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Nitrogen Fixation Kristen Sanchez Bot 437 – Phycology Spring 2009.

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Presentation on theme: "Nitrogen Fixation Kristen Sanchez Bot 437 – Phycology Spring 2009."— Presentation transcript:

1 Nitrogen Fixation Kristen Sanchez Bot 437 – Phycology Spring 2009

2 Nitrogen Fixation: Taken from Taken from

3 Cyanobacterial heterocyte: Specialized cells in cyanobacteria that function in nitrogen fixation Specialized cells in cyanobacteria that function in nitrogen fixation Regulated by environmental levels of ammonium (NH 4 + ) or nitrate (NO 3 - ) Regulated by environmental levels of ammonium (NH 4 + ) or nitrate (NO 3 - ) Thickened cell walls of heterocytes reduce diffusion of O 2 into the cell Thickened cell walls of heterocytes reduce diffusion of O 2 into the cell

4 Cardona et al, 2009: Study subject: heterocysts of Nostoc punctiformes Study subject: heterocysts of Nostoc punctiformes Goal of the study: analysis of heterocyst membranes and pigment absorption Goal of the study: analysis of heterocyst membranes and pigment absorption Results: Results: Membrane proteome dominated by Photosystem I and ATP-synthase complexesMembrane proteome dominated by Photosystem I and ATP-synthase complexes Monomeric Photosystem II complexes were found in the heterocyst thylakoid membranes!Monomeric Photosystem II complexes were found in the heterocyst thylakoid membranes! Phycobilisomes are present in heterocysts, however, emission intensity is much lower than in vegetative cellsPhycobilisomes are present in heterocysts, however, emission intensity is much lower than in vegetative cells

5 Cardona et al, 2009: Fluoresence emission spectra from vegetative cells/intact filaments (-) and heterocysts (- -) after excitation at 570 nm (A) and 427 nm (B) Fluoresence emission spectra from vegetative cells/intact filaments (-) and heterocysts (- -) after excitation at 570 nm (A) and 427 nm (B) Insert in B is a 5x enlargement, enhancing the peaks originating from PS II Insert in B is a 5x enlargement, enhancing the peaks originating from PS II

6 Cardona et al, 2009: Fluorescence excitation spectra from vegetative cells (-) and heterocysts (- -) Fluorescence excitation spectra from vegetative cells (-) and heterocysts (- -)

7 Cardona et al, 2009: Conclusions: Conclusions: PSII complexes are not degradation productsPSII complexes are not degradation products Phycobilisomes contribute in energy transfer to PS I, though to a lesser degree than in vegetative cellsPhycobilisomes contribute in energy transfer to PS I, though to a lesser degree than in vegetative cells

8 Carpenter and Price, 1976: Study site: eastern Carribean Study site: eastern Carribean Goal of the study: to find an explanation for why Oscillatoria (Trichodesmium) spp. can fix nitrogen in an aerobic environment without heterocysts Goal of the study: to find an explanation for why Oscillatoria (Trichodesmium) spp. can fix nitrogen in an aerobic environment without heterocysts Results: Results: Oscillatoria spp. form colonies differentiated cells in the middle of the colony have reduced pigmentation, do not photosynthesize, do not incorporate CO 2, do not produce O 2 Nitrogenase is deactivated in the presence of O 2 Conclusion: Nitrogen fixation by Oscillatoria spp. is most efficient in calm seas characterized by low wind speeds and light sky cover Conclusion: Nitrogen fixation by Oscillatoria spp. is most efficient in calm seas characterized by low wind speeds and light sky cover

9 The Nitrogen Cycle: Taken from Taken from

10 Fulweiler et al, 2007: Study site: Narragansett Bay, USA; summer 2006 Study site: Narragansett Bay, USA; summer 2006 Hypothesis: A decrease in organic matter deposition to the benthos, and an observed reversal of the net sediment N 2 flux, was caused by a decrease in primary production Hypothesis: A decrease in organic matter deposition to the benthos, and an observed reversal of the net sediment N 2 flux, was caused by a decrease in primary production Results: Sediment core data show that the sediments have switched from being a nitrogen sink to a nitrogen source Results: Sediment core data show that the sediments have switched from being a nitrogen sink to a nitrogen source Conclusion: Some estuaries are feeding nitrogen into the water column that can then be exported to the continental shelf and out to the open ocean Conclusion: Some estuaries are feeding nitrogen into the water column that can then be exported to the continental shelf and out to the open ocean

11 References: Cardona, T., N. Battchikova, P. Zhang, K. Stensjö, E.-M. Aro, P. Lindblad, and A. Magnuson Electron transfer protein complexes in the thylakoid membranes of heterocysts from the cyanobacterium Nostoc punctiforme. Biochimica et Biophysica Acta. Vol 1787: Cardona, T., N. Battchikova, P. Zhang, K. Stensjö, E.-M. Aro, P. Lindblad, and A. Magnuson Electron transfer protein complexes in the thylakoid membranes of heterocysts from the cyanobacterium Nostoc punctiforme. Biochimica et Biophysica Acta. Vol 1787: Carpenter, E.J., and C.C. Price IV Marine Oscillatoria (Trichodesmium): Explanation for Aerobic Nitrogen Fixation Without Heterocysts. Science. Vol 191: Carpenter, E.J., and C.C. Price IV Marine Oscillatoria (Trichodesmium): Explanation for Aerobic Nitrogen Fixation Without Heterocysts. Science. Vol 191: Fulweiler, R.W., S.W. Nixon, B.A. Buckley, and S.L. Granger Reversal of the net dinitrogen gas flux in coastal marine sediments. Nature. Vol 448: Fulweiler, R.W., S.W. Nixon, B.A. Buckley, and S.L. Granger Reversal of the net dinitrogen gas flux in coastal marine sediments. Nature. Vol 448: Graham, L.E., J.M. Graham, and L.W. Wilcox Algae, 2 nd Edition. Pearson Benjamin Cummings. Graham, L.E., J.M. Graham, and L.W. Wilcox Algae, 2 nd Edition. Pearson Benjamin Cummings. Lalli, Carol M., and T.R. Parsons Biological Oceanography an Introduction: 2 nd Edition. Butterworth Heinemann. Lalli, Carol M., and T.R. Parsons Biological Oceanography an Introduction: 2 nd Edition. Butterworth Heinemann.


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