Differences In UV Sensitivity Research Articles

UV Tolerance of Spoilage Microorganisms and Acid-Shocked and Acid-Adapted Escherichia coli in Apple Juice Treated with a Commercial UV Juice-Processing Unit

The enhanced thermal tolerance and survival responses of Escherichia coli O157:H7 in acid and acidified foods is a major safety concern for the production of low-pH products, including beverages. Little is known about this phenomenon when using UV light treatments. This study was conducted to evaluate the effects of strain (E. coli O157:H7 strains C7927, ATCC 35150, ATCC 43895, and ATCC 43889 and E. coli ATCC 25922) and physiological state (control-unadapted, acid adapted, and acid shocked) on the UV tolerance of E. coli in apple juice treated under conditions stipulated in current U.S. Food and Drug Administration regulations. A greater than 5-log reduction of E. coli was obtained under all tested conditions. A significant effect of strain (P < 0.05) was observed, but the physiological state did not influence pathogen inactivation (P ≥ 0.05). The UV sensitivity of three spoilage microorganisms (Aspergillus niger, Penicillium commune, and Alicyclobacillus acidoterrestris) was also determined at UV doses of 0 to 98 mJ/cm(2). Alicyclobacillus was the most UV sensitive, followed by Penicillium and Aspergillus. Because of the nonsignificant differences in UV sensitivity of E. coli in different physiological states, the use of an unadapted inoculum would be adequate to conduct challenge studies with the commercial UV unit used in this study at a UV dose of 14 mJ/cm(2). The high UV tolerance of spoilage microorganisms supports the need to use a hurdle approach (e.g., coupling of refrigeration, preservatives, and/or other technologies) to extend the shelf life of UV-treated beverages.

Intraspecific variations in growth, yield and photosynthesis of sorghum varieties to ambient UV (280–400 nm) radiation

A field study was conducted to investigate the impact of ambient solar UV on the various growth, physiological and yield parameters of four sorghum (Sorghum bicolor L.) varieties—Indore-12, Indore-26, CSV-23 and Indore-27 by excluding either UV-B (<315nm) or UV-A/B (<400nm) components of solar spectrum. Exclusion of UV significantly enhanced plant height, area and specific leaf weight of flag leaf, biomass accumulation, yield parameters and harvest index in all the sorghum varieties. Chlorophyll b was significantly enhanced and chlorophyll a increased to a lesser extent, UV-B absorbing substances and chlorophyll a/b ratio were significantly decreased by the exclusion of solar UV. The enhancement in the vegetative growth and yield by UV exclusion might be linked to the remarkable increase in rate of photosynthesis in sorghum varieties. The magnitude of the response was high in I-26 and I-27 as compared to CSV-23 and I-12 after exclusion of solar UV. All the varieties of sorghum had a negative cumulative stress response index (CSRI), the sensitivity of the sorghum varieties was in the following sequence I-12>CSV-23>I-26>I-27. Thus I-27 was the most sensitive and I-12 the least sensitive variety to present level of solar UV radiation. The differences in UV sensitivity identified among sorghum varieties might be useful in breeding programs for increased tolerance to UV-B radiation.

Does UV-B Radiation Affect Embryos of Three High Elevation Amphibian Species in California?

Abstract Declines and extinctions of amphibians in well-protected habitats suggest that global atmospheric factors may be responsible. We tested effects of field exposures of ultraviolet radiation (UV-B) on embryo hatching success and time to hatching in three anurans that inhabit high elevation areas of the Sierra Nevada in California, USA. While few obvious environmental impacts have occurred in the high elevation area of the Sierra Nevada, two of the three most common anurans, the Yosemite Toad (Bufo canorus) and the Southern Mountain Yellow-legged Frog (Rana muscosa), have suffered severe population declines while the sympatric Pacific Treefrog (Pseudacris regilla) has remained relatively abundant. Previous studies have shown that hatching of P. regilla embryos at lower elevations are not affected negatively by UV-B radiation. We hypothesized that differences in UV sensitivity may help explain why P. regilla remain abundant while B. canorus and R. muscosa have declined sharply. We conducted field expe...

