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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

Long-term measurements of H2 and O2 concentration at 0.8 mm depth in a hypersaline cyanobacterial mat sample incubated under a 14 h light (800 μmol photons m-2 s-1) and 10 h dark cycle.
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Figure 3: Long-term measurements of H2 and O2 concentration at 0.8 mm depth in a hypersaline cyanobacterial mat sample incubated under a 14 h light (800 μmol photons m-2 s-1) and 10 h dark cycle.

Mentions: Long-term experiments with simultaneous O2 and H2 measurements over several days (14 h dark: 10 h light) with the microsensor tips positioned 0.8 mm below the mat surface, i.e., in the zone of maximal O2 production in the light, showed recurrent H2 production that persisted in the anoxic mat throughout the 14 h dark incubation period (Figure 3). Quantification of H2 production in Lyngbya aestuarii and M. chtonoplastes cultures showed similar long term persistence for >24 h (Kothari et al., 2014). The build-up of H2 was highest immediately after darkening and then leveled off after 1–2 h. Strong H2 depletion occurred rapidly after onset of the illumination leading to O2 accumulation from photosynthesis. Such depletion can be explained by several mechanisms such as (i) O2 inhibition of H2 production coupled with diffusive losses, (ii) H2 consumption with O2, by e.g., Knallgas bacteria, and/or intermittent anoxygenic photosynthesis. However, our limited experimental data do not allow us to discriminate between the relative importance of these H2 consuming processes.


Microsensor measurements of hydrogen gas dynamics in cyanobacterial microbial mats.

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

Long-term measurements of H2 and O2 concentration at 0.8 mm depth in a hypersaline cyanobacterial mat sample incubated under a 14 h light (800 μmol photons m-2 s-1) and 10 h dark cycle.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 3: Long-term measurements of H2 and O2 concentration at 0.8 mm depth in a hypersaline cyanobacterial mat sample incubated under a 14 h light (800 μmol photons m-2 s-1) and 10 h dark cycle.
Mentions: Long-term experiments with simultaneous O2 and H2 measurements over several days (14 h dark: 10 h light) with the microsensor tips positioned 0.8 mm below the mat surface, i.e., in the zone of maximal O2 production in the light, showed recurrent H2 production that persisted in the anoxic mat throughout the 14 h dark incubation period (Figure 3). Quantification of H2 production in Lyngbya aestuarii and M. chtonoplastes cultures showed similar long term persistence for >24 h (Kothari et al., 2014). The build-up of H2 was highest immediately after darkening and then leveled off after 1–2 h. Strong H2 depletion occurred rapidly after onset of the illumination leading to O2 accumulation from photosynthesis. Such depletion can be explained by several mechanisms such as (i) O2 inhibition of H2 production coupled with diffusive losses, (ii) H2 consumption with O2, by e.g., Knallgas bacteria, and/or intermittent anoxygenic photosynthesis. However, our limited experimental data do not allow us to discriminate between the relative importance of these H2 consuming processes.

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