The Experts below are selected from a list of 1578 Experts worldwide ranked by ideXlab platform
Judith M Klatt - One of the best experts on this subject based on the ideXlab platform.
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low light Anoxygenic Photosynthesis and fe s biogeochemistry in a microbial mat
Frontiers in Microbiology, 2018Co-Authors: Dirk De Beer, Sebastian Haas, Judith M Klatt, Artur Fink, Rebecca Mccauley Rench, Trinity L Hamilton, Volker Meyer, Brian KakukAbstract:We report extremely low-light-adapted Anoxygenic Photosynthesis in a thick microbial mat in Magical Blue Hole, Abaco Island, The Bahamas. Sulfur cycling was reduced by iron oxides and organic carbon limitation. The mat grows below the halocline/oxycline at 30 m depth on the walls of the flooded sinkhole. In situ irradiance at the mat surface on a sunny December day was between 0.021 and 0.084 µmol photons m-2 s-1, and UV light (97% sequence identity) of clones affiliated with Prosthecochloris, a genus within the green sulfur bacteria (GSB), which are obligate Anoxygenic phototrophs. Typical photopigments of brown-colored GSB, bacteriochlorophyll e and (β-)isorenieratene, were abundant in mat samples and their absorption properties are well-adapted to harvest light in the available green and possibly even UV-A spectra. Sulfide from the water column (3-6 µmol L-1) was the main source of sulfide to the mat as sulfate reduction rates in the mats were very low (undetectable-99.2 nmol cm-3 d-1). The anoxic water column was oligotrophic and low in dissolved organic carbon (175-228 µmol L-1). High concentrations of pyrite (FeS2; 1-47 µmol cm-3) together with low microbial process rates (sulfate reduction, CO2 fixation) indicate that the mats function as net sulfide sinks mainly by abiotic processes. We suggest that abundant Fe(III) (4.3-22.2 µmol cm-3) is the major source of oxidizing power in the mat, and that abiotic Fe-S-reactions play the main role in pyrite formation. Limitation of sulfate reduction by low organic carbon availability along with the presence of abundant sulfide-scavenging iron oxides considerably slowed down sulfur cycling in these mats.
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Data_Sheet_1_Low-Light Anoxygenic Photosynthesis and Fe-S-Biogeochemistry in a Microbial Mat.DOCX
2018Co-Authors: Sebastian Haas, Dirk De Beer, Judith M Klatt, Artur Fink, Rebecca Mccauley Rench, Trinity L Hamilton, Volker Meyer, Brian Kakuk, Jennifer L MacaladyAbstract:We report extremely low-light-adapted Anoxygenic Photosynthesis in a thick microbial mat in Magical Blue Hole, Abaco Island, The Bahamas. Sulfur cycling was reduced by iron oxides and organic carbon limitation. The mat grows below the halocline/oxycline at 30 m depth on the walls of the flooded sinkhole. In situ irradiance at the mat surface on a sunny December day was between 0.021 and 0.084 μmol photons m-2 s-1, and UV light (97% sequence identity) of clones affiliated with Prosthecochloris, a genus within the green sulfur bacteria (GSB), which are obligate Anoxygenic phototrophs. Typical photopigments of brown-colored GSB, bacteriochlorophyll e and (β-)isorenieratene, were abundant in mat samples and their absorption properties are well-adapted to harvest light in the available green and possibly even UV-A spectra. Sulfide from the water column (3–6 μmol L-1) was the main source of sulfide to the mat as sulfate reduction rates in the mats were very low (undetectable-99.2 nmol cm-3 d-1). The anoxic water column was oligotrophic and low in dissolved organic carbon (175–228 μmol L-1). High concentrations of pyrite (FeS2; 1–47 μmol cm-3) together with low microbial process rates (sulfate reduction, CO2 fixation) indicate that the mats function as net sulfide sinks mainly by abiotic processes. We suggest that abundant Fe(III) (4.3–22.2 μmol cm-3) is the major source of oxidizing power in the mat, and that abiotic Fe-S-reactions play the main role in pyrite formation. Limitation of sulfate reduction by low organic carbon availability along with the presence of abundant sulfide-scavenging iron oxides considerably slowed down sulfur cycling in these mats.
