Photo- and heterotrophic nitrogenase activity by the cyano-bacterium Nostoc in symbiosis with the bryophyte Anthoceros
In symbiosis with Anthoceros, Nostoc is thought to do little or no photosynthesis. However, light-dependent /sup 14/CO/sub 2/ fixation by symbiotic Nostoc, freshly isolated from pure cultures of the reconstituted Anthoceros-Nostoc association, was 16% of that by free-living Nostoc. A DCMU-resistant mutant of Nostoc was isolated that fixed CO/sub 2/ at rates comparable to wild-type in both symbiotic and free-living growth states. To determine if symbiotic Nostoc can use its photosynthate directly to fix nitrogen, acetylene reduction by Anthoceros associations reconstituted with wild-type Nostoc was compared to associations with the DCMU-resistant mutant. In wild-type Anthoceros-Nostoc acetylene reduction was inhibited 97% by 5 ..mu..M DCMU, while inhibition of the DCMU-resistant Nostoc association was only 63%. Additions of glucose, fructose, maltose or sucrose to wild-type associations completely restored DCMU-inhibited acetylene reduction in the light. Acetylene reduction in the dark was stimulated by glucose, attaining 84% of the uninhibited light-dependent value. The authors conclude that symbiotic Nostoc maintains a pool of photosynthate which supports nitrogenase activity. The pool can also be supplemented from plant sources.
- Research Organization:
- Univ. of California, Davis, CA
- OSTI ID:
- 6072906
- Report Number(s):
- CONF-8707108-; TRN: 87-037230
- Journal Information:
- Plant Physiol., Suppl.; (United States), Vol. 83:4; Conference: Annual meeting of the American Society of Plant Physiologists, St. Louis, MO, USA, 19 Jul 1987
- Country of Publication:
- United States
- Language:
- English
Similar Records
Mechanism of nitrogenase switch-off by oxygen. [Klebsiella pneumoniae; Rhodopseudomonas sphaeroides f. sp. denitrificans; Rhodopseudomonas capsulate]
Related Subjects
CHLOROPLASTS
BIOLOGICAL FUNCTIONS
MITOCHONDRIA
ORGANIC SULFUR COMPOUNDS
BIOSYNTHESIS
ANIONS
ATP
CYSTEINE
EUGLENA
LABELLED COMPOUNDS
LIPIDS
MAGNESIUM
PLASMIDS
SULFATES
SULFUR 35
TRACER TECHNIQUES
VISIBLE RADIATION
ALGAE
ALKALINE EARTH METALS
AMINO ACIDS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHARGED PARTICLES
DAYS LIVING RADIOISOTOPES
ELECTROMAGNETIC RADIATION
ELEMENTS
EVEN-ODD NUCLEI
FUNCTIONS
IONS
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MASTIGOPHORA
METALS
MICROORGANISMS
NUCLEI
NUCLEOTIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANOIDS
OXYGEN COMPOUNDS
PLANTS
RADIATIONS
RADIOISOTOPES
SULFUR COMPOUNDS
SULFUR ISOTOPES
SYNTHESIS
THIOLS
UNICELLULAR ALGAE
550201* - Biochemistry- Tracer Techniques