Photoinactivation of bacteria : effects of physiology, water conditions, and sunlight intensity
Abstract/Contents
- Abstract
- Declining water quality along the world's coastlines threatens ecosystems and human health. Exposure to coastal waters polluted with pathogens from wastewater causes in excess of 120 million gastrointestinal and 50 million severe respiratory illnesses globally each year. In those coastal environments, field observations suggest sunlight is one of the most important factors modulating pathogen concentrations; however, there is an imperfect understanding of the extent to and the manner in which sunlight damage the pathogens. This dissertation aimed to link several physical and biological factors to the decay efficacy of bacteria by sunlight. The findings from this dissertation will improve our ability to forecast fecal indicator bacteria concentrations, design proper mitigation strategies for pathogenic bacteria, and overall reduce risk to public health. The work for the dissertation was organized into five research chapters. The first research chapter focused on the potential of the yellow carotenoid pigment in Enterococcus to provide protection from sunlight, first through field observations then through direct laboratory measurements. The second research chapter further explored the biological factors affecting photoinactivation, where it was found that the physiological state of the Enterococcus faecalis cells upon the application of the solar irradiation affected the photoinactivation kinetics. The work presented in the third and fourth research chapters began to link some biological factors with the physical factors of the water, specifically the presence of exogenous photosensitizers. These two chapters use a wide range of health relevant bacteria (8), photosensitizers (5), and types of sunlight (2), which allowed for a greater breadth of analysis. Through this greater breadth, it was found that the bacterial membrane, photosensitizer properties, and degree of UVB light intensity determined the contribution of the exogenous mechanism to the overall bacterial photoinactivation. The last research chapter started to bridge the gap between the laboratory and the field, finding that a simple linear regression model based on UVB light intensity could largely predict inactivation rate constants in natural waters of any depth and absorbance. Taken together, the results form this work provide insight into the mechanisms of photoinactivation, potential applications of models to predict photoinactivation kinetics, and design factors for engineered systems utilizing sunlight.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2016 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Maraccini, Peter Andrew |
|---|---|
| Associated with | Stanford University, Department of Civil and Environmental Engineering. |
| Primary advisor | Boehm, Alexandria |
| Thesis advisor | Boehm, Alexandria |
| Thesis advisor | Luthy, Richard G |
| Thesis advisor | Mitch, William A |
| Advisor | Luthy, Richard G |
| Advisor | Mitch, William A |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Peter Andrew Maraccini. |
|---|---|
| Note | Submitted to the Department of Civil and Environmental Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2016. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2016 by Peter Andrew Maraccini
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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