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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

(A) Concentration profiles of H2 in a hypersaline microbial mat as a function of time after darkening. (B) Concentration profiles of H2 and O2 measured after 15 min darkness. The mat sample was incubated 2.5 h under a photon irradiance of 1800 μmol photons m-2 s-1 prior to darkening.
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Figure 2: (A) Concentration profiles of H2 in a hypersaline microbial mat as a function of time after darkening. (B) Concentration profiles of H2 and O2 measured after 15 min darkness. The mat sample was incubated 2.5 h under a photon irradiance of 1800 μmol photons m-2 s-1 prior to darkening.

Mentions: We note that the absolute amount of H2 produced in the mats after darkening apparently depended on the irradiance level during the previous light incubation. When we increased the irradiance to 1800 μmol photons m-2 s-1 for 2.5 h we again saw a very strong O2 accumulation in the sample but observed a much higher H2 production reaching ~2% H2 15 min after onset of darkness. Maximal levels of 40–50 μM (8–9% H2) were reached in the upper millimeters of the mat within 30 min after darkening (Figure 2A). These H2 levels are higher than most other findings in more permanently submerged hypersaline mats that generally exhibit lower H2 accumulation than intertidal mats (Table 1).


Microsensor measurements of hydrogen gas dynamics in cyanobacterial microbial mats.

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

(A) Concentration profiles of H2 in a hypersaline microbial mat as a function of time after darkening. (B) Concentration profiles of H2 and O2 measured after 15 min darkness. The mat sample was incubated 2.5 h under a photon irradiance of 1800 μmol photons m-2 s-1 prior to darkening.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 2: (A) Concentration profiles of H2 in a hypersaline microbial mat as a function of time after darkening. (B) Concentration profiles of H2 and O2 measured after 15 min darkness. The mat sample was incubated 2.5 h under a photon irradiance of 1800 μmol photons m-2 s-1 prior to darkening.
Mentions: We note that the absolute amount of H2 produced in the mats after darkening apparently depended on the irradiance level during the previous light incubation. When we increased the irradiance to 1800 μmol photons m-2 s-1 for 2.5 h we again saw a very strong O2 accumulation in the sample but observed a much higher H2 production reaching ~2% H2 15 min after onset of darkness. Maximal levels of 40–50 μM (8–9% H2) were reached in the upper millimeters of the mat within 30 min after darkening (Figure 2A). These H2 levels are higher than most other findings in more permanently submerged hypersaline mats that generally exhibit lower H2 accumulation than intertidal mats (Table 1).

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