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Updated: Jan 20, 2026
06:03
Procedure for Adaptive Laboratory Evolution of Microorganisms Using a Chemostat
Published on: September 20, 2016
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On the evolution and physiology of cable bacteria
Kasper U Kjeldsen1, Lars Schreiber1,2, Casper A Thorup1,3
1Section for Microbiology & Center for Geomicrobiology, Department of Bioscience, Aarhus University, 8000 Aarhus, Denmark.
Summary
Cable bacteria, filamentous microbes in aquatic sediments, utilize long-distance electron transport to link sulfide oxidation and respiration. Their unique genomes reveal novel genes and metabolic pathways, including carbon dioxide fixation and nitrogen fixation.
Area of Science:
- Microbiology
- Environmental Science
- Genomics
Background:
- Cable bacteria are centimeter-long filaments found in aquatic sediments.
- They perform long-distance electron transport, connecting sulfide oxidation with oxygen or nitrate reduction.
- Pure cultures are unavailable, necessitating alternative genomic approaches.
Purpose of the Study:
- To retrieve draft genomes of marine and freshwater cable bacteria using single-filament genomics and metagenomics.
- To investigate the genomic makeup and unique genes of cable bacteria.
- To elucidate their metabolic pathways, electron transport mechanisms, and unique multicellularity.
Main Methods:
- Single-filament genomics and metagenomics were employed to obtain draft genomes.
- Metaproteomics of a *Ca. Electronema* enrichment was used to support genomic findings.
- Cell-level experimental analyses confirmed predicted metabolic traits.
Main Results:
- Draft genomes of *Candidatus* Electrothrix and *Ca.* Electronema were retrieved.
- Genomes revealed >50% unknown genes but shared core makeup with Desulfobulbaceae, with 212 unique conserved genes.
- Cable bacteria oxidize sulfide via reversed sulfate reduction, fix CO2 using the Wood-Ljungdahl pathway, fix N2, and store polyphosphates/polyglycose.
- A model for electron flow from sulfide to oxygen involving periplasmic components was proposed.
Conclusions:
- Cable bacteria possess unique genomic adaptations for their ecological niche.
- Their metabolism involves sulfide oxidation, CO2 fixation, and N2 fixation.
- A novel model of electron flow and peculiar multicellular energy conservation is proposed.
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