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oxygenic and Anoxygenic Photosynthesis in a microbial mat from an anoxic and sulfidic spring
Environmental Microbiology, 2017Co-Authors: Dirk De Beer, Judith M Klatt, Trinity L Hamilton, Miriam Weber, Arjun Chennu, Christian Lott, Jennifer L MacaladyAbstract: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.
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Cyanobacteria in sulfidic spring microbial mats can perform oxygenic and Anoxygenic Photosynthesis simultaneously during an entire diurnal period
Frontiers Media S.A., 2016Co-Authors: Dirk De Beer, Lubos Polerecky, Judith M Klatt, Stefan HäuslerAbstract:We used microsensors to study the regulation of oxygenic and Anoxygenic Photosynthesis by light and sulfide in a cyanobacterium dominating microbial mats from cold sulfidic springs. Both photosynthetic modes were performed simultaneously over all H2S concentrations (1–2200 µM) and irradiances (4–52 µmol photons m-2 s-1) tested. Anoxygenic Photosynthesis increased with H2S concentration while the sum of oxygenic and Anoxygenic photosynthetic rates was constant at each light intensity. Thus, the total photosynthetically driven electron transport rate was solely controlled by the irradiance level. The partitioning between the rates of these two photosynthetic modes was regulated by both light and H2S concentration. The plastoquinone pool (PQ) receives electrons from sulfide:quinone:reductase (SQR) in Anoxygenic Photosynthesis and from photosystem II (PSII) in oxygenic Photosynthesis. It is thus the link in the electron transport chain where both pathways intersect, and the compound that controls their partitioning. We fitted our data with a model of the photosynthetic electron transport that includes the kinetics of plastoquinone reduction and oxidation. The model results confirmed that the observed partitioning between photosynthetic modes can be explained by a simple kinetic control based on the affinity of SQR and PSII towards PQ. The SQR enzyme and PSII have similar affinities towards PQ, which explains the concurrent oxygenic and Anoxygenic Photosynthesis over an astonishingly wide range of H2S concentrations and irradiances. The elegant kinetic control of activity makes the cyanobacterium successful in the fluctuating spring environment. We discuss how these specific regulation mechanisms may have played a role in ancient H2S-rich oceans
Jorg Overmann - One of the best experts on this subject based on the ideXlab platform.
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green sulfur bacteria
eLS, 2001Co-Authors: Jorg OvermannAbstract:Green sulfur bacteria are a phylogenetically isolated group of predominantly aquatic bacteria which occur where light reaches anoxic water layers. The cells grow by Anoxygenic Photosynthesis, using reduced sulfur compounds as electron donor for carbon dioxide assimilation. Keywords: Anoxygenic Photosynthesis; green sulfur bacteria; Chlorobiaceae; sulfur cycle; low-light adaptation
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the sulfur cycle in the chemocline of a meromictic salt lake
Limnology and Oceanography, 1996Co-Authors: Jorg Overmann, Thomas J Beatty, Roy H Krause, Ken J HallAbstract:An extremely dense layer of the purple sulfur bacterium Amoebobacter purpureus in the chemocline of meromictic Mahoney Lake (British Columbia) was investigated over a 2-yr period. Within this layer, sulfide, elemental sulfur, and polysulfides were the main species of reduced sulfur. The oxidative part of the sulfur cycle was dominated by Anoxygenic Photosynthesis of A. purpureus. During summer, when sulfide concentrations in the layer were limiting, intracellular sulfur became the main electron donor for Photosynthesis. 634S determinations revealed that the intracellular sulfur reacts chemically with dissolved sulfide to form polysulfides. Polysulfide concentrations decreased over summer, accompanied by an increase in numbers of sulfur-reducing bacteria. Sulfate reduction was the major pathway of sulfide formation. The annual carbon requirement of sulfate-reducing bacteria in the chemocline (22.5 g C m-2 yr-I) was met by the photosynthetic C fixation of A. purpureus (33.5 g C m-2 yr-l). Carbon demand exceeded the concomitant C fixation temporarily in summer, however. The activities of biomass-degrading enzymes and the formation of volatile fatty acids were sufficient to provide the carbon substrates. Our data indicate that in Mahoney Lake, Anoxygenic Photosynthesis and sulfate reduction are only indirectly coupled via degradation and autolysis of photosynthetically formed biomass.
