Comparison of the Photosynthetic Yield of Cyanobacteria and Green Algae: Different Methods Give Different Answers

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 val...

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Published inPloS one Vol. 10; no. 9; p. e0139061
Main Authors Schuurmans, R Milou, van Alphen, Pascal, Schuurmans, J Merijn, Matthijs, Hans C P, Hellingwerf, Klaas J
Format Journal Article
LanguageEnglish
Published United States Public Library of Science 22.09.2015
Public Library of Science (PLoS)
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Summary: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.
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Conceived and designed the experiments: RMS PvA JMS HCPM KJH. Performed the experiments: RMS JMS. Analyzed the data: RMS PvA. Contributed reagents/materials/analysis tools: RMS PvA JMS HCPM KJH. Wrote the paper: RMS PvA HCPM KJH.
Competing Interests: The authors have the following interests. This project was carried out within the research programme of BioSolar Cells (biosolarcells.nl), co-financed by the Dutch Ministry of Economic Affairs. Klaas J. Hellingwerf is employed by Photanol BV. There are no patents, products in development or marketed products to declare. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0139061