Effects of bacterial physiology on photoinactivation of pathogens and pathogen indicators
Abstract/Contents
- Abstract
- Surface waters worldwide are increasingly impacted by microbial pollution, with subsequent negative impacts on human health, ecosystem health, and economic stability in communities dependent on surface water resources. In order to prevent human exposure to microbial pollution, surface waters intended for recreational use are regularly monitored for culturable fecal indicator bacteria (FIB). However, relationships between FIB and pathogens are not consistently found in recreational waters, and short time-scale variations in FIB concentrations further complicate the use of daily or weekly measurements to accurately characterize water quality. A better understanding of the fate of microbial pollutants in recreational waters is needed to inform predictive water quality modeling efforts. Photoinactivation is one of the most important factors influencing concentrations of microbial pollutants in clear coastal waters. While many studies have been performed to identify the effects of various water quality and exposure variables on photoinactivation, the importance of specific photoinactivation mechanisms and the effects of cellular characteristics on bacterial photoinactivation remain unclear. The goal of this research is to investigate photoinactivation of pathogenic and indicator bacteria in environmental systems, with a specific focus on the influence of cellular physiology. Chapter 2 investigates the relative importance of oxygen-dependent and oxygen-independent mechanisms on the photoinactivation of Staphylococcus aureus, a pathogenic bacterium of emerging concern. The S. aureus cell membrane remained intact during oxic photoinactivation and was damaged during anoxic photoinactivation, suggesting that oxygen-dependent and oxygen-independent photoinactivation mechanisms target different parts of the S. aureus cell. Chapter 3 builds off of conclusions from Chapter 2 by investigating the global transcriptional response of S. aureus under sunlight stress in both oxic and anoxic conditions. Transcriptional responses were different between oxic and anoxic conditions, and increased expression of hemY in the oxic condition also points to the importance of endogenous photosensitizers on bacterial photoinactivation. Chapter 4 presents a spatial survey of enterococci photoinactivation rates from various environmental sources and investigates the role of source and pigmentation on determining sunlight susceptibility. Photoinactivation rate constants were found to vary over nearly an order of magnitude, and pigmentation had a significant impact on the susceptibility of enterococci to sunlight exposure.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2018; ©2018 |
| Publication date | 2018; 2018 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | McClary, Jill Stephanie |
|---|---|
| Degree supervisor | Boehm, Alexandria |
| Thesis advisor | Boehm, Alexandria |
| Thesis advisor | Criddle, Craig |
| Thesis advisor | Mitch, William A |
| Degree committee member | Criddle, Craig |
| Degree committee member | Mitch, William A |
| Associated with | Stanford University, Civil & Environmental Engineering Department. |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Jill Stephanie McClary. |
|---|---|
| Note | Submitted to the Department of Civil and Environmental Engineering. |
| Thesis | Thesis Ph.D. Stanford University 2018. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2018 by Jill Stephanie McClary
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
Also listed in
Loading usage metrics...