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an extremely low light adapted phototrophic sulfur bacterium from the black sea
Limnology and Oceanography, 1992Co-Authors: Jorg Overmann, Heribert Cypionka, Norbert PfennigAbstract:Five strains of a brown phototrophic sulfur bacterium (Chlorobium phaeobacteroides) were isolated from the chemocline of the Black Sea (80-m depth). All contain bacteriochlorophyll e as the main photosynthetic pigment. The strains revealed extreme low-light adaptation of growth compared to 12 other green and purple sulfur bacterial strains. At very low light intensities (<4 µEinst m‒2 s‒1), the Black Sea strain MN 1 oxidized sulfide faster than the type strain 2430; the latter reached three times higher oxidation rates at light saturation. Low-light adaptation is achieved by an increase of light-harvesting pigments (175% compared to the type strain) and a very low maintenance energy requirement. The efficiency of energy transfer (59%) within light-harvesting structures (chlorosomes) is comparable in other green sulfur bacteria and, therefore, appears to be limited by the molecular organization of the chlorosomes. From data in the literature, a light transmission of 0.0005% of surface irradiance was calculated for the chemocline of the Black Sea. Extrapolation of our laboratory data revealed that Anoxygenic Photosynthesis could account for 4% of total sulfide oxidation under average light conditions in situ and for 13% at maximal surface irradiance in summer.
Sean A. Crowe - One of the best experts on this subject based on the ideXlab platform.
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Anoxygenic Photosynthesis and the delayed oxygenation of earth s atmosphere
arXiv: Earth and Planetary Astrophysics, 2019Co-Authors: Kazumi Ozaki, Sean A. Crowe, Rachel L. Simister, Katharine J Thompson, Christopher T ReinhardAbstract:The emergence of oxygenic Photosynthesis created a new niche with dramatic potential to transform energy flow through Earth's biosphere. However, more primitive forms of Photosynthesis that fix CO2 into biomass using electrons from reduced species like Fe(II) and H2 instead of water would have competed with Earth's early oxygenic biosphere for essential nutrients. Here, we combine experimental microbiology, genomic analyses, and Earth system modeling to demonstrate that competition for light and nutrients in the surface ocean between oxygenic phototrophs and Fe(II)-oxidizing, Anoxygenic photosynthesizers (photoferrotrophs) translates into diminished global photosynthetic O2 release when the ocean interior is Fe(II)-rich. These results provide a simple ecophysiological mechanism for inhibiting atmospheric oxygenation during Earth's early history. We also find a novel positive feedback within the coupled C-P-O-Fe cycles that can lead to runaway planetary oxygenation as rising atmospheric pO2 sweeps the deep ocean of the ferrous iron substrate for photoferrotrophy.
