A METHODFORMAINTAININGA CONTINUOUSUPPLY OF MARINEDIATOMSBY CULTURE'

• Main Authors: Bostwick H. Ketchum, Alfred, C. Redfield
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Antarctic; The Antarctic; Antarc*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.521.4786; http://www.biolbull.org/content/75/1/165.full.pdf

Culture techniques by means of which large supplies of unicellular organisms can be continually available are greatly in demand. This is especially true of unicellular plants, since they are convenient organ isms for the study of photosynthetic and other metabolic processes. The problem is essentially one of the maintenance of a growing population. So long as no factors develop which limit the rate of multiplication, increase in a culture or population is directly propor tional to the number of organisms present. The growth of the popula tion is logarithmic during the initial period. Some factor or factors in the environment, however, sooner or later lower the division rate. These factors may be limiting nutrient concentrations, formation of inhibitory excretory products, production of non-viable cells in the process of division, or, in the case of photosynthetic plants, limiting light intensity. It was pointed out by Hjort, Jahn and Ottestad (1933), in a study of whaling in the antarctic, that the most advantageous way to exploit a population is to keep it at the level at which the greatest number of new organisms are produced in unit time. This paper presents an application of this principle to a culture method. After procuring the cell concentration at which the greatest daily yield is obtained the culture is maintained at this concentration. A volume of culture con taining the quantity of cells equivalent to the daily increase is with drawn each day and is replaced by an equal volume of fresh sea water enriched with nutrients. We have used the marine diatom, Nitzschia closterium, which is an ideal organism for a study of culture technique. It is a small cell which is readily maintained in pure bacteria-free cultures, and which remains freely suspended in the sea water medium. The culture medium used was that devised by Miquel for freshwater diatoms, and modified by Allen and Nelson (1910) for marine forms. We further modified it by the addition of MgSO4 to the enrichment solutions.