Centre Algatech

Single-cell regulation of N2 fixation and photosynthesis in filamentous cyanobacteria

The interplay between photosynthesis and N2 fixation in filamentous cyanobacteria

We have been studying the interactions between photosynthesis and N2 fixation in cyanobacteria since 2000, when Ilana Berman-Frank visited the laboratory of Ivan Šetlík to perform single-cell measurements of variable fluorescence of the marine diazotrophic cyanobacterium Trichodesmium during the diel cycle. This put her together also with prof. Hendrik Küpper, who was a PhD student of Ivan at that time. Since these pioneering experiments we have enjoyed many years of fruitful collaboration between Třeboň, University of Konstanz and Tel Aviv University. Our research interest is focused mainly on Trichodesmium, but we performed studies also on other diazotrophs such as Anabaena. In our studies, we often use the advantages of the Fluorescence Kinetic Microscope (FKM) that allows us to study photosynthetic activities on the single cell level. Using FKM as well as other photophysiological techniques, we have been able to:

• a) develop hypotheses on the transitional uncoupling of light harvesting phycobiliproteins in Trichodesmium to allow for N2 fixation,
• b) characterize the effects of iron limitation on regulation of photosynthesis in Trichodesmium and
• c) study photoacclimation in Trichodesmium.

In our current project, we explore new single-cell techniques to understand how N2 fixation and photosynthesis are coordinated between individual cells of Trichodesmium to protect nitrogenase enzyme from oxidative damage. Specifically, we aim to characterize the expression, localization and activity of nitrogenase and photosynthetic key complexes at high spatial resolution by combining techniques such as FISH, immunocytochemistry, FKM, confocal microscopy and stable isotope incubations combined with nanoSIMS, in a joint effort with colleagues at Algatech Centre (Dr. Kasia Piwosz, Dr. Grzegorz Konert) as well as collaborators abroad (Dr. Keisuke Inomura (University of Washington, USA), Prof. Yeala Shaked (IUI in Eilat, Israel)).

• Related publications:
• Ferimazová, N, Felcmanová, K, Šetlíková, E, Küpper, H, Maldener, I, Hauska, G, Šedivá, B, Prášil, O. (2013): Regulation of photosynthesis during heterocyst differentiation in Anabaena sp. Strain PCC 7120 investigated in vivo at single-cell level by chlorophyll fluorescence kinetic microscopy. Photosynthesis Research 116: 79-91.
• Andersen, E., Lohscheider, J., Šetlíková, E., Adamska, I., Šimek, M., Küpper, H. (2010): Acclimation of Trichodesmium erythraeum ISM101 to high and low irradiance analysed on the physiological, biophysical and biochemical level. New Phytologist 185: 173-188.
• Küpper, H., Andersen, E., Wiegert, S., Šimek, M., Leitenmaier, B., Šetlík, I. (2009): Reversible coupling of individual phycobiliprotein isoforms during state transitions in the cyanobacterium Trichodesmium analysed by single-cell fluorescence kinetic measurements. Biochimica et Biophysica Acta 1787: 155-167.
• Küpper, H., Šetlík, I., Seifert, S., Prášil, O., Šetlíková, E., Strittmatter, M., Levitan, O., Lohscheider, J., Adamska, I., Berman-Brank, I. (2008): Iron limitation in the marine cyanobacterium Trichodesmium reveals new insights into regulation of photosynthesis and nitrogen fixation. New Phytologist 179: 784-798.
• Küpper, H., Ferimazova, N., Šetlík, I., Berman-Frank, I. (2004): Traffic lights in Trichodesmium. Regulation of photosynthesis for nitrogen fixation studied by chlorophyll fluorescence kinetics microscopy. Plant Physiology 135: 2120-2133.
• Berman-Frank, I., Lundgren, P., Chen, Y-B., Küpper, H., Kolber, Z., Bergman, B., Falkowski, P. (2001): Segregation of nitrogen fixation and oxygen photosynthesis in the marine cyanobacterium Trichodesmium. Science 294: 1534-1537.