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Electrical and Electrochemical dynamics during germination and outgrowth of bacterial spores

Primary Supervisor: Dr Munehiro Asally, School of Life Sciences

Secondary supervisor: Dr Chris Rodrigues

PhD project title: Electrical and Electrochemical dynamics during germination and outgrowth of bacterial spores

University of Registration: University of Warwick

Project outline:

Bacterial spores are a highly resilient and stable form of life. They can resist against extreme environments and almost all kinds of stresses ‒from UV and gamma irradiation to heat and toxic chemicals. Because of this property, spores are used for the studies in astrobiology as they can likely survive interplanetary and terrestrial-planet environments (Nicholson, 2020). In our society, spores hold a threat to food security as they can survived a sterilisation process (Wells-Bennik et al., 2016).

Whilst spores are metabolically inactive, they can revive to become active upon exposure to nutrients (Christie and Setlow, 2020). Spores maintain the for an extended period ‒in an extreme instance, 250-million years old spores were shown to germinate and start to replicate by addition of nutrient in a laboratory environment. (To give you a context, dinosaur extinction was ‘only’ 66 million years ago.) One of the unique features of bacterial spores, with respect to vegetative cells, is that spores are dehydrated and accumulate different kinds of cationic ions. In fact, cation efflux and hydration are the initial step of spore germination. Ion and water flux implies that electrical and osmotic interactions play important roles. However, the biophysical principle and mechanism of this process is not very well understood.

This project will investigate the dynamics of ion flux and membrane electrical potential during spore germination and outgrowth. The project will use the Gram-positive model bacterium, Bacillus subtilis. The gained understanding will be used to engineer and control the process. The project will mainly use fluorescence time-lapse microscopy and single-cell quantitative image analysis using artificial neural network. It will offer a training opportunity for biophysical and microbiology experiments and data analysis. To control the process, electrical stimulation and ion-channel targeting chemicals will be used. A simple phenomenological model will be developed to understand the obtained experimental data.

Key recent relevant publications from Asally lab:

  • Benarroch JM & Asally M (2020) “The Microbiologist’s Guide to Membrane Potential Dynamics.” Trends in Microbiology 28, 304–314.
  • Sirec T, Benarroch JM, Buffard P, Garcia-Ojalvo J, Asally M (2019) “Electrical Polarization Enables Integrative Quality Control during Bacterial Differentiation into Spores.” iScience 16, 378–389.
  • Stratford JP, Edwards CLA, Ghanshyam MJ, Malyshev D, Delise MA, Hayashi Y, Asally M (2019) “Electrically induced bacterial membrane-potential dynamics correspond to cellular proliferation capacity.” Natl. Acad. Sci. 116, 9552–9557.

BBSRC Strategic Research Priority: Understanding the Rules of Life:Microbiology & Systems Biology

Techniques that will be undertaken during the project:

  • Fluorescence time-lapse microscopy
  • Plate reader assay
  • Molecular cloning
  • Microbiology
  • Image analysis
  • Convolutional neural network image segmentation
  • Bacterial electrophysiology

Contact: Dr Munehiro Asally, University of Warwick