The results of a preliminary experiment suggested that a complexed
form of cobalt was more efficacious in promoting growth of a
marine phytoplankton than ionic cobalt. The phytoplankton used in this
experiment was Coccolithus huxleyi, a vitamin B₁₂ producer, and the
cobalt complex was cobalt (II)- ethylenediaminetetracetic acid [Co(II)-
EDTA]. A review of the biochemistry of vitamin B₁₂ indicates that a
B₁₂ producer might prefer, if not require, Co(III) instead of Co(II).
Since some of the Co(II)-EDTA in the preliminary experiment might
have become oxidized to Co(III)-EDTA, the observed stimulation of
growth could have been due to Co(III)-EDTA.
Two experiments were performed to determine if Co(III)-EDTA
is more efficacious in stimulating growth than Co(II)-EDTA. Coccolithus
huxleyi, grown in batch cultures with constant illumination, was
used in both experiments. One experiment had cobalt concentrations
of 10 and 1 μg/l; the other had concentrations of 1 and 0.1 μg/1. In
both experiments there were no observed differences in specific growth
rates between treatments of Co(III) as the EDTA complex with 10⁻⁶ M
additional EDTA and Co(II) with 10⁻⁶ M EDTA. Both of these treatments
resulted in a specific growth rate larger than controls without
added EDTA or cobalt. It is not possible to measure the amount of
Co(II)-EDTA that is oxidized to Co(III)-EDTA at the concentrations
used in these experiments. Consequently these results cannot be used
as a basis for rejecting the hypothesis that Co(III) is the required form
of cobalt. Since Co(III)-EDTA without the additional 10⁻⁶ M EDTA was
apparently able to stimulate growth in relation to the controls, it is
assumed that C. huxleyi is capable of utilizing this form of cobalt. / Graduation date: 1975
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/28408 |
| Date | 07 January 1974 |
| Creators | Longaker, Harold L. |
| Contributors | Holton, Robert |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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