ISSN:
1432-0614
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Summary Azotobacter culture has been investigated in the physiological state in which it fixed molecular nitrogen. A chemically defined medium was formulated that would support the growth ofAzotobacter vinelandii, but not the growth ofSaccharomyces cerevisiae in pure culture, unless a nitrogen source was added. The yeast culture was allowed to grow in mixed culture with the bacterium. Transient and steady-state populations of each organism in mixed culture at various dilution rates were enumerated with hemocytometer under a microscope. The difference in size of the organisms permitted easy resolution. The essential nutrilite, nitrogen, which is fixed by the bacteria and required by yeast caused the yeast to be dependent on the growth of the bacterium. At low dilution rates the yeast population reflected changes in the numbers ofAzotobacter. The numbers ofAzotobacter were identical in pure culture or in mixed culture; thus the interaction can be termed competitive commensalism. In batch culture, yeast had no effect on the rate of nitrogen fixation byAzotobacter. E. Coli ML-30 had a slight inhibitory effect whileC1. pasteurianum exhibited a stimulating effect. In continuous culture at low dilution rates, yeast was found to increase the rate of nitrogen fixation byAzotobacter vinelandii by 4.5%. Differential equations characterizing commensalism in the chemostat have been proposed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00942208
