ISSN:
1432-072X
Keywords:
Anacystis nidulans
;
CO2 Fixation
;
Regulation
;
Adenine and Pyridine Nucleotides
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Anacystis nidulans (Synechococcus) had a minimal doubling time of 5 hrs at 30°C at saturating light intensity and carbon dioxide concentration. Half maximal growth rates in saturating CO2 occurred at a light intensity of 0.54 mW per cm2, and there was an apparent threshold intensity of 0.13 mW per cm2 below which no growth occurred. Growth rate in saturating light was dependent on the concentration of CO2+H2CO3 in the medium, rather than on total dissolved CO2; half maximal rates were estimated at 0.1 mM CO2+H2CO3. Under saturating conditions of light and CO2, 14CO2 was fixed primarily into 3-PGA, and subsequently moved into sugar phosphates and amino acids. Incorporation into aspartate was relatively slow. CO2 fixation was strictly light-dependent. The changes in adenylate and pyridine nucleotide pools were followed in light/dark and dark/light transitions. Whereas adenylates relaxed slowly over 15–20 min to the concentrations characteristic of illuminated cells following the abrupt changes induced by darkening, the sharp drop in intracellular NADPH showed little dark recovery although rapid restoration occurred on reillumination. Other pyridine nucleotides showed no changes during these transitions. The nucleotide specificity and K m of partially purified GAP dehydrogenase suggest a role for this enzyme in the regulation of CO2 fixation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00428339
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