Evidence Regarding the UV Sunscreen Role of a Mycosporine-Like Compound in the Cyanobacterium Gloeocapsa sp

The UV sunscreen role commonly ascribed to mycosporine-like amino acids (MAAs) was investigated with an isolate of the terrestrial cyanobacterium Gloeocapsa sp. strain C-90-Cal-G.(2), which accumulates intracellularly an MAA with absorbance maximum at 326 nm but produces no extracellular sunscreen compound (i.e., scytonemin). The intracellular concentrations of MAA achieved were directly related to the intensity of the UV radiation (maximum at 320 nm) received by the cells. However, the presence of high concentrations of MAA was not necessary for the physiological acclimation of the cultures to UV radiation. The measured sunscreen factor due to MAA in single cells was 0.3 (the MAA prevented 3 out of 10 photons from hitting potential cytoplasmic targets). High contents of MAA in the cells correlated with increased resistance to UV radiation. However, when resistance was gauged under conditions of desiccation, with inoperative physiological photoprotective and repair mechanisms, cells with high MAA specific contents were only 20 to 25% more resistant. Although UV radiation centered around both 320 and 365 nm resulted in chlorophyll a photobleaching and photoinhibition of photosynthesis, the difference in sensitivity correlated with MAA accumulation occurred only at 320 nm (absorbed by MAA) and not at 365 nm (not absorbed by MAA). This difference represents the maximal protection ascribable to the presence of MAA for single cells, i.e., if one does not consider the enhancing effects of colony formation on protection by sunscreens.     

UV Light Inactivation of Bacterial Biothreat Agents

Seven species of bacterial biothreat agents were tested for susceptibility to UV light (254 nm). All gram-negative organisms tested required <12 mJ/cm² for a 4-log₁₀ reduction in viability (inactivation). Tailing off of the B. anthracis spore inactivation curves began close to the 2-log₁₀ inactivation point, with a fluence of approximately 40 mJ/cm², and 3-log₁₀ inactivation still was not achieved with a fluence of 120 mJ/cm².The security of our nation''s water supply is a concern for water providers and public health officials. Questions have been asked regarding the possibility of our drinking water becoming contaminated with biothreat agents and the efficacy of current disinfection practices for the reduction in viability (inactivation) of biothreat agents (5, 8, 14). The use of UV irradiation as a supplemental water disinfection practice is increasing for several reasons, among them improving control of protozoa, such as Cryptosporidium spp., and decreasing disinfection by-products created by chemical disinfectants (21). This study employed a bench-scale collimated beam test to determine the UV fluence (dose) required to inactivate seven representative bacterial biothreat agents.Seven species, two isolates each, from the Health and Human Services and U.S Dept. of Agriculture lists of select agents (http://www.selectagents.gov/resources/List%20of%20Select%20Agents%20and%20Toxins_111708.pdf) were used in this study: Bacillus anthracis Ames spores, B. anthracis 34F2 (Sterne) spores, Brucella melitensis ATCC 23456, B. melitensis IL195, Brucella suis KS528, B. suis MO562, Burkholderia mallei M9, B. mallei M13, Burkholderia pseudomallei ATCC 11688, B. pseudomallei CA650, Francisella tularensis LVS, F. tularensis NY98, Yersinia pestis A1122, and Y. pestis Harbin. B. anthracis was grown on soil extract-peptone-beef extract agar (SEA) (1) or in Schaeffer''s sporulation medium (SSM) (10) for 7 days, resulting in >99% spores as determined by phase-contrast microscopy. The cells and spores were then washed by centrifugation (8,000 × g), resuspended in ultrapure water, transferred to centrifuge tubes, treated with 50% ethanol for 1 h at room temperature, and washed five times with sterile ultrapure water before being stored in reverse-osmosis water at −70°C. F. tularensis isolates were grown on cysteine heart agar (1) and all other isolates on Trypticase soy agar with 5% sheep blood (TSA II; Becton Dickinson Microbiology Systems, Sparks, MD) for 24 h before testing. B. anthracis spores were adjusted to 10⁷ CFU/ml and other bacterial suspensions to 10⁸ CFU/ml in Butterfield buffer (3 mM KH₂PO₄, pH 7.2; Becton Dickinson Microbiology Systems), and then isolates were sonicated (40-Hz ultrasonic cleaner; VWR, Suwanee, GA) for 1 min to disperse aggregates. The suspensions were diluted 1:100 in Butterfield buffer for final test concentrations. Five milliliters of each suspension were placed into a small petri dish (50-mm diameter) along with a small sterile stir bar, and the petri dish was placed on a stir plate.UV irradiation was performed by using a collimated beam apparatus (Calgon Carbon, Pittsburgh, PA) equipped with a low-pressure lamp (254 nm) according to the standard method developed by Bolton and Linden (2). The surface of the suspension was placed 5 cm from the end of the collimating tube. The UV intensity was measured with a radiometer at 0.5-cm intervals across the test area and variability compensated for according to the UVCalc software directions (International UV association [http://www.iuva.org]). The fluences (UV doses) were determined using the UVCalc software, and the petri dishes were placed under the beam for at least five time periods to deliver a range of appropriate fluences to the organisms. Each irradiation test was conducted at room temperature (23 ± 2°C) in triplicate and in a random order of fluences. After exposure, 10-fold serial dilutions were performed, and the dilutions were spread plated in triplicate. Plates were placed in a dark incubator within 10 min of plating and incubated at the temperature appropriate for the organism, and the colonies were counted at 24 h and 48 h for B. anthracis and at 3 and 5 days for the remaining organisms. Colonies were counted, and the log₁₀ inactivation at each fluence was determined for each organism. A linear regression of the fluence response data determined the fluence required for 2-, 3-, and 4-log₁₀ inactivation.The UV fluences required for inactivation of each organism are reported in Table ​Table1.1. Little difference in UV susceptibility was seen between the gram-negative organisms. B. suis KS528 and B. melitensis ATCC 23456 required the greatest UV fluence of the gram-negative organisms for 4-log₁₀ inactivation (10.5 and 10.2 mJ/cm², respectively), while the two Y. pestis isolates required the lowest UV fluence (4.1 and 4.9 mJ/cm²) for the same 4-log₁₀ inactivation (Table ​(Table1).1). Generally, the two isolates of each species differed no more than 3 mJ/cm² in the UV fluence required for 4-log₁₀ inactivation.

