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Biological sciences

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Vertical migration in the sediment-dwelling sulfur bacteria Thioploca spp. in overcoming diffusion limitations

Article Abstract:

The filamentous sulfur bacteria Thioploca spp. adjust their vertical positions in the marine shelf sediment according to the concentrations of oxygen, nitrate and sulfide. Experiments showed that an increase in oxygen concentration resulted in a movement into the sediment. Addition of nitrate under anoxic conditions caused a vertical upward movement with the trichomes protruding from the sediment. Addition of sulfide produced a similar response though high levels reversed the response. The ability of the organisms to move between nitrate-rich areas and sulfidic sediments plays a major role in their survival.

Physiological aspects, Oxygen, Bacteria, Nitrates, Sulfur bacteria, Bacterial motility

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Distribution of bacterial populations in a stratified fjord (Mariager Fjord, Denmark) quantified by in situ hybridization and related to chemical gradients in the water column

Article Abstract:

Differences in bacterial populations produce distinct areas of oxygen reduction and sulfide oxidation in the Mariager Fjord, Denmark. The oxic part of the chemocline contains mainly rod-shaped bacteria while the bottom anoxic waters contain ellipsoid bacteria. The bottom waters are anoxic due to the inflow of dense seawater through the inlet of the threshold fjord. However, in situ hybridization shows that the net bacterial concentration is the same throughout the water column. Fluorescent oligonucleotide probes and the digital image analysis can be used to improve the sensitivity of the hybridization.

Denmark, Natural history, Microbial populations, Fjords

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Biogeochemical and molecular signatures of anaerobic methane oxidation in a marine sediment

Article Abstract:

Researchers used a PCR primer based on the dissimilatory sulfate reductase gene to study anaerobic methane oxidation in 6-meter-long cores of marine sediment. A narrow zone of anaerobic methane oxidation was found about 150 cm below the surface.

Methanobacteriaceae, Methanogens

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