Date of Graduation

7-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Microelectronics-Photonics (PhD)

Degree Level

Graduate

Department

Microelectronics-Photonics

Advisor/Mentor

Kumar, Pradeep

Committee Member

Balachandran, Kartik

Second Committee Member

Li, Jiali

Third Committee Member

Shew, Woodrow L.

Fourth Committee Member

Wise, Rick L.

Keywords

Bacteria; Europa and Mars; Extreme environmental conditions; High pressure; High salt; Phenotypic switching

Abstract

A large number of terrestrial microbial lives thrive in extremes of environmental conditions, including extremes of pressure, temperature, salinity, pH, and a combination of them. For example, all the marine biomass thrive at high hydrostatic pressure depending on depth. The temperature in the ocean can be very high near the hydrothermal vents and salinity and pH depends on the composition of salt in the surrounding areas. On the surface, hot springs, lakes and geysers provide high temperature conditions, while many places are permafrost regions with subzero temperatures. There is an emerging body of work on the viability, genomics, and metagenomics of these organisms, also called extremophiles due to their love for extremes of physicochemical conditions. However, these studies only provide a small window into their adaptation. A better insight into their adaptation to these conditions can be obtained by investigating the effect of these environments on cellular processes of mesophiles, organisms that are not adapted to extremes. Usually, extremes of environmental conditions lead to stresses on mesophilic cells, and therefore, application of these environments may reveal the bottleneck cellular processes that are prone to fail. The effect of pressure, temperature, and salinity on various cellular processes including metabolisms, growth, cell division, and gene expression of a mesophilic bacterium, Escherichia coli was studied. This work provides a quantitative picture of these cellular processes of phenotypes obtained under different extremes, and sets a foundation for long-term laboratory evolution of a mesophilic bacterium to the extremes of environmental conditions. Furthermore, the results presented here are also useful in assessing the kind of microbial lifeforms that may exist elsewhere in our solar system, such as Mars, Europa, Ceres, and Enceladus, where the presence of liquid water is known.

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