TitleResponses in E. coli to combinatorial stress treatments
(HCl, EDTA, H2O2, and CuSO4)
NameMiddler, Steven (author), Roche, Alex (chair), Palenchar, Peter (internal member), Martin, Joseph (internal member), Rutgers University, Camden Graduate School,
DescriptionAll living organisms adapt to their environment through a series of biochemical responses. Escherichia coli (E. coli) have a plethora of different enzymes, sigma factors, and other biomolecules that assist in stress relief. These experiments showed that E. coli have stress responses for individual stresses. These stress responses are not always additive when exposed to multiple stress factors.
Many times an individual stress response is triggered to counteract a single environmental change. Sometimes this same stress response will aid the cells with a different, unrelated stress. When both stresses are present, more of this stress response will materialize as a response to both stresses and will help prevent too much damage to the cell. This is called "cross-protection" of stress. After seeing the results of these experiments, it is believed that E. coli has some global stress responses and many of the biomolecules used to fight stress are involved in cross-protection of multiple stresses.
These results were generated using a method where E. coli were grown onto control agar plates as well as plates treated with small concentrations of lethal substances. Using a technique called "Blue/White Screening" and colony counting software, the amount of colonies grown overnight on these plates could be counted. The area of the colonies and the relative amount of β-galactosidase transcribed and translated could also be measured. The control plates and treated plates were compared using these three criteria. The different individual stresses were also compared.
Plates were also treated with combinations of the same stresses and compared to the single treatment plates. Much of the data collected indicated a difference in E. coli's responses to an individual stress and how E. coli would be expected to react if the stress responses were additive. This proves that there was some cross-protection taking place in some instances.
Changes in distributions were also examined for each set of plates in order to examine the effect of the stresses on the stochastic nature of E. coli growth and functional protein production. Differences were noticed when comparing the distributions of control plates and stress plates. Differences were seen in different types and combinatorial stressors as well.
The second half of the experiments done here focused on using high performance liquid chromatography to find differences in concentration of molecules in E. coli extracts that were treated with hydrogen peroxide for a brief amount of time and control E. coli extracts not put under any stress. This experiment proved to be too inconsistent to learn any facts. There was an issue with the chemistry involved in the E. coli extracts reactions with the indicator molecules used to find free thiols and free amines in the extracts.
NoteIncludes bibliographical references (p. 171-184)
Noteby Steven Middler
CollectionCamden Graduate School Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.