The bactericidal effect of ultraviolet and visible light on Escherichia coli.
The bactericidal radiation dosages at specific wavelengths in the ultraviolet (UV)-visible spectrum are not well documented. Such information is important for the development of new monochromatic bactericidal devices to be operated at different wavelengths. In this study, radiation dosages required to cause mortality of an Escherichia coli strain, ATCC 25922, at various wavelengths between 250 and 532 nm in the UV and visible spectrum were determined. Radiation at 265 nm in the UV region was most efficient in killing the E. coli cells and 100% mortality was achieved at a dose of 1.17 log mJ/cm(2). In the visible spectrum, the radiation dosages required for a one-log reduction of the E. coli cell density at 458 and 488 nm were 5.5 and 6.9 log mJ/cm(2), respectively. However, at 515 and 532 nm, significant killing was not observed at radiation dosage up to 7 log mJ/cm(2). Based on the cell survival data at various radiation dosages between 250 and 488 nm, a predictive equation for the survival of E. coli cells is derived, namely log(S/S(0)) = -(1.089 x 10(7) e(-0.0633lambda))D. The symbols, S(0), S, lambda, and D, represent initial cell density, cell density after irradiation, wavelength of the radiation and radiation dosage, respectively. The proportion of the surviving E. coli cells decreases exponentially with the increase in radiation dosage at a given wavelength. In addition, the radiation dose required for killing a certain fraction of the E. coli cells increases exponentially as the wavelength of radiation increases.
Department of Biology, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario, Canada P7B 5E1.
Natasha
N
Vermeulen
Werden J
WJ
Keeler
Kanavillil
K
Nandakumar
Kam Tin
KT
Leung
D017209:Apoptosis / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D003198:Computer Simulation; D004307:Dose-Response Relationship, Radiation; D004926:Escherichia coli / Q000502:physiology* / Q000528:radiation effects*; D008027:Light; D008954:Models, Biological; D011829:Radiation Dosage; D014466:Ultraviolet Rays