Temperature dependence of UV radiation effects in Arctic and temperate isolates of three red macrophytes

The temperature dependence of UV effects was studied for Arctic and temperate isolates of the red macrophytes Palmaria palmata, Coccotylus truncatus and Phycodrys rubens. The effects of daily repeated artificial ultraviolet B and A radiation (UVBR: 280–320 nm, UVAR: 320–400 nm) treatments were examined for all isolates at 6, 12 and 18 °C by measuring growth, optimal quantum yield of PSII (Fv/Fm) and cyclobutane-pyrimidine dimer (CPD) accumulation. Furthermore, possible ecotypic differences in UV sensitivity between Arctic and temperate isolates were evaluated. Large species-specific differences in UV sensitivity were observed for all parameters: the lower subtidal species C. truncatus and P. rubens were highly sensitive to the UV treatments, whereas P. palmata, which predominantly occurs in the upper subtidal zone, was not affected by these treatments. Only minor differences were found between Arctic and temperate isolates, suggesting that no differences in UV sensitivity have evolved in these species. Relative growth rates were temperature-dependent, whereas species-specific UV effects on growth rates were relatively independent of temperature. In contrast, the species-specific decrease in Fv/Fm and its subsequent recovery were temperature-dependent in all species. UV effects on Fv/Fm were lower at 12 and 18 °C compared with 6 °C. In addition, UV effects on Fv/Fm decreased in the course of the experiment at all temperatures, indicating acclimation to the UV treatments. CPDs accumulated during the experiment in both isolates of P. rubens, whereas CPD concentrations remained low for the other two species. CPD accumulation appeared to be independent of temperature. The results suggest that summer temperatures occurring in temperate regions facilitate repair of UV-induced damage and acclimation to UV radiation in these algae compared with Arctic temperatures. Because the differences in UV effects on Fv/Fm, growth and CPD accumulation were relatively small over a broad range of temperatures, it was concluded that the influence of temperature on UV effects is small in these species.

Intercellular contact-dependent survival of human A549, NCI-H596 and NCI-H520 non-small cell lung carcinoma cell lines.

In the present study, we examined the relationship between cell phenotype and cell survival of three human non-small cell lung carcinoma cell lines (A549, NCI-H596 and NCI-H520). Cells in exponential growth at various densities were incubated for 24 h at 37 degrees C in a 5% CO2 humidified atmosphere and then exposed to UV radiation for 1 min (256 nm, 40 W, source-to-target distance 100 cm). After two days the surviving cells were quantified by sulforhodamine beta staining and DNA fragmentation assay. The differences in UV sensitivity at 60 x 10(3) cells/cm2 among the cell lines were not related to the proliferative state of the cells but to the extent of intercellular contact. In contrast to A549 and NCI-H596, irradiated NCI-H520 cells presented lower DNA fragmentation and an aggregated cell culture phenotype even prior to confluence, suggesting that a contact-effect mechanism provides further protection against UV radiation.

Survivorship of Cyclops abyssorum tatricus (Cyclopoida, Copepoda) and Boeckella gracilipes (Calanoida, Copepoda) under ambient levels of solar UVB radiation in two high-mountain lakes

We performed in situ experiments during the summer of 1995 and 1996 to assess the potential effect of solar ultraviolet B (UVB) radiation (290-320 nm) on the survival of Cyclops abyssorum tatricus Kozminski and Boeckella gracilipes Daday. These species are numerically dominant within the crustacean zooplankton living in two high-mountain lakes, one located in the Austrian Alps (Gossenkollesee (GKS), 2417 m above sea level, maximum depth 9.9 m) and another in the Chilean Andes (Laguna Negra, 2700 m above sea level, maximum depth 320 m). The copepods were incubated in quartz tubes (1 l) or in quartz tubes wrapped with Mylar D® to exclude most of the UVB radiation. The organisms were exposed at 0.5 m depth for 10-72 h on cloudless days. Both lakes were very transparent to UVB and 10% of the surface radiation at the nominal wavelength of 305 nm was still present at 9.6 m in GKS and at 12.8 m in Laguna Negra. These species migrate verti- cally and have a maximum daytime distribution close to the bottom (C.abyssorum tatricus) or below 15 m depth (B.gracilipes). Both species were red, but the carotenoid concentration was higher in C.abyssorum tatricus than in B.gracilipes (6.5 and 2.3 µg mg-1 dry weight, respectively). UV-absorbing compounds with a maximum absorption at ~334 nm were also detected. Cyclops abyssorum tatricus was highly resistant to UVB radiation and no significant lethal effect was observed. Boeckella gracilipes had a mortality ~5 times higher in the treatment receiving full sunlight than in the Mylar treatment (3.2%) only when exposed for 70 h. The resistance of B.gracilipes was higher than that reported in the literature for the same species, suggesting the existence of intraspecific differences in UV sensitivity.

