THESIS
2021
1 online resource (xxi, 183 pages) : illustrations (some color)
Abstract
Studying pathogenic viruses requires strict laboratory protocols and sophisticated infrastructure. An
alternative approach is to use surrogate viruses such as bacteriophages. Bacteriophages are viruses that
only infect bacteria. Their specificity makes bacteriophages a promising agent to control bacteria, and
their diversity makes them a promising surrogate for pathogenic viruses. This study focused on these
two properties and used bacteriophage to control bacterial sulfide production and as a surrogate virus
to study how the environment affects virucidal properties.
The first part of this study developed a protocol for harvesting bacteriophages from the environment to
control malodor caused by bacterial hydrogen sulfide (H
2S). The electrostatic interaction of the Ti
4+ and
Al
3+ function...[
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Studying pathogenic viruses requires strict laboratory protocols and sophisticated infrastructure. An
alternative approach is to use surrogate viruses such as bacteriophages. Bacteriophages are viruses that
only infect bacteria. Their specificity makes bacteriophages a promising agent to control bacteria, and
their diversity makes them a promising surrogate for pathogenic viruses. This study focused on these
two properties and used bacteriophage to control bacterial sulfide production and as a surrogate virus
to study how the environment affects virucidal properties.
The first part of this study developed a protocol for harvesting bacteriophages from the environment to
control malodor caused by bacterial hydrogen sulfide (H
2S). The electrostatic interaction of the Ti
4+ and
Al
3+ functionalized materials are reversible and recovered 0.64 ± 0.17% to 67.99±4.79% of
bacteriophage T3. The results showed that both electrostatic interaction and covalent bonding between
metal ions and the amino acids of the viral capsid protein are the primary mechanisms of capture.
Sulfate-reducing bacteria (SRB) were cultured and isolated from Tsuen Wan Harbor and sludge samples
from Stonecutters Island Sewage Treatment Works. Spot titration and plaque assay showed lytic
bacteriophages. The H
2S production of Tsuen Wan SRB was suppressed by 84.66 ± 0.04% and 77.8 ±
0.04% using bacteriophage harvested from dry sludge and the developed protocol, respectively.
In the second part of the study, Plackett-Burman design showed that the most significant factors for
inactivation are mixing speed and chemical agents. Mixing inactivation follows first-order decay. The
inactivation rate constant is a linear function of the friction loss in the system and is significant above
mixing at 100 rpm or a Reynolds number above 2,200. Bacteriophages T3, MS2, and Φ6 were used as
a surrogate for enteric and enveloped, RNA and DNA viruses. Various compounds were screened, but
only Benzalkonium chloride, chlorine dioxide (ClO
2), and Oxone
TM are virucidal at 1,000 mg/L. The minimum inhibitory concentration (MIC) of these compounds against the surrogate viruses is worst in
5% tryptone followed by sludge. The MIC improved in seawater for Oxone
TM and ClO
2 as these
compounds interact with halides to form oxidizing species. These reduced the protein concentration
detected by A280 absorbance, suggesting oxidation of the capsid protein consistent with the literature.
This study showed that bacteriophages can control the H
2S production of SRB and that the media greatly influences the efficacy of virucidal agents. This study is among the first to quantify variations in the
MIC of virucidal agents in environmental samples.
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