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In Situ Characterization of Shewanella oneidensis MR1 Biofilms by SALVI and ToF-SIMS
Published on: August 18, 2017
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Redox Sensing within the Genus Shewanella
Howard W Harris1, Irene Sánchez-Andrea2, Jeffrey S McLean3,4
1Department of Earth Sciences, Biological Sciences and Physics, University of Southern California, Los Angeles, CA, United States.
Frontiers in Microbiology
|February 10, 2018
Summary
Shewanella bacteria congregate around minerals using extracellular electron transport and chemotaxis genes. Different strains show varied mineral preferences linked to their natural habitats.
Area of Science:
- Microbiology and Microbial Ecology
- Biogeochemistry
- Bacterial Physiology
Background:
- Congregation, a novel bacterial behavior, is defined as cell accumulation around insoluble electron acceptors (IEA) in *Shewanella oneidensis* MR-1.
- This behavior involves coordinated 'run-and-reversal' swimming events, modulated by swimming speed and direction.
- Extracellular electron transport (EET) via outer membrane cytochromes is hypothesized to enable cells to sense their surroundings.
Purpose of the Study:
- To investigate congregation and attachment behaviors in various *Shewanella* strains beyond MR-1.
- To identify genetic factors, specifically EET and chemotaxis genes, correlated with congregation ability.
- To explore strain-specific preferences for different insoluble electron acceptors.
Main Methods:
- Screened wild-type *S. oneidensis* MR-1, deletion mutants, and eight other *Shewanella* strains for congregation.
- Employed specialized cell-tracking techniques to monitor bacterial behavior.
- Utilized a novel cell accumulation after photo-bleaching (CAAP) confocal microscopy technique.
Main Results:
- A strong correlation was found between MR-1's mineral accumulation and the presence of key EET genes (*mtrBC/omcA*) and methyl-accepting protein (MCP) genes with Cache domains.
- *Shewanella putrefaciens* CN32, *S. sp.* ANA-3, and *S. loihica* PV-4 congregated around both Fe(OH)3 and MnO2.
- Other strains exhibited specific mineral preferences (e.g., W3-18-1 for Fe(OH)3, SB2B for MnO2) aligning with their isolation environments.
Conclusions:
- The ability to congregate is linked to specific extracellular electron transport and chemotaxis genes in *Shewanella*.
- Different *Shewanella* species display distinct preferences for insoluble electron acceptors, influenced by their ecological niches.
- This study expands the understanding of *Shewanella* congregation behavior across multiple strains and highlights environmental adaptation.
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