Link to the University of Pittsburgh Homepage
Link to the University Library System Homepage Link to the Contact Us Form

The Effect of Noisy Protein Expression on E. coli/Phage Dynamics

Chapman-McQuiston, Emily Louise (2008) The Effect of Noisy Protein Expression on E. coli/Phage Dynamics. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

Primary Text

Download (5MB) | Preview


It has long been suspected that population heterogeneity, either at a genetic level or at a protein level, can improve the fitness of an organism under a variety of environmental stresses. However, quantitative measurements to substantiate such a hypothesis turn out to be rather difficult and have rarely been performed. We examine the response of Escherichia coli (E. coli) to infection by viruses known as phage. In order to inject its DNA into a bacterium, the phage must first bind to a specific receptor protein and consequently the number of receptors per bacterium is related to the bacterial susceptibility to infection. Like many proteins in a bacterial population, the number of expressed receptor proteins in an individual cell is not deterministic but stochastic. In this project, experiments and model calculations are used to study how the noisy expression of phage receptors in a bacterial population changes the short-time population dynamics of an isolated and well-mixed E. coli/phage system. We find that when phage are present in the system, the selective killing of bacteria expressing high numbers of phage receptors creates a phenotype selection and the bacterial population can no longer be considered as having a homogeneous susceptibility to the phage pressure. It is shown that a heterogeneous bacterial population is significantly more fit compared to a homogeneous population when confronting a phage attack. We find that a small percentage of cells which are expressing few phage receptors become important because these bacteria persist despite the presence of phage. In view of their important roles in environmental adaptation, in various diseases and potentially in evolution, a fundamental understanding of this minority of cells remains a significant challenge.


Social Networking:
Share |


Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Chapman-McQuiston, Emily Louiseelc6@pitt.eduELC6
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairWu, Xiao-lunxlwu@pitt.eduXLWU
Committee MemberSwigon, Davidswigon@pitt.eduSWIGON
Committee MemberCoalson, Robertrob@mercury.chem.pitt.eduROBC
Committee MemberDuda, Robertduda@pitt.eduDUDA
Committee MemberSavinov, Vladimirvps3@pitt.eduVPS3
Date: 23 January 2008
Date Type: Completion
Defense Date: 13 November 2007
Approval Date: 23 January 2008
Submission Date: 15 October 2007
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Physics
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: flow cytometry; stochastic protein expression; bacteria; phage
Other ID:, etd-10152007-153219
Date Deposited: 10 Nov 2011 20:03
Last Modified: 15 Nov 2016 13:50


Monthly Views for the past 3 years

Plum Analytics

Actions (login required)

View Item View Item