Journal ArticleDOI
Pure singlet oxygen cytotoxicity for bacteria
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TLDR
Physical separation of the photosensitizer and the bacteria eliminates the possibility of direct interaction between bacteria and photoexcited sensitizers that could lead to Type I (non‐singlet oxygen) photooxidation processes, which was used to examine the bacterial cytotoxicity of singlet oxygen.Abstract:
We have modified the separated-surface-sensitizer singlet oxygen generating system previously described (Midden and Wang, 1983) for the efficient exposure to pure singlet oxygen of bacteria collected on membrane filters. Physical separation of the photosensitizer and the bacteria eliminates the possibility of direct interaction between bacteria and photoexcited sensitizers that could lead to Type I (non-singlet oxygen) photooxidation processes. This system was used to examine the bacterial cytotoxicity of singlet oxygen. The role of singlet oxygen was confirmed by measuring the decrease in cytotoxicity as the distance between the singlet oxygen source and the bacteria was increased. The gas phase half-life of the intermediate responsible for cell killing, determined from this distance dependence analysis (24 ± 6 ms), is the same as that calculated from literature data for the gas phase half-life of singlet oxygen (53 ± 37 ms). Killing of various strains of Salmonella lyphimurium and Escherichia coli was compared at the same dose of singlet oxygen. Bacteria were killed by singlet oxygen at levels several orders of magnitude lower than those effective in killing by H2O2. Altered DNA repair capacities (uvrB, recA, xth, nth, pKM101) did not affect survival. Incomplete cell wall lipopolysaccharide formation decreased survival following singlet oxygen exposure. Overproduction of the singlet oxygen quencher histidine increased survival, as did accumulation of the dipeptide carnosine (β-alanyl-L-histidine). No evidence for mutagenicity of exogenous singlet oxygen exposure was obtained in a variety of S. typhimurium strains killed to 35% survival.read more
Citations
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Photochemical mechanisms of light-triggered release from nanocarriers
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Effect of cell-photosensitizer binding and cell density on microbial photoinactivation.
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Polycationic photosensitizer conjugates: effects of chain length and Gram classification on the photodynamic inactivation of bacteria
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References
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Acetylornithinase of Escherichia coli: partial purification and some properties.
Henry J. Vogel,David M. Bonner +1 more
TL;DR: Compounds Used-N”l-Acetyl-n-ornithine was synthesized as previously described and L-Ornithine monohydrochloride was obtained from the Mann Research Laboratories.
Journal Article
Identification of singlet oxygen as the cytotoxic agent in photoinactivation of a murine tumor
TL;DR: The protective effect against photodynamic inactivation of the TA-3 cells afforded by 1,3-diphenylisobenzofuran coupled with the nearly quantitative formation of the singlet oxygen-trapping product indicates that Singlet oxygen is the probable agent responsible for toxicity in this system.
Journal ArticleDOI
An improved bacterial test system for the detection and classification of mutagens and carcinogens
TL;DR: A test that compares mutagenic killing in deep rough strains with and without DNA excision repair, and a test using forward mutagenesis in a deep rough strain lacking excison repair are described.
Journal ArticleDOI
Positive Control of a Regulon for Defenses against Oxidative Stress and Some Heat-Shock Proteins in Salmonella typhimurium
TL;DR: The oxyR regulatory network is a previously uncharacterized global regulatory system in enteric bacteria that is resistant to a variety of oxidizing agents and overexpresses at least five enzyme activities involved in defenses against oxidative damage.
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