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Anoxygenic Photosynthesis and the delayed oxygenation of earth s atmosphere
Nature Communications, 2019Co-Authors: Kazumi Ozaki, Sean A. Crowe, Rachel L. Simister, Katharine J Thompson, Christopher T ReinhardAbstract:The emergence of oxygenic Photosynthesis created a new niche with dramatic potential to transform energy flow through Earth’s biosphere. However, more primitive forms of Photosynthesis that fix CO2 into biomass using electrons from reduced species like Fe(II) and H2 instead of water would have competed with Earth’s early oxygenic biosphere for essential nutrients. Here, we combine experimental microbiology, genomic analyses, and Earth system modeling to demonstrate that competition for light and nutrients in the surface ocean between oxygenic phototrophs and Fe(II)-oxidizing, Anoxygenic photosynthesizers (photoferrotrophs) translates into diminished global photosynthetic O2 release when the ocean interior is Fe(II)-rich. These results provide a simple ecophysiological mechanism for inhibiting atmospheric oxygenation during Earth’s early history. We also find a novel positive feedback within the coupled C-P-O-Fe cycles that can lead to runaway planetary oxygenation as rising atmospheric pO2 sweeps the deep ocean of the ferrous iron substrate for photoferrotrophy. Competition dynamics between early Earth photosynthetic microorganisms are unclear. Here, the authors demonstrate that competition for light and nutrients between oxygenic phototrophs and Fe-based photosynthesizers in surface oceans provides a novel ecophysiological mechanism for the protracted oxygenation of Earth’s atmosphere.
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nutrient acquisition and the metabolic potential of photoferrotrophic chlorobi
Frontiers in Microbiology, 2017Co-Authors: Katharine J Thompson, Rachel L. Simister, Aria S. Hahn, Steven J. Hallam, Sean A. CroweAbstract:Anoxygenic Photosynthesis evolved prior to oxygenic Photosynthesis and harnessed energy from sunlight to support biomass production on the early Earth. Models that consider the availability of electron donors predict that Anoxygenic Photosynthesis using Fe(II), known as photoferrotrophy, would have supported most global primary production before the proliferation of oxygenic phototrophs at approximately 2.3 billion years ago. These photoferrotrophs have also been implicated in the deposition of banded iron formations (BIFs), the world’s largest sedimentary iron ore deposits that formed mostly in late Archean and early Proterozoic Eons. In this work we present new data and analyses that illuminate the metabolic capacity of photoferrotrophy in the phylum Chlorobi. Our laboratory growth experiments and biochemical analyses demonstrate that photoferrotrophic Chlorobi are capable of assimilatory sulfate reduction and nitrogen fixation under sulfate and nitrogen limiting conditions, respectively. Furthermore, the evolutionary histories of key enzymes in both sulfur (CysH and CysD) and nitrogen fixation (NifDKH) pathways are convoluted; protein phylogenies, however, suggest that early Chlorobi could have had the capacity to assimilate sulfur and fix nitrogen. We argue, then, that the capacity for photoferrotrophic Chlorobi to acquire these key nutrients enabled them to support primary production and underpin global biogeochemical cycles in the Precambrian.
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chemoautotrophy and Anoxygenic Photosynthesis within the water column of a large meromictic tropical lake lake kivu east africa
Limnology and Oceanography, 2016Co-Authors: Cedric Morana, Sean A. Crowe, Fleur Roland, Marc Lliros, Alberto Borges, Francois Darchambeau, Steven BouillonAbstract:We quantified chemoautotrophic and Anoxygenic photosynthetic microbial production in the water column of Lake Kivu, a permanently stratified tropical lake situated amidst volcanic activity, and aimed to identify the microorganisms involved in these processes through the analysis of their phospholipid fatty acid (PLFA) content and stable isotope ( 13 C) labelling of PLFA in a set of incubation experiments. Data demonstrate the existence of a biogeochemically active chemoautotrophic bacterial community in the redoxcline of Lake Kivu (50‐70 m). PLFA data indicate that the bacterial communities are structured vertically in the water column, with a large dissimilarity between the oxic and anoxic waters. Maximum volumetric dark CO2 fixation rates measured in Lake Kivu were in the same range as values reported from H2S-rich marine redoxclines, such as the Black and Baltic Seas, and the Cariaco Basin. Similarly, maximal chemoautotrophic activities in Lake Kivu were observed in sulfidic waters, just below the oxycline. Anoxygenic photosynthetic production was never observed in the main basin of Lake Kivu. However, Anoxygenic phototrophs largely dominated CO2 fixation in the illuminated redoxcline of Kabuno Bay, a shallower ferruginous sub-basin. Overall, this study supports the idea that chemoautotrophs and/or Anoxygenic photoautotrophs might play an important role in the flow of carbon and energy in permanently stratified tropical ecosystems. In Lake Kivu, these processes significantly contribute to organic matter biosynthesis and exert an indirect control on oxygenic photoautotrophs by shortcircuiting the vertical transport of nutrients to the illuminated and oxygenated surface waters.