Characterization of the rad142 Mutant of Saccharomyces cerevisiae: Implications for the Recognition of UV Photoproducts by the Rad14 Protein

The RAD14 gene of Saccharomyces cerevisiae is required for the incision step of the nucleotide excision repair process. The Rad14 protein can bind zinc, possesses a potential zinc finger DNA binding domain and has been shown to bind specifically to damaged DNA. Differences in UV sensitivity exist between a rad14 deletion strain and a putative rad14 point mutant, the point mutant being more resistant to UV than the deletion strain. Here, we confirm that the rad14 deletion strain repairs neither UV-induced cyclobutane pyrimidine dimers (CPDs) nor endonuclease III-sensitive damage sites, whereas the point mutant cannot repair the former but can repair the latter. From this it can be inferred that the point mutant produces an altered protein product allowing recognition of endonuclease III sensitive sites but not CPDs. To investigate this, the rad14 mutant allele was sequenced. It contained two GC-AT transition mutations when compared to the wild-type RAD14 gene sequence. When the rad14 point mutant sequence is translated, alterations within the putative zinc finger binding domain are observed, with one of the cysteine residues of the zinc binding motif being replaced by tyrosine. This suggests that alterations within the zinc finger binding domain of the Rad14 protein cause changes to the damage recognition properties of the protein. The use of the Rad14 protein from the point mutant should assist in experiments investigating the in vitro binding properties of the Rad14 protein to different types of DNA damage. © 1997 by John Wiley & Sons, Ltd.

Characterization of the rad14-2 mutant of Saccharomyces cerevisiae: implications for the recognition of UV photoproducts by the Rad14 protein.

The RAD14 gene of Saccharomyces cerevisiae is required for the incision step of the nucleotide excision repair process. The Rad14 protein can bind zinc, possesses a potential zinc finger DNA binding domain and has been shown to bind specifically to damaged DNA. Differences in UV sensitivity exist between a rad14 deletion strain and a putative rad14 point mutant, the point mutant being more resistant to UV than the deletion strain. Here, we confirm that the rad14 deletion strain repairs neither UV-induced cyclobutane pyrimidine dimers (CPDs) nor endonuclease III-sensitive damage sites, whereas the point mutant cannot repair the former but can repair the latter. From this it can be inferred that the point mutant produces an altered protein product allowing recognition of endonuclease III sensitive sites but not CPDs. To investigate this, the rad14 mutant allele was sequenced. It contained two GC-AT transition mutations when compared to the wild-type RAD14 gene sequence. When the rad14 point mutant sequence is translated, alterations within the putative zinc finger binding domain are observed, with one of the cysteine residues of the zinc binding motif being replaced by tyrosine. This suggests that alterations within the zinc finger binding domain of the Rad14 protein cause changes to the damage recognition properties of the protein. The use of the Rad14 protein from the point mutant should assist in experiments investigating the in vitro binding properties of the Rad14 protein to different types of DNA damage.

Plasmid-associated sensitivity of Bacillus thuringiensis to UV light

Spores and vegetative cells of Bacillus thuringiensis were more sensitive to UV light than were spores or cells of plasmid-cured B. thuringiensis strains or of the closely related Bacillus cereus. Introduction of B. thuringiensis plasmids into B. cereus by cell mating increased the UV sensitivity of the cells and spores. Protoxins encoded by one or more B. thuringiensis plasmids were not involved in spore sensitivity, since a B. thuringiensis strain conditional for protoxin accumulation was equally sensitive at the permissive and nonpermissive temperatures. In addition, introduction of either a cloned protoxin gene, the cloning vector, or another plasmid not containing a protoxin gene into a plasmid-cured strain of B. thuringiensis all increased the UV sensitivity of the spores. Although the variety of small, acid-soluble proteins was the same in the spores of all strains examined, the quantity of dipicolinic acid was about twice as high in the plasmid-containing strains, and this may account for the differences in UV sensitivity of the spores. The cells of some strains harboring only B. thuringiensis plasmids were much more sensitive than cells of any of the other strains, and the differences were much greater than observed with spores.

The repair of UV-irradiated plasmids transfected into cultured fish cells

UV-irradiated plasmids (pNPV B and pBSCATSV) were transfected into RBCF-1 cells derived from a goldfish (Carassius auratus) and into a xeroderma pigmentosum (group A) cell line, XP20SSV. The frequency of stable neor transformation by pNPV B decreased in a dose-dependent manner. However, in spite of large differences in UV sensitivity detected in the colony formation assay, the dose-response curves of RBCF-1 cells and XP20SSV cells were almost the same. The photorecovery (PR) of transforming activity of UV-irradiated plasmids was confirmed in RBCF-1 cells but its extent was much smaller than that observed in the survival assay. The expression of the transfected cat (chloramphenicol acetyltransferase; CAT) gene after 24-h incubation in the dark was much more sensitive to UV irradiation when compared with the stable transformation assay. The extent of PR of cat gene expression in RBCF-1 cells was high and comparable with that of the survival assay. The CAT value of RBCF-1 cells transfected with UV-irradiated plasmids relative to that of unirradiated controls increased as incubation time in the dark after transfection became longer. This suggests that the UV lesions on the plasmids transfected in the RBCF-1 cells were repaired in the dark. The cat gene expression of UV-irradiated plasmids in XP20SSV was very low and independent of incubation time after transfection.

Increased UV sensitivity of Escherichia coli cells after introduction of foreign photolyase genes

High-expression plasmids for photolyase (phr) genes from the bacteria Escherichia coli, Anacystis nidulans, Streptomyces griseus and Halobacterium halobium and the yeast Saccharomyces cerevisiae were constructed and introduced into E. coli phr recA cells. As previously reported, all introduced phr genes provided the host cells with photoreactivation-repair activity and the introduced E. coli phr gene rendered the host cells more UV-resistant in the dark. E. coli cells harboring foreign phr genes, however, were found to be more sensitive to UV light in the dark than cells containing the vector plasmid only. These differences in UV sensitivity in the dark disappeared when the host cells had an additional mutation, uvrA, suggesting that the foreign photolyases inhibited the E. coli excision-repair system.

Effects of ultraviolet radiation on carotenoid containing and albino strains of Neurospora crassa

To determine the influence of carotenoids on UV sensitivity of Neurospora crassa conidia, the dose-response curves of 3 albino strains were compared to that of the wild type. In a control experiment the genetic background effects were eliminated by irradiating the wild type in which carotenoid synthesis had been inhibited by β-ionone, and comparing the dose-response curve to that of untreated wild type. All strains used had similar γ-ray survival curves and nuclei per conidium which precluded differences in UV sensitivity due to morphological differences. The albinos and β-ionone-treated strains showed a greater sensitivity (mean LD50 4.35·103 erg/mm2) to UV irradiation than the wild type (LD50 7.30·103 erg/mm2).

Effects of ultraviolet radiation on carotenoid-containing and albino strains of Neurospora crassa.

Abstract To determine the influence of carotenoids on UV sensitivity of Neurospora crassa conidia, the dose-response curves of 3 albino strains were compared to that of the wild type. In a control experiment the genetic background effects were eliminated by irradiating the wild type in which carotenoid synthesis had been inhibited by β-ionone, and comparing the dose-response curve to that of untreated wild type. All strains used had similar γ-ray survival curves and nuclei per conidium which precluded differences in UV sensitivity due to morphological differences. The albinos and β-ionone-treated strains showed a greater sensitivity (mean LD50 4.35·10 3 erg/mm 2 ) to UV irradiation than the wild type (LD50 7.30·10 3 erg/mm 2 ).

Ultraviolet Radiation Sensitivity of White Mutants and Red Wild-Type Serratia marcescens

White mutants of Serratia marcescens, which do not produce the nonessential pigment prodigiosin, were found to be more resistant to killing by ultraviolet light (UV) than the red-wild type. Pigment induction in a white mutant, which sensitizes to gamma rays, does not change this mutant's UV resistance. Therefore, prodigiosin does not appear to sensitize to UV killing in these strains. Possible differences in UV sensitivity due to UV-induced lysis and filament formation were checked, but not observed. Post-UV plating of red and white Serratia on caffeine and acriflavin was found to decrease the survival for both strains, reflecting the probable existence of repair.

Strain Sensitivity of Silkworm Eggs to Killing and Mutation by Ultraviolet Light

Killing and mutation by ultraviolet light was compared among different x-ray-sensitive silkworm strains. After mature oocytes and eggs at early cleavage stages were irradiated with varying doses of UV, embryonic mortality and mutation frequency at pe:re egg-color-specific loci were measured. Strain differences in UV sensitivity were found for both effects on oocytes as well as on eggs: for killing, the difference between the most resistant and sensitive strains was four to six times, and for mutation induction was seven times. A consistent positive correlation was found between sensitivity to killing and sensitivity to mutation induction. No positive correlation was found between UV and x-ray sensitivities for either biological effect. In treated oocytes, more fractional-body than whole-body mutations were induced by UV, while more whole-body than fractional-body mutations were induced by x-rays.

On the control of UV-sensitivity of phage T4 by the gene x

Abstract DNA of UV-irradiated phages T4 v+x+, T4 v1x+, T4 v+x, and T4 v1x was used for competitive inhibition of photo-enzymatic repair (photoreactivation) in vitro of UV-irradiated transforming DNA of Haemophilus influenzae. At a given UV-dose and at a given DNA concentration, the competitive power of all four DNA species was identical, indicating the presence of equal numbers of photorepairable UV-lesions in all cases. It is concluded that the quality and quantity of the primary UV-effects are identical for these four phage types, although they exhibit considerable differences in UV-sensitivity and in the extent of photoreactivation. Hence, not only the v gene, but also the x gene, controls the UV-sensitivity of phage by intracellular alteration of the UV-irradiated DNA. This conclusion is consistent with the results of rII+ marker rescue experiments, showing that the extent of rescue is always lower if the unirradiated parental phages carry the x rather than the x+ allele. A plausible explanation for these results is the control by the x gene of the frequency of genetic recombination, which is shown independently in crosses between unirradiated rII phages. To explain the increased UV-sensitivity of single-infecting T4 x phage, it is tentatively assumed that the x allele, in contrast to the x+ allele, does not permit a repair process which has some mechanism in common with genetic recombination. An alternative explanation would be that the x mutation concerns more than one gene. Additional experiments were carried out to study the superposition of the x gene effect with v gene repair and photo-enzymatic repair in marker rescue.

Mutants of phage T4 with increased sensitivity to ultraviolet

After treatment of phage T4 with nitrous acid, three independent mutants with increased UV sensitivity have been isolated. The survival curves of two of them, both in darkness and under conditions of maximum photoreactivation, are very similar to those of phage T2. Genetic crosses have shown that the mutations had occurred in the v cistron (formerly called u cistron), which controls the differences in UV sensitivity and photoreactivability between T4 and T2; therefore, these two mutants are called v 1 and v 2. The third mutation, producing a sensitivity level intermediate between T4 and T2, concerns a cistron called x which is not closely linked to v and affects UV sensitivity by a still unknown mechanism. In the recombinant v 1 x, the effects are additive, leading to a UV sensitivity considerably higher than that of T2. Thus, there are now available in phage T4 four sensitivity levels, represented by the genotypes v + x + (wild type), v + x, v x +, and v x, with relative sensitivities of 0.45, 0.75, 1.0, and 2.0, respectively. The slopes of the multicomplex survival curves obtained with the different sensitivity types do not show any simple correlation with the slopes of the monocomplex survival curves. Further, the multicomplex curves of the mutants have shoulders considerably lower than those of T4 and T2 wild type.