to 18% of saturation during the biphasic growth phase, then increased during stationary growth to .apprx. 100% saturation. Glucose and total carbohydrate assays showed little utilization of those substrates throughout the growth stages. N. gruberi presumably has a predominantly aerobic metabolism, and its metabolism may change during the different growth phases.