Phenotypic Switching of Bacterial Cells in Extreme Environments
Student: Sudip Nepal
Degree: Ph.D., July 2020
Major Professor: Dr. Pradeep Kumar
Research Area(s):
Biological Materials & Processes
Modeling & Simulation
Background/Relevance
- While there are studies on the cellular response of bacteria under continuous environmental stress, cellular response under temporal fluctuations of environmental stress poorly explored.
- Biological switches in response to external perturbations allow cells to change to different phenotypes that can withstand environmental stress.
Innovation
- Stochastic switching is a survival strategy under environmental stress. This study will explore phenotypic switching of bacteria under extreme environmental fluctuations, such as pressure, salinity, and pH using experimental and theoretical approaches.
Approach
- Fluorescence and phase contrast images of bacteria grown in different environments are acquired and analyzed to characterize different phenotypes.
- Stochastic switching of the cells at fluctuating pressure is explained using a new model for cell division in conjunction with with 2-state behavior of the cells.
- Time-lapse movies of the cells are obtained and analyzed to investigate the cell division of a heterogeneous population of phenotypes.
Key Results
- Bacterial cells exhibit phenotypic switching at high pressure and high salinity, and these phenotypes are reversible upon the removal of the applied stress.
- Cells exhibit plasmolysis at high MgSO4 concentration, and the plasmolysis is stronger at poles.
- The genes involved in sulfate transport and osmotic response are upregulated at high concentration of magnesium sulfate.
Conclusions
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Bacteria switch to a new phenotype at high pressure and salinity that is reversible upon removal of pressure and salt stresses.
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At high salinity, cells undergo plasmolysis. The gene involved in sulfate transport and an osmotically inducible gene are upregulated at 1.25 M MgSO4.
Future Work
- Investigate the adaptation of bacteria in stressed conditions at laboratory time scales.