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Microsensor measurements of hydrogen gas dynamics in cyanobacterial microbial mats.

Nielsen M, Revsbech NP, Kühl M - Front Microbiol (2015)

Bottom Line: Depletion could be prevented by addition of molybdate pointing to sulfate reduction as a major sink for H2.As soon as O2 from photosynthesis started to accumulate, the H2 was consumed rapidly and production ceased.Our data give detailed insights into the microscale distribution and dynamics of H2 in cyanobacterial biofilms and mats, and further support that cyanobacterial H2 production can play a significant role in fueling anaerobic processes like e.g., sulfate reduction or anoxygenic photosynthesis in microbial mats.

View Article: PubMed Central - PubMed

Affiliation: Section of Microbiology, Department of Bioscience, Aarhus University Aarhus, Denmark.

ABSTRACT
We used a novel amperometric microsensor for measuring hydrogen gas production and consumption at high spatio-temporal resolution in cyanobacterial biofilms and mats dominated by non-heterocystous filamentous cyanobacteria (Microcoleus chtonoplastes and Oscillatoria sp.). The new microsensor is based on the use of an organic electrolyte and a stable internal reference system and can be equipped with a chemical sulfide trap in the measuring tip; it exhibits very stable and sulfide-insensitive measuring signals and a high sensitivity (1.5-5 pA per μmol L(-1) H2). Hydrogen gas measurements were done in combination with microsensor measurements of scalar irradiance, O2, pH, and H2S and showed a pronounced H2 accumulation (of up to 8-10% H2 saturation) within the upper mm of cyanobacterial mats after onset of darkness and O2 depletion. The peak concentration of H2 increased with the irradiance level prior to darkening. After an initial build-up over the first 1-2 h in darkness, H2 was depleted over several hours due to efflux to the overlaying water, and due to biogeochemical processes in the uppermost oxic layers and the anoxic layers of the mats. Depletion could be prevented by addition of molybdate pointing to sulfate reduction as a major sink for H2. Immediately after onset of illumination, a short burst of presumably photo-produced H2 due to direct biophotolysis was observed in the illuminated but anoxic mat layers. As soon as O2 from photosynthesis started to accumulate, the H2 was consumed rapidly and production ceased. Our data give detailed insights into the microscale distribution and dynamics of H2 in cyanobacterial biofilms and mats, and further support that cyanobacterial H2 production can play a significant role in fueling anaerobic processes like e.g., sulfate reduction or anoxygenic photosynthesis in microbial mats.

No MeSH data available.


Related in: MedlinePlus

Light and chemical gradients in a coastal cyanobacterial mat under an incident photon irradiance of 500 μmol photons m-2 s-1. (A) Depth profiles of photon scalar irradiance, O2 and H2S concentrations. (B) Depth profiles of pH and H2 concentration. Symbols with error bars for chemical parameters represent the mean ± SD (n = 3).
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Figure 4: Light and chemical gradients in a coastal cyanobacterial mat under an incident photon irradiance of 500 μmol photons m-2 s-1. (A) Depth profiles of photon scalar irradiance, O2 and H2S concentrations. (B) Depth profiles of pH and H2 concentration. Symbols with error bars for chemical parameters represent the mean ± SD (n = 3).

Mentions: More detailed microenvironmental analyses of H2 dynamics were done in a sulfidic coastal cyanobacterial mat (Supplementary Figure S1A), whereas measurements in coastal sediment with a surface biofilm of diatoms (Supplementary Figure S1B) showed no accumulation of H2 (data not shown). Spectral scalar irradiance measurements showed strong light attenuation with depth in the dense 1–2 mm thick top layer of the coastal mat, where distinct throughs in the transmission spectra indicated a high density of cyanobacteria with Chl a and phycobilins, as well as anoxygenic phototrophs with Bchl a and Bchl c (Supplementary Figure S2), with the latter being indicative of the presence of Chloroflexi. The euphotic zone for oxygenic photosynthesis was limited to the uppermost mm of the mat, wherein visible light (PAR, 400–700 nm) was attenuated to ~0.1 μmol photons m-2 s-1 (Figure 4A). Similar optical characteristics were found in samples from the same site by Lassen et al. (1992) >20 years ago.


