The dynamics of cable bacteria colonization in surface sediments: a 2D view

Area of Science:

• Geomicrobiology
• Environmental Science
• Biogeochemistry

Background:

• Cable bacteria are electrogenic microorganisms found in sediments.
• Their electron transport capabilities influence diagenesis and elemental cycling.
• Understanding their colonization dynamics is crucial for comprehending sediment processes.

Purpose of the Study:

• To visualize and quantify the spatial and temporal colonization of sediment by cable bacteria in 2D.
• To investigate the development of pH and H2S patterns associated with cable bacteria activity.
• To correlate cell abundance dynamics with observed biogeochemical changes.

Main Methods:

• Utilized planar optical sensors for pH and H2S to map sediment surface.
• Monitored colonization patterns over time in laboratory sediment experiments.
• Analyzed changes in cable bacteria cell abundance in relation to electrogenic activity.

Main Results:

• Sediment surface pH maximum zones developed within 5 days, spreading laterally at 0.3–1.2 cm/day.
• Electrogenic anodic zones (low pH) and H2S heterogeneities expanded with colonization.
• Subsurface cable bacteria abundance increased as electrogenic activity spread, consistent with filament growth.

Conclusions:

• Cable bacteria colonization creates distinct biogeochemical fingerprints (pH-H2S patterns).
• Growth and aggregation are linked to favorable microenvironments and reductant availability (e.g., sulfide).
• Sediment properties and reductant accessibility critically control cable bacteria development and activity.