STUDIES ON CHLORELLA VULGARIS II. FURTHER EVIDENCE THAT CHLORELLA CELLS FORM A GROWTH-INHIBITING SUBSTANCE

摘要: PREVIOUS STUDY of the growth unicellular green alga Chlorella vulgaris showed that under conditions employed maximum density population attained in different cultures is independent size inoculum, rate multiplication throughout period varies inversely with initial population, and multiplication, as measured by increase number cells per hour cell a given culture, decreases during nearly entire (Pratt, 1940). It was pointed out data could be interpreted affording evidence presence growth-inhibiting substance produced cells. If such an agent liberated into culture medium result metabolic activities cells, it should possible to measure its effects studying prepared media which some has already occurred. Further experiments bearing on this subject are presented herewith. MATERIALS AND METHODS.-General.-The experimental technique essentially same previously except present work counts were made less frequently than earlier obtained averaging haemacytometer two samples withdrawn from single instead four taken triplicate cultures. The values approximated reasonably closely those for comparable detailed work. Unless otherwise stated, all four-day-old, rapidly growing stock suspensions washed three changes distilled water repeated centrifugation decantation. Preparation nutrient media.-A described 1940) 100 cells/cu. mm. permitted grow lengths time. solution contained KNO3, 0.025 M.; MgSO4 7H21, 0.02 KH2PO4, 0.018 iLI.; FeSO4 7H20, 0.00001 potassium citrate Zn, 0.1 ppm.; Mn, B, 0.05 Cu, 0.001 ppm. A gas mixture containing 5 cent CO2 95 air bubbled continuously through solutions, illuminated Mazda lamps yielding about 20,000 lux at level flasks. temperature flasks 200C.?20. At suitable intervals several centrifuged supernatant drawn 1 Received publication March 20, 1940. sintered Jena glass filters, G 4. filtrate then used, either diluted or undiluted according experiment, prepare new solutions. Since not feasible analyze solutions ascertain precise amount each salt had been removed period, uniform quantities salts added pH adjusted addition H2SO4 4.45, similar watpr.2 total concentrations unifor jm therefore. minimum concentration 0.063 M. (media water). have exceeded 0.12 90 10 water), may considerably below value. In no instance there any over weeks uninoculated so prepared. concluded, therefore, treatment effectively EXPERIMENTS RESULTS.-Influence Chlorella.-Since identical, seemed desirable influence growth. Figure shows results investigation. evident variations significant reported below, since molar exerted relatively little between 0.01 inset final mole liter 97 cent, respectively, standard control liter. micrometabolic elements furnished proportions solution. Only varied. preliminary found fair occurred twice original volume water. This seems afford ample depletion nutrients primary factor determining gradually decreasing slopes curves cultured employed. However, doubled without seriously impairing growth, filtered fortified addi2 As proceeds work, value rises 4.45 approximately 6.5-7.0.