碩士 / 國立臺灣大學 / 植物學系 / 81 / Synechococcus RF-1 is an N-fixing unicellular cyanobacterium.
Which is found to have circadian rhythm of N-fixing activity.
Present study is aimed to characterize the utilization of
nitrate and the control step of this process. The kinetics of
the uptake of nitrate and of the enzyme nitrate reductase were
studied. It was revealed that both of the cells grown in the
presence or absence of nitrate did have approximately the same
NR activity， indicating that nitrate is not an obligate
inducer for NR . In the cells grown under L/D cycle，the NR
activity remained nearly unchanged during a cycle. The turnover
rate of NR was very low even when chloramphenicol was added to
the cultures cultivated with nitrate as N-source. This implies
that the NR in Synechoccus RF-1 is rather stable in the cells.
The comparison of the uptake of nitrate in the cells grown in
the light with that grown in the dark shows that there is an
ossillation in the magnitude of nitrate uptake during a L/D
cycle . The cells keep the rhythmic ossillation of nitrate
uptake even when they were transfered to a LL conditions. All
of the results indicate that it is the uptake of nitrate rather
than the assimilation process which regulate the ossillation of
nitrate utilization. Ammonium is an effective inhibitor for
nitrate utilization . It was found that ammonium did not
inhibit NR activity directly . Rather it inhibited the uptake
of nitrate via its product， glutamine ，like some of other
Cyanophyte.
| Identifer | oai:union.ndltd.org:TW/081NTU00366003 |
| Date | January 1993 |
| Creators | Lin,Shu-Shiang, 林淑香 |
| Contributors | Wu,Jiunn-Tzong, 吳俊宗 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 61 |
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