Microsensor measurements of hydrogen gas dynamics in cyanobacterial microbial mats.

Nielsen M, Revsbech NP, Kühl M - Front Microbiol (2015)

Light and chemical gradients in a coastal cyanobacterial mat under an incident photon irradiance of 500 μmol photons m-2 s-1. (A) Depth profiles of photon scalar irradiance, O2 and H2S concentrations. (B) Depth profiles of pH and H2 concentration. Symbols with error bars for chemical parameters represent the mean ± SD (n = 3).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4508582&req=5

Figure 4: Light and chemical gradients in a coastal cyanobacterial mat under an incident photon irradiance of 500 μmol photons m-2 s-1. (A) Depth profiles of photon scalar irradiance, O2 and H2S concentrations. (B) Depth profiles of pH and H2 concentration. Symbols with error bars for chemical parameters represent the mean ± SD (n = 3).
Mentions: More detailed microenvironmental analyses of H2 dynamics were done in a sulfidic coastal cyanobacterial mat (Supplementary Figure S1A), whereas measurements in coastal sediment with a surface biofilm of diatoms (Supplementary Figure S1B) showed no accumulation of H2 (data not shown). Spectral scalar irradiance measurements showed strong light attenuation with depth in the dense 1–2 mm thick top layer of the coastal mat, where distinct throughs in the transmission spectra indicated a high density of cyanobacteria with Chl a and phycobilins, as well as anoxygenic phototrophs with Bchl a and Bchl c (Supplementary Figure S2), with the latter being indicative of the presence of Chloroflexi. The euphotic zone for oxygenic photosynthesis was limited to the uppermost mm of the mat, wherein visible light (PAR, 400–700 nm) was attenuated to ~0.1 μmol photons m-2 s-1 (Figure 4A). Similar optical characteristics were found in samples from the same site by Lassen et al. (1992) >20 years ago.

Bottom Line: Depletion could be prevented by addition of molybdate pointing to sulfate reduction as a major sink for H2.As soon as O2 from photosynthesis started to accumulate, the H2 was consumed rapidly and production ceased.Our data give detailed insights into the microscale distribution and dynamics of H2 in cyanobacterial biofilms and mats, and further support that cyanobacterial H2 production can play a significant role in fueling anaerobic processes like e.g., sulfate reduction or anoxygenic photosynthesis in microbial mats.

View Article: PubMed Central - PubMed

Affiliation: Section of Microbiology, Department of Bioscience, Aarhus University Aarhus, Denmark.

ABSTRACT
We used a novel amperometric microsensor for measuring hydrogen gas production and consumption at high spatio-temporal resolution in cyanobacterial biofilms and mats dominated by non-heterocystous filamentous cyanobacteria (Microcoleus chtonoplastes and Oscillatoria sp.). The new microsensor is based on the use of an organic electrolyte and a stable internal reference system and can be equipped with a chemical sulfide trap in the measuring tip; it exhibits very stable and sulfide-insensitive measuring signals and a high sensitivity (1.5-5 pA per μmol L(-1) H2). Hydrogen gas measurements were done in combination with microsensor measurements of scalar irradiance, O2, pH, and H2S and showed a pronounced H2 accumulation (of up to 8-10% H2 saturation) within the upper mm of cyanobacterial mats after onset of darkness and O2 depletion. The peak concentration of H2 increased with the irradiance level prior to darkening. After an initial build-up over the first 1-2 h in darkness, H2 was depleted over several hours due to efflux to the overlaying water, and due to biogeochemical processes in the uppermost oxic layers and the anoxic layers of the mats. Depletion could be prevented by addition of molybdate pointing to sulfate reduction as a major sink for H2. Immediately after onset of illumination, a short burst of presumably photo-produced H2 due to direct biophotolysis was observed in the illuminated but anoxic mat layers. As soon as O2 from photosynthesis started to accumulate, the H2 was consumed rapidly and production ceased. Our data give detailed insights into the microscale distribution and dynamics of H2 in cyanobacterial biofilms and mats, and further support that cyanobacterial H2 production can play a significant role in fueling anaerobic processes like e.g., sulfate reduction or anoxygenic photosynthesis in microbial mats.

No MeSH data available.


Related in: MedlinePlus