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Blue Light Requirement for HC0 3 Uptake and Its Action Spectrum in Monoraphidium braunii
Author(s) -
Giráldez N.,
Aparicio P. J.,
Quiñones M. A.
Publication year - 1998
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1998.tb09702.x
Subject(s) - periplasmic space , action spectrum , biophysics , assimilation (phonology) , irradiation , photochemistry , chemistry , biology , biochemistry , escherichia coli , linguistics , philosophy , gene , physics , nuclear physics
The uptake and assimilation of HCO 3 by the green unicellular alga Monoraphidium braunii can be monitored by the alkalinization of the external medium or by the O 2 evolution associated with the uptake and reduction of this anion. The activation of HCO 3 uptake in this microalga required the irradiation of the cell suspensions with low photon fluence rates of short wavelength radiation. Thus, when the cells were irradiated with strong red light in the presence of HCO 3 , very little alkalinization of the external medium or O 2 evolution could be observed. The O 2 evolution rates measured under red light could be due to the assimilation of the CO 2 derived from the HCO 3 present in the medium. The blue light‐dependent O 2 evolution rates were not diminished by a periplasmic carbonic anhydrase inhibitor, suggesting that HCO 3 ‐dependent O 2 evolution was due to the photoactivation of a selective HCO 3 uptake system at the plasma membrane. The action spectrum for HCO 3 ‐ uptake in M. braunii was very similar to those reported for NO 3 ‐ and CI ‐ suggested that a flavoprotein may be the photoreceptor for this response.