title: Hydrogen sulfide can inhibit and enhance oxygenic photosynthesis in a cyanobacterium from sulfidic springs.
abstract: We used microsensors to investigate the combinatory effect of hydrogen sulfide (H2 S) and light on oxygenic photosynthesis in biofilms formed by a cyanobacterium from sulfidic springs. We found that photosynthesis was both positively and negatively affected by H2 S: (i) H2 S accelerated the recovery of photosynthesis after prolonged exposure to darkness and anoxia. We suggest that this is possibly due to regulatory effects of H2 S on photosystem I components and/or on the Calvin cycle. (ii) H2 S concentrations of up to 210 μM temporarily enhanced the photosynthetic rates at low irradiance. Modelling showed that this enhancement is plausibly based on changes in the light-harvesting efficiency. (iii) Above a certain light-dependent concentration threshold H2 S also acted as an inhibitor. Intriguingly, this inhibition was not instant but occurred only after a specific time interval that decreased with increasing light intensity. That photosynthesis is most sensitive to inhibition at high light intensities suggests that H2 S inactivates an intermediate of the oxygen evolving complex that accumulates with increasing light intensity. We discuss the implications of these three effects of H2 S in the context of cyanobacterial photosynthesis under conditions with diurnally fluctuating light and H2 S concentrations, such as those occurring in microbial mats and biofilms.
authors: Max-Planck-Institute for Marine Microbiology, Celsiusstrasse 1, Bremen, 28359, Germany.
authors: Judith M
authors: JM
authors: Klatt
authors: Max-Planck-Institute for Marine Microbiology, Celsiusstrasse 1, Bremen, 28359, Germany.
authors: Sebastian
authors: S
authors: Haas
authors: Max-Planck-Institute for Marine Microbiology, Celsiusstrasse 1, Bremen, 28359, Germany.
authors: Pelin
authors: P
authors: Yilmaz
authors: Max-Planck-Institute for Marine Microbiology, Celsiusstrasse 1, Bremen, 28359, Germany.
authors: Dirk
authors: D
authors: de Beer
authors: Max-Planck-Institute for Marine Microbiology, Celsiusstrasse 1, Bremen, 28359, Germany.|Department of Earth Sciences - Geochemistry, Faculty of Geosciences, Utrecht University, Budapestlaan 4, Utrecht, 3584 CD, The Netherlands.
authors: Lubos
authors: L
authors: Polerecky
mesh_terms: D018441:Biofilms; D000458:Cyanobacteria / Q000378:metabolism* / Q000502:physiology; D003624:Darkness; D006862:Hydrogen Sulfide / Q000737:chemistry*; D060985:Natural Springs / Q000382:microbiology*; D010100:Oxygen / Q000737:chemistry; D010101:Oxygen Consumption / Q000502:physiology*; D010788:Photosynthesis / Q000502:physiology*; D045331:Photosystem I Protein Complex / Q000378:metabolism
chemical_list: D045331:Photosystem I Protein Complex; D010100:Oxygen; D006862:Hydrogen Sulfide