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photoferrotrophs thrive in an archean ocean analogue
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Sean A. Crowe, Carriayne Jones, Sergei Katsev, Cedric Magen, Andrew H Oneill, Arne Sturm, Donald E Canfield, Douglas G Haffner, Alfornso Mucci, Bjorn SundbyAbstract:Abstract Considerable discussion surrounds the potential role of Anoxygenic phototrophic Fe(II)-oxidizing bacteria in both the genesis of Banded Iron Formations (BIFs) and early marine productivity. However, Anoxygenic phototrophs have yet to be identified in modern environments with comparable chemistry and physical structure to the ancient Fe(II)-rich (ferruginous) oceans from which BIFs deposited. Lake Matano, Indonesia, the eighth deepest lake in the world, is such an environment. Here, sulfate is scarce ( 100-m-deep chemocline. Within this sulfide-poor, Fe(II)-rich, illuminated chemocline, we find a populous assemblage of Anoxygenic phototrophic green sulfur bacteria (GSB). These GSB represent a large component of the Lake Matano phototrophic community, and bacteriochlorophyll e, a pigment produced by low-light-adapted GSB, is nearly as abundant as chlorophyll a in the lake's euphotic surface waters. The dearth of sulfide in the chemocline requires that the GSB are sustained by phototrophic oxidation of Fe(II), which is in abundant supply. By analogy, we propose that similar microbial communities, including populations of sulfate reducers and photoferrotrophic GSB, likely populated the chemoclines of ancient ferruginous oceans, driving the genesis of BIFs and fueling early marine productivity. Anoxygenic Photosynthesis banded iron formation green sulfur bacteria iron oxidation Lake Matano
Trinity L Hamilton - One of the best experts on this subject based on the ideXlab platform.
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the trouble with oxygen the ecophysiology of extant phototrophs and implications for the evolution of oxygenic Photosynthesis
Free Radical Biology and Medicine, 2019Co-Authors: Trinity L HamiltonAbstract:The ability to harvest light to drive chemical reactions and gain energy provided microbes access to high energy electron donors which fueled primary productivity, biogeochemical cycles, and microbial evolution. Oxygenic Photosynthesis is often cited as the most important microbial innovation-the emergence of oxygen-evolving Photosynthesis, aided by geologic events, is credited with tipping the scale from a reducing early Earth to an oxygenated world that eventually lead to complex life. Anoxygenic Photosynthesis predates oxygen-evolving Photosynthesis and played a key role in developing and fine-tuning the photosystem architecture of modern oxygenic phototrophs. The release of oxygen as a by-product of metabolic activity would have caused oxidative damage to anaerobic microbiota that evolved under the anoxic, reducing conditions of early Earth. Photosynthetic machinery is particularly susceptible to the adverse effects of oxygen and reactive oxygen species and these effects are compounded by light. As a result, phototrophs employ additional detoxification mechanisms to mitigate oxidative stress and have evolved alternative oxygen-dependent enzymes for chlorophyll biosynthesis. Phylogenetic reconstruction studies and biochemical characterization suggest photosynthetic reactions centers, particularly in Cyanobacteria, evolved to both increase efficiency of electron transfer and avoid photodamage caused by chlorophyll radicals that is acute in the presence of oxygen. Here we review the oxygen and reactive oxygen species detoxification mechanisms observed in extant Anoxygenic and oxygenic photosynthetic bacteria as well as the emergence of these mechanisms over evolutionary time. We examine the distribution of phototrophs in modern systems and phylogenetic reconstructions to evaluate the emergence of mechanisms to mediate oxidative damage and highlight changes in photosystems and reaction centers, chlorophyll biosynthesis, and niche space in response to oxygen production. This synthesis supports an emergence of H2S-driven Anoxygenic Photosynthesis in Cyanobacteria prior to the evolution of oxygenic Photosynthesis and underscores a role for the former metabolism in fueling fine-tuning of the oxygen evolving complex and mechanisms to repair oxidative damage. In contrast, we note the lack of elaborate mechanisms to deal with oxygen in non-cyanobacterial Anoxygenic phototrophs suggesting these microbes have occupied similar niche space throughout Earth's history.
