Low-light anoxygenic photosynthesis and Fe-S-biogeochemistry in a microbial mat

Sebastian Haas, Dirk de Beer, Judith M. Klatt, Artur Fink, Rebecca Mc Cauley Rench, Trinity L. Hamilton, Volker Meyer, Brian Kakuk, Jennifer L. Macalady

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

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 ( < 400 nm) was the most abundant part of the spectrum followed by green wavelengths (475-530 nm). We measured a light-dependent carbon uptake rate of 14.5 nmol C cm-2 d-1. A 16S rRNA clone library of the green surface mat layer was dominated (74%) by a cluster ( > 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.

Original languageEnglish (US)
Article number858
JournalFrontiers in Microbiology
Volume9
Issue numberAPR
DOIs
StatePublished - Apr 27 2018

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Photosynthesis
Sulfides
Chlorobi
Sulfates
Light
Carbon
Sulfur
Bahamas
Electric Power Supplies
Water
Ultraviolet Rays
Photons
Islands
Clone Cells
pyrite
ferric oxide

All Science Journal Classification (ASJC) codes

  • Microbiology
  • Microbiology (medical)

Cite this

Haas, Sebastian ; Beer, Dirk de ; Klatt, Judith M. ; Fink, Artur ; Rench, Rebecca Mc Cauley ; Hamilton, Trinity L. ; Meyer, Volker ; Kakuk, Brian ; Macalady, Jennifer L. / Low-light anoxygenic photosynthesis and Fe-S-biogeochemistry in a microbial mat. In: Frontiers in Microbiology. 2018 ; Vol. 9, No. APR.
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title = "Low-light anoxygenic photosynthesis and Fe-S-biogeochemistry in a microbial mat",
abstract = "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 ( < 400 nm) was the most abundant part of the spectrum followed by green wavelengths (475-530 nm). We measured a light-dependent carbon uptake rate of 14.5 nmol C cm-2 d-1. A 16S rRNA clone library of the green surface mat layer was dominated (74{\%}) by a cluster ( > 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.",
author = "Sebastian Haas and Beer, {Dirk de} and Klatt, {Judith M.} and Artur Fink and Rench, {Rebecca Mc Cauley} and Hamilton, {Trinity L.} and Volker Meyer and Brian Kakuk and Macalady, {Jennifer L.}",
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Haas, S, Beer, DD, Klatt, JM, Fink, A, Rench, RMC, Hamilton, TL, Meyer, V, Kakuk, B & Macalady, JL 2018, 'Low-light anoxygenic photosynthesis and Fe-S-biogeochemistry in a microbial mat', Frontiers in Microbiology, vol. 9, no. APR, 858. https://doi.org/10.3389/fmicb.2018.00858

Low-light anoxygenic photosynthesis and Fe-S-biogeochemistry in a microbial mat. / Haas, Sebastian; Beer, Dirk de; Klatt, Judith M.; Fink, Artur; Rench, Rebecca Mc Cauley; Hamilton, Trinity L.; Meyer, Volker; Kakuk, Brian; Macalady, Jennifer L.

In: Frontiers in Microbiology, Vol. 9, No. APR, 858, 27.04.2018.

Research output: Contribution to journalArticle

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T1 - Low-light anoxygenic photosynthesis and Fe-S-biogeochemistry in a microbial mat

AU - Haas, Sebastian

AU - Beer, Dirk de

AU - Klatt, Judith M.

AU - Fink, Artur

AU - Rench, Rebecca Mc Cauley

AU - Hamilton, Trinity L.

AU - Meyer, Volker

AU - Kakuk, Brian

AU - Macalady, Jennifer L.

PY - 2018/4/27

Y1 - 2018/4/27

N2 - 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 ( < 400 nm) was the most abundant part of the spectrum followed by green wavelengths (475-530 nm). We measured a light-dependent carbon uptake rate of 14.5 nmol C cm-2 d-1. A 16S rRNA clone library of the green surface mat layer was dominated (74%) by a cluster ( > 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.

AB - 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 ( < 400 nm) was the most abundant part of the spectrum followed by green wavelengths (475-530 nm). We measured a light-dependent carbon uptake rate of 14.5 nmol C cm-2 d-1. A 16S rRNA clone library of the green surface mat layer was dominated (74%) by a cluster ( > 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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