Influence of the Size of the Inoculum on the Growth of Chlorella vulgaris in Freshly Prepared Culture Medium

Abstract

THE IMPORTANCE of the unicellular green alga, Chlorella vulgaris, to plant physiologists engaged in studies of cellular metabolism and especially of photosynthesis is well known. Relatively few detailed studies have been made of its growth, however. The present paper deals with the growth curve of Chlorella in cultures inoculated with different numbers of cells taken from parent cultures of the same age. Multiplication, or increase in cell number, was used as an index of growth in this work, although it is realized that a period of cell enlargement precedes each division, and that growth is the result of these two processes.MATERIALS AND METHoDs.-Cells for the experiments were withdrawn from four-day-old, rapidly growing stock suspensions of Chlorella vulgaris cultured as previously described (Craig and Trelease, 1937; Pratt and Trelease, 1935) in a solution that contained KN0 3 , 0.025M; MgS0 4 "7H 20, 0.02M; KH 2P04, O.OISM; FeS04"7H20, O.OOOOIM; potassium citrate, O.OOOOIM; and Zn, Cu, B, and Mn in approximately the concentrations employed by Trelease and Trelease (1935). The initial pH of this solution was 4.45. New stock cultures were started daily so that there was always available a supply of cells of approximately the same physiological age and activity.Cells were separated from the culture medium and were washed in three changes of distilled water by repeated centrifugation and decantation. They were then suspended in distilled water and the density of the population in the suspension was estimated from haemacytometer counts. Inocula containing the desired number of cells were pipetted into 500 ml. Pyrex glass Florence flasks, each of which contained 150 ml, of the standard nutrient solution. The flasks were continuously illuminated from below by a water-cooled battery of twentyfour 50-watt frosted Mazda lamps. The light intensity, measured by means of a Weston photoelectric-celllight meter, Model 603, varied from 21,000 lux to IS,OOO lux. The lamps were replaced by a complete new set when the intensity fell below this value. The temperature at the level of the flasks varied from ISo to 22°C.A gas mixture containing 5 per cent CO 2 and 95 per cent air was bubbled continuously through the solutions. The cultures were shaken vigorously twice daily to insure separation and uniform suspension of the cells.Growth measurements were made periodically by withdrawing small samples from each flask and estimating the cell population from haemacytometer counts. Triplicates of each culture were prepared, 1 Received for publication November 97, 1939. The author is indebted to Miss Jane Fong for valuable assistance in the laboratory. 52and cell counts were based on the averages of haemacytometer counts of four different samples from each flask. Each point in the figures represents, therefore, the average of twelve samples. The maximum deviation from the mean value occurred in the lower portions of the growth curves and never exceeded 5 per cent. Over the major portion of the curves in all cultures the deviation of ind...

Population Dynamics in Daphnia obtusa Kurz

“…This term is usually used to indicate a direct effect of crowding on the animals. Such direct density effects have been found in many micro-organisms, for example, the effect of concentration of alcohol on the reproductive rate of yeast populations (Klem 1933) or the secretion of "autoinhibitory substances" by populations of Chlorella vulgaris (Pratt 1940 and. In higher animals the fighting that occurs in crowded rodent populations (Errington 1946;Calhoun 1952) or the competition between crowded bands of monkeys (Carpenter 1942) are examples of direct density effects.…”

Nutrition of Cosmarium turpinii

“…The saving effect of urea does not appear to be involved in metal complexing phenomena nor does urea serve as a nitrogen source. Perhaps urea is antagonizing an autotoxin (Pratt 1940). Such a view is supported by the finding that fatty acids have a slight autotoxic effect for Chlorella vulgaris (Spoehr et al 1949).…”

On the stability and Hopf-bifurcation of a multi-delayed competitive population system affected by toxic substances with imprecise biological parameters

“…Researchers, in course of their study over the effect and nature of the toxic elements come to an important observation that the enhanced population of one species might affect or control the growth of another or several other species through the production of allelopathic toxins or stimulants, thus influencing seasonal succession (Rice 1984). Unicellular green alga, chlorella Vulgaris can control the growth of their population and inhibit the growth of planktonic algae Asterionella formosa and Nitzschia frustrum (Bacillareae) with the toxin produced by themselves (Pratt 1940;Pratt and Fong 1940;Rice 1954). Toxic inhibition of phytoplankton by other phytoplankton has been observed by several researchers.…”