Electrokinesis is a microbial behavior that requires extracellular electron transport

Area of Science:

• Microbiology
• Bioelectrochemistry
• Bacterial Physiology

Background:

• Shewanella oneidensis MR-1 is a model bacterium for studying extracellular electron transfer (EET).
• Bacterial motility is crucial for nutrient acquisition and colonization, but responses to electrochemical stimuli are not fully understood.

Purpose of the Study:

• To describe and characterize a novel bacterial behavior, electrokinesis, observed in Shewanella oneidensis MR-1.
• To investigate the relationship between electrokinesis, extracellular electron transport, and electrochemical conditions.

Main Methods:

• In situ video microscopy and cell tracking algorithms were used to quantify bacterial swimming speeds and movement patterns.
• Microelectrochemical cells were employed to apply controlled electrical potentials to bacterial cultures.
• Mutant strains deficient in electron transport pathways were utilized to assess the genetic requirements for the observed behavior.

Main Results:

• A previously undescribed bacterial behavior, electrokinesis, was identified, characterized by increased cell swimming speed and altered movement paths near redox-active surfaces.
• Electrokinesis was observed in response to solid MnO(2) reduction and applied positive potentials, and was dependent on functional extracellular electron transport.
• The response was localized to a subpopulation of cells near the electron acceptor and correlated with current generation in microbial fuel cells.

Conclusions:

• Electrokinesis is a novel motility response in Shewanella species, distinct from chemotaxis and galvanotaxis.
• This behavior is contingent upon functional extracellular electron transport and proximity to an electron acceptor.
• Electrokinesis has implications for understanding microbial interactions with mineral surfaces and optimizing microbial electrochemical technologies.