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low light Anoxygenic Photosynthesis and fe s biogeochemistry in a microbial mat
Frontiers in Microbiology, 2018Co-Authors: Dirk De Beer, Sebastian Haas, Judith M Klatt, Artur Fink, Rebecca Mccauley Rench, Trinity L Hamilton, Volker Meyer, Brian KakukAbstract:We report extremely low-light-adapted Anoxygenic Photosynthesis in a thick microbial mat in Magical Blue Hole, Abaco Island, The Bahamas. Sulfur cycling was reduced by iron oxides and organic carbon limitation. The mat grows below the halocline/oxycline at 30 m depth on the walls of the flooded sinkhole. In situ irradiance at the mat surface on a sunny December day was between 0.021 and 0.084 µmol photons m-2 s-1, and UV light (97% sequence identity) of clones affiliated with Prosthecochloris, a genus within the green sulfur bacteria (GSB), which are obligate Anoxygenic phototrophs. Typical photopigments of brown-colored GSB, bacteriochlorophyll e and (β-)isorenieratene, were abundant in mat samples and their absorption properties are well-adapted to harvest light in the available green and possibly even UV-A spectra. Sulfide from the water column (3-6 µmol L-1) was the main source of sulfide to the mat as sulfate reduction rates in the mats were very low (undetectable-99.2 nmol cm-3 d-1). The anoxic water column was oligotrophic and low in dissolved organic carbon (175-228 µmol L-1). High concentrations of pyrite (FeS2; 1-47 µmol cm-3) together with low microbial process rates (sulfate reduction, CO2 fixation) indicate that the mats function as net sulfide sinks mainly by abiotic processes. We suggest that abundant Fe(III) (4.3-22.2 µmol cm-3) is the major source of oxidizing power in the mat, and that abiotic Fe-S-reactions play the main role in pyrite formation. Limitation of sulfate reduction by low organic carbon availability along with the presence of abundant sulfide-scavenging iron oxides considerably slowed down sulfur cycling in these mats.
