SENSITIVITY OF STRAINS OF ESCHERICHIA COLI DIFFERING IN REPAIR CAPABILITY TO FAR UV, NEAR UV AND VISIBLE RADIATIONS*

Abstract

Abstract— In stationary phase, strains of Escherichia coli deficient in excision (B/r Her) or recombination repair (K.12 AB2463) were more sensitive than a repair proficient strain (B/r) to monochromatic near‐ultraviolet (365 nm) and visible (460 nm) radiations. The relative increase in sensitivity of mutants deficient in excision or recombination repair, in comparision to the wildtype, was less at 365 nm than at 254 nm. However, a strain deficient in both excision and recombination repair (K12 AB2480) showed a large, almost equal, increase in sensitivity over mutants deficient in either excision or recombination repair at 365 nm and 254 nm. All strains tested were highly resistant to 650 nm radiation. Action spectra for lethality of strains B/r and B/r Her in stationary phase reveal small peaks or shoulders in the 330–340, 400–410 and 490–510 nm wavelength ranges. The presence of 5μg/ml acriflavine (an inhibitor of repair) in the plating medium greatly increased the sensitivity of strain B/r to radiation at 254, 365 and 460 nm, while strains E. coli B/r Her and K12 AB2463 were sensitized by small amounts. At each of the wavelengths tested, acriflavine in the plating medium had at most a small effect on E. coli K.12 AB2480. Acriflavine failed to sensitize any strain tested at 650 nm. Evidence supports the interpretation that lesions induced in DNA by 365 nm and 460 nm radiations play the major role in the inactivation of E. coli by these wavelengths. Single‐strand breaks (or alkali‐labile bonds), but not pyrimidine dimers are candidates for the lethal DNA lesions in uvrA and repair proficient strains. At high fluences lethality may be enhanced by damage to the excision and recombination repair systems.

Photobiology of Low-power Laser Effects

“…In section 3 of this paper, the positive (stimulating) effects of irradiation were described. 3), while a lethal effect is caused by doses of lo6-10' J/m2 (Webb and Brown 1976). These data are summarized for E. coli and mammalian cells in Tables 1 and 2.…”

“…But there exists a tremendous amount of data describing an inhibitory or even lethal effect of visible light (especially blue and fluorescent light) on various types of cells. In both cases, the flavin components of the respiratory chain are discussed as photoacceptors (Tiphlova and Karu 1987a, Webb and Brown 1976). For these negative (inhibitory) effects, the respiratory chain components as primary photoacceptors are discussed (Epel 1973).…”

Influence of Seasonal Environmental Variables on the Distribution of Presumptive Fecal Coliforms around an Antarctic Research Station

“…Antarctic surface seawater at 0°C and 25‰ salinity can contain twice the concentration of dissolved oxygen found in the tropics at 30°C and 35‰ (376.12 compared with 190.74 mol of O 2 kg seawater Ϫ1 ) (7). When oxygen is present, photochemical damage to E. coli is increased at wavelengths found in solar radiation, particularly UVA (36,39,48,49). The combination of UV and oxygen allows the formation of highly reactive free radicals (including singlet oxygen, hydroperoxyl, and hydroxyl groups), which cause cellular damage (47).…”

“…Water depth can influence the effectiveness of solar radiation in fecal coliform inactivation. Action spectra for E. coli show that UVB radiation has the greatest bactericidal effect (48,49), although UVA may be more important in the marine environment, as it penetrates the water column to a greater depth (9). The use of a repair-deficient E. coli strain as a biological dosimeter in Antarctic aquatic environments showed that the majority of cellular damage caused by solar radiation occurred in the top 10 m of the water column (29).…”

Exposure to low UVA doses increases KatA and KatB catalase activities, and confers cross-protection against subsequent oxidative injuries in Pseudomonas aeruginosa

“…Mutant strains of Salmonella enterica lacking alkyl hydroperoxide reductase (ahp) or defective in glutathione synthesis (ghs) have high UVA sensitivity (Kramer & Ames, 1987), and a mutant strain of E. coli defective for both Fe-SOD and Mn-SOD has greater sensitivity to UVA compared with the WT strain (Hoerter et al, 1989). In addition, mutant strains of E. coli deficient in the excision repair system (uvr) are highly sensitive to UVA (Webb & Brown, 1976;Shennan et al, 1996), and similar results were obtained in strains of Salmonella and E. coli defective for RecA, the protein responsible for expression of genes involved in the SOS response (Eisenstark, 1970;Webb & Brown, 1976). The RpoS protein, the alternative sigma transcription factor involved in general stress responses during the stationary growth phase, is also involved in UVA defence both in enterobacteria and Pseudomonas syringae (Miller et al, 2001;Maatouk et al, 2004;Berney et al, 2006b).…”