Cable bacteria colonise new sediment environments through water column dispersal

Area of Science:

• Microbiology
• Environmental Science
• Biogeochemistry

Background:

• Cable bacteria are globally distributed filamentous microorganisms.
• They possess a unique metabolism enabling long-distance electron transport, crucial for sediment elemental cycling.
• Oxygen inhibits cable bacteria, presenting a challenge for dispersal through oxygenated aquatic environments.

Purpose of the Study:

• To investigate the dispersal mechanisms of marine cable bacteria in oxygenated conditions.
• To understand how cable bacteria colonize new environments despite oxygen sensitivity.

Main Methods:

• A compartmentalized microcosm experiment was designed.
• Cable bacteria were cultured in natural sediment ('source') and their activity monitored in sterilized sediment ('destination') exposed to oxygenated seawater.
• Filament fragments ('snippets') and their association with sediment particles were analyzed.

Main Results:

• Cable bacteria successfully colonized destination cores over weeks, with each core containing a single strain.
• Filament 'snippets' (approx. 15 cells) were found in the microcosm water.
• Approximately 30% of these snippets were attached to sediment particles, suggesting a protective association.
• Snippet release was also observed in natural salt marsh environments.

Conclusions:

• A model for cable bacteria dispersal in oxygenated waters was proposed, involving filament breakage into snippets.
• These snippets are released into the water column and transported, likely protected by sediment particles.
• This dispersal strategy contributes to microbial community assembly and prokaryotic biogeography in marine sediments.