NUTRITION OF PLATYDORINA CAUDATA KOFOID

The vitamins p-aminobenzoic acid, thiamine, biotin, nicotinamide, and B12 were tested for their ability to stimulate growth. Only vitamin B12 was required. Urea and NaNO2 supported excellent growth, although sodium nitrite, ammonium nitrate, and the Casamino acids supported only fair growth. Platydorina grew aerobically in the absence of an exogenous source of carbon; however a carbon source was required for anaerobic growth. Of 25 carbon compounds examined, isocitrate supported anaerobic growth in the light equalling the aerobic controls. Growth did not occur aerobically or anaerobically in the dark with any carbon source examined. Growth was excellent at pH values in excess of 7.0. Growth at pH 10.0 was 4 times that at 7.0 in strain I.U. 850 and twice that at 7.0 in strain Kan-3E. Growth was accelerated with the increase in temperatures but this increase may well be due to the increased intensity of light to which the cultures were exposed at the higher terperatures.