Phenotypic Switching of Bacterial Cells in Extreme Environments
Student: Sudip Nepal
Degree: Ph.D., July 2020
Major Professor: Dr. Pradeep Kumar
Biological Materials & Processes
Modeling & Simulation
- 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.
- 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.
- 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.
- 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.
Bacteria switch to a new phenotype at high pressure and salinity that is reversible upon removal of pressure and salt stresses.
At high salinity, cells undergo plasmolysis. The gene involved in sulfate transport and an osmotically inducible gene are upregulated at 1.25 M MgSO4.
- Investigate the adaptation of bacteria in stressed conditions at laboratory time scales.