title: Oxygenic and anoxygenic photosynthesis in a microbial mat from an anoxic and sulfidic spring.
abstract: Oxygenic and anoxygenic photosynthesis were studied with microsensors in microbial mats found at 9-10 m depth in anoxic and sulfidic water in Little Salt Spring (Florida, USA). The lake sediments were covered with a 1-2 mm thick red mat dominated by filamentous Cyanobacteria, below which Green Sulfur Bacteria (GSB, Chlorobiaceae) were highly abundant. Within 4 mm inside the mats, the incident radiation was attenuated to undetectable levels. In situ microsensor data showed both oxygenic photosynthesis in the red surface layer and light-induced sulfide dynamics up to 1 cm depth. Anoxygenic photosynthesis occurred during all daylight hours, with complete sulfide depletion around midday. Oxygenic photosynthesis was limited to 4 h per day, due to sulfide inhibition in the early morning and late afternoon. Laboratory measurements on retrieved samples showed that oxygenic photosynthesis was fully but reversibly inhibited by sulfide. In patches Fe(III) alleviated the inhibition of oxygenic photosynthesis by sulfide. GSB were resistant to oxygen and showed a low affinity to sulfide. Their light response showed saturation at very low intensities.
authors.affiliation: Microsensor Group, Max-Planck-Institute for Marine Microbiology, Celsiusstrasse 1, Bremen, 28359, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: de Beer
authors.affiliation: HYDRA Institute for Marine Sciences, Via del Forno 80, 57034 Campo nell'Elba (LI), Italy.
authors.forename: Miriam
authors.initials: M
authors.lastname: Weber
authors.affiliation: Microsensor Group, Max-Planck-Institute for Marine Microbiology, Celsiusstrasse 1, Bremen, 28359, Germany.
authors.forename: Arjun
authors.identifier: 0000-0002-0389-5589
authors.initials: A
authors.lastname: Chennu
authors.affiliation: Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, 45221, USA.
authors.forename: Trinity
authors.initials: T
authors.lastname: Hamilton
authors.affiliation: HYDRA Institute for Marine Sciences, Via del Forno 80, 57034 Campo nell'Elba (LI), Italy.
authors.forename: Christian
authors.initials: C
authors.lastname: Lott
authors.affiliation: Department of Geosciences, Pennsylvania State University, University Park, PA, 16802, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Macalady
authors.affiliation: Microsensor Group, Max-Planck-Institute for Marine Microbiology, Celsiusstrasse 1, Bremen, 28359, Germany.|Geomicrobiology Laboratory, Dept. of Earth & Environmental Sciences, University of Michigan, Ann Arbor, MI, 48109, USA.
authors.forename: Judith
authors.initials: J
authors.lastname: M Klatt
mesh_terms: D019414:Chlorobi / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000458:Cyanobacteria / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D005290:Ferric Compounds / Q000032:analysis / Q000378:metabolism; D005431:Florida; D045482:Hot Springs / Q000032:analysis / Q000382:microbiology*; D060106:Lakes / Q000032:analysis / Q000382:microbiology*; D010100:Oxygen / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology; D013440:Sulfides / Q000032:analysis / Q000378:metabolism*
chemical_list: D005290:Ferric Compounds; D013440:Sulfides; D010100:Oxygen