TABLE 1.

UV fluence required for given log₁₀ inactivation of each organism

Development of a Nucleoside Analog UV Light Sensor

Abstract

Conjugation of the photosensitive nucleoside ( E )-5-(2-methoxycarbonylethenyl)cytidine to biotin provided a means to attach this analogue to microparticles for dosimetry applications that require uv sensor mobility.     

Assessment of the Effectiveness of Low-Pressure UV Light for Inactivation of Helicobacter pylori

Three strains of Helicobacter pylori were exposed to UV light from a low-pressure source to determine log inactivation versus applied fluence. Results indicate that H. pylori is readily inactivated at UV fluences typically used in water treatment regimens. Greater than 4-log₁₀ inactivation was demonstrated on all three strains at fluences of less than 8 mJ cm⁻².     

Comparative Inactivation of Adenovirus Serotypes by UV Light Disinfection

The results of this study confirm that adenoviruses are the most resistant enteric viruses to inactivation by UV light and that adenovirus 40 appears to be the most resistant. The effect of freeze-thawing and storage in water may affect the sensitivity of some adenoviruses to inactivation by UV light.     

苦丁茶防晒组分萃取工艺的可视化分析

对采用超声辅助法萃取苦丁茶防晒组分进行了较为系统的研究。选择萃取时间、萃取剂体积分数、萃取温度、样品细度4个主要影响因素,运用多因素多水平可视化设计法安排实验。以防晒光区的紫外吸收面积值作为防晒组分萃取含量的实验评定指标。用自主提出的多因素多水平实验结果可视化分析方法对多维空间实验数据进行分析。得出当ρ(苦丁茶)=0.20 g/L时,最佳工艺范围为萃取时间30～60 min、萃取剂体积分数φ(C2H5OH)为50%～70%、萃取温度50～65℃、萃取样品细度140～160目。     

Comparative Inactivation of Enteroviruses and Adenovirus 2 by UV Light

The doses of UV irradiation necessary to inactivate selected enteric viruses on the U.S. Environmental Protection Agency Contaminant Candidate List were determined. Three-log reductions of echovirus 1, echovirus 11, coxsackievirus B3, coxsackievirus B5, poliovirus 1, and human adenovirus type 2 were effected by doses of 25, 20.5, 24.5, 27, 23, and 119 mW/cm², respectively. Human adenovirus type 2 is the most UV light-resistant enteric virus reported to date.     

Modulating the Structure of EGFR with UV Light: New Possibilities in Cancer Therapy

The epidermal growth factor receptor (EGFR) is a member of the ErbB family of receptor tyrosine kinases. EGFR is activated upon binding to e.g. epidermal growth factor (EGF), leading to cell survival, proliferation and migration. EGFR overactivation is associated with tumor progression. We have previously shown that low dose UVB illumination of cancer cells overexpressing EGFR prior to adding EGF halted the EGFR signaling pathway. We here show that UVB illumination of the extracellular domain of EGFR (sEGFR) induces protein conformational changes, disulphide bridge breakage and formation of tryptophan and tyrosine photoproducts such as dityrosine, N-formylkynurenine and kynurenine. Fluorescence spectroscopy, circular dichroism and thermal studies confirm the occurrence of conformational changes. An immunoassay has confirmed that UVB light induces structural changes in the EGF binding site. A monoclonal antibody which competes with EGF for binding sEGFR was used. We report clear evidence that UVