title: Comparison of the Photosynthetic Yield of Cyanobacteria and Green Algae: Different Methods Give Different Answers.
abstract: The societal importance of renewable carbon-based commodities and energy carriers has elicited a particular interest for high performance phototrophic microorganisms. Selection of optimal strains is often based on direct comparison under laboratory conditions of maximal growth rate or additional valued features such as lipid content. Instead of reporting growth rate in culture, estimation of photosynthetic efficiency (quantum yield of PSII) by pulse-amplitude modulated (PAM) fluorimetry is an often applied alternative method. Here we compared the quantum yield of PSII and the photonic yield on biomass for the green alga Chlorella sorokiniana 211-8K and the cyanobacterium Synechocystis sp. PCC 6803. Our data demonstrate that the PAM technique inherently underestimates the photosynthetic efficiency of cyanobacteria by rendering a high F0 and a low FM, specifically after the commonly practiced dark pre-incubation before a yield measurement. Yet when comparing the calculated biomass yield on light in continuous culture experiments, we obtained nearly equal values for both species. Using mutants of Synechocystis sp. PCC 6803, we analyzed the factors that compromise its PAM-based quantum yield measurements. We will discuss the role of dark respiratory activity, fluorescence emission from the phycobilisomes, and the Mehler-like reaction. Based on the above observations we recommend that PAM measurements in cyanobacteria are interpreted only qualitatively.
authors.affiliation: Molecular Microbial Physiology Group, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: R Milou
authors.initials: RM
authors.lastname: Schuurmans
authors.affiliation: Molecular Microbial Physiology Group, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Pascal
authors.initials: P
authors.lastname: van Alphen
authors.affiliation: Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: J Merijn
authors.initials: JM
authors.lastname: Schuurmans
authors.affiliation: Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Hans C P
authors.initials: HC
authors.lastname: Matthijs
authors.affiliation: Molecular Microbial Physiology Group, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands; Photanol BV, Amsterdam, The Netherlands.
authors.forename: Klaas J
authors.initials: KJ
authors.lastname: Hellingwerf
mesh_terms: D018533:Biomass; D002708:Chlorella / Q000502:physiology* / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D004579:Electron Transport / Q000528:radiation effects; D005453:Fluorescence; D005470:Fluorometry / Q000379:methods*; D008027:Light; D013058:Mass Spectrometry; D010084:Oxidation-Reduction / Q000528:radiation effects; D010101:Oxygen Consumption / Q000528:radiation effects; D017785:Photons; D010788:Photosynthesis; D052817:Phototrophic Processes / Q000528:radiation effects; D045524:Phycobilisomes / Q000378:metabolism; D046939:Synechocystis / Q000502:physiology* / Q000528:radiation effects
chemical_list: D045524:Phycobilisomes; D002734:Chlorophyll; D000077194:Chlorophyll A