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Data_Sheet_1_Low-Light Anoxygenic Photosynthesis and Fe-S-Biogeochemistry in a Microbial Mat.DOCX
2018Co-Authors: Sebastian Haas, Dirk De Beer, Judith M Klatt, Artur Fink, Rebecca Mccauley Rench, Trinity L Hamilton, Volker Meyer, Brian Kakuk, Jennifer L MacaladyAbstract:We report extremely low-light-adapted Anoxygenic Photosynthesis in a thick microbial mat in Magical Blue Hole, Abaco Island, The Bahamas. Sulfur cycling was reduced by iron oxides and organic carbon limitation. The mat grows below the halocline/oxycline at 30 m depth on the walls of the flooded sinkhole. In situ irradiance at the mat surface on a sunny December day was between 0.021 and 0.084 μmol photons m-2 s-1, and UV light (97% sequence identity) of clones affiliated with Prosthecochloris, a genus within the green sulfur bacteria (GSB), which are obligate Anoxygenic phototrophs. Typical photopigments of brown-colored GSB, bacteriochlorophyll e and (β-)isorenieratene, were abundant in mat samples and their absorption properties are well-adapted to harvest light in the available green and possibly even UV-A spectra. Sulfide from the water column (3–6 μmol L-1) was the main source of sulfide to the mat as sulfate reduction rates in the mats were very low (undetectable-99.2 nmol cm-3 d-1). The anoxic water column was oligotrophic and low in dissolved organic carbon (175–228 μmol L-1). High concentrations of pyrite (FeS2; 1–47 μmol cm-3) together with low microbial process rates (sulfate reduction, CO2 fixation) indicate that the mats function as net sulfide sinks mainly by abiotic processes. We suggest that abundant Fe(III) (4.3–22.2 μmol cm-3) is the major source of oxidizing power in the mat, and that abiotic Fe-S-reactions play the main role in pyrite formation. Limitation of sulfate reduction by low organic carbon availability along with the presence of abundant sulfide-scavenging iron oxides considerably slowed down sulfur cycling in these mats.
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oxygenic and Anoxygenic Photosynthesis in a microbial mat from an anoxic and sulfidic spring
Environmental Microbiology, 2017Co-Authors: Dirk De Beer, Judith M Klatt, Trinity L Hamilton, Miriam Weber, Arjun Chennu, Christian Lott, Jennifer L MacaladyAbstract: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.
Dirk De Beer - One of the best experts on this subject based on the ideXlab platform.
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low light Anoxygenic Photosynthesis and fe s biogeochemistry in a microbial mat
Frontiers in Microbiology, 2018Co-Authors: Dirk De Beer, Sebastian Haas, Judith M Klatt, Artur Fink, Rebecca Mccauley Rench, Trinity L Hamilton, Volker Meyer, Brian KakukAbstract:We report extremely low-light-adapted Anoxygenic Photosynthesis in a thick microbial mat in Magical Blue Hole, Abaco Island, The Bahamas. Sulfur cycling was reduced by iron oxides and organic carbon limitation. The mat grows below the halocline/oxycline at 30 m depth on the walls of the flooded sinkhole. In situ irradiance at the mat surface on a sunny December day was between 0.021 and 0.084 µmol photons m-2 s-1, and UV light (97% sequence identity) of clones affiliated with Prosthecochloris, a genus within the green sulfur bacteria (GSB), which are obligate Anoxygenic phototrophs. Typical photopigments of brown-colored GSB, bacteriochlorophyll e and (β-)isorenieratene, were abundant in mat samples and their absorption properties are well-adapted to harvest light in the available green and possibly even UV-A spectra. Sulfide from the water column (3-6 µmol L-1) was the main source of sulfide to the mat as sulfate reduction rates in the mats were very low (undetectable-99.2 nmol cm-3 d-1). The anoxic water column was oligotrophic and low in dissolved organic carbon (175-228 µmol L-1). High concentrations of pyrite (FeS2; 1-47 µmol cm-3) together with low microbial process rates (sulfate reduction, CO2 fixation) indicate that the mats function as net sulfide sinks mainly by abiotic processes. We suggest that abundant Fe(III) (4.3-22.2 µmol cm-3) is the major source of oxidizing power in the mat, and that abiotic Fe-S-reactions play the main role in pyrite formation. Limitation of sulfate reduction by low organic carbon availability along with the presence of abundant sulfide-scavenging iron oxides considerably slowed down sulfur cycling in these mats.
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Data_Sheet_1_Low-Light Anoxygenic Photosynthesis and Fe-S-Biogeochemistry in a Microbial Mat.DOCX
2018Co-Authors: Sebastian Haas, Dirk De Beer, Judith M Klatt, Artur Fink, Rebecca Mccauley Rench, Trinity L Hamilton, Volker Meyer, Brian Kakuk, Jennifer L MacaladyAbstract:We report extremely low-light-adapted Anoxygenic Photosynthesis in a thick microbial mat in Magical Blue Hole, Abaco Island, The Bahamas. Sulfur cycling was reduced by iron oxides and organic carbon limitation. The mat grows below the halocline/oxycline at 30 m depth on the walls of the flooded sinkhole. In situ irradiance at the mat surface on a sunny December day was between 0.021 and 0.084 μmol photons m-2 s-1, and UV light (97% sequence identity) of clones affiliated with Prosthecochloris, a genus within the green sulfur bacteria (GSB), which are obligate Anoxygenic phototrophs. Typical photopigments of brown-colored GSB, bacteriochlorophyll e and (β-)isorenieratene, were abundant in mat samples and their absorption properties are well-adapted to harvest light in the available green and possibly even UV-A spectra. Sulfide from the water column (3–6 μmol L-1) was the main source of sulfide to the mat as sulfate reduction rates in the mats were very low (undetectable-99.2 nmol cm-3 d-1). The anoxic water column was oligotrophic and low in dissolved organic carbon (175–228 μmol L-1). High concentrations of pyrite (FeS2; 1–47 μmol cm-3) together with low microbial process rates (sulfate reduction, CO2 fixation) indicate that the mats function as net sulfide sinks mainly by abiotic processes. We suggest that abundant Fe(III) (4.3–22.2 μmol cm-3) is the major source of oxidizing power in the mat, and that abiotic Fe-S-reactions play the main role in pyrite formation. Limitation of sulfate reduction by low organic carbon availability along with the presence of abundant sulfide-scavenging iron oxides considerably slowed down sulfur cycling in these mats.
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oxygenic and Anoxygenic Photosynthesis in a microbial mat from an anoxic and sulfidic spring
Environmental Microbiology, 2017Co-Authors: Dirk De Beer, Judith M Klatt, Trinity L Hamilton, Miriam Weber, Arjun Chennu, Christian Lott, Jennifer L MacaladyAbstract: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.
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Cyanobacteria in sulfidic spring microbial mats can perform oxygenic and Anoxygenic Photosynthesis simultaneously during an entire diurnal period
Frontiers Media S.A., 2016Co-Authors: Dirk De Beer, Lubos Polerecky, Judith M Klatt, Stefan HäuslerAbstract:We used microsensors to study the regulation of oxygenic and Anoxygenic Photosynthesis by light and sulfide in a cyanobacterium dominating microbial mats from cold sulfidic springs. Both photosynthetic modes were performed simultaneously over all H2S concentrations (1–2200 µM) and irradiances (4–52 µmol photons m-2 s-1) tested. Anoxygenic Photosynthesis increased with H2S concentration while the sum of oxygenic and Anoxygenic photosynthetic rates was constant at each light intensity. Thus, the total photosynthetically driven electron transport rate was solely controlled by the irradiance level. The partitioning between the rates of these two photosynthetic modes was regulated by both light and H2S concentration. The plastoquinone pool (PQ) receives electrons from sulfide:quinone:reductase (SQR) in Anoxygenic Photosynthesis and from photosystem II (PSII) in oxygenic Photosynthesis. It is thus the link in the electron transport chain where both pathways intersect, and the compound that controls their partitioning. We fitted our data with a model of the photosynthetic electron transport that includes the kinetics of plastoquinone reduction and oxidation. The model results confirmed that the observed partitioning between photosynthetic modes can be explained by a simple kinetic control based on the affinity of SQR and PSII towards PQ. The SQR enzyme and PSII have similar affinities towards PQ, which explains the concurrent oxygenic and Anoxygenic Photosynthesis over an astonishingly wide range of H2S concentrations and irradiances. The elegant kinetic control of activity makes the cyanobacterium successful in the fluctuating spring environment. We discuss how these specific regulation mechanisms may have played a role in ancient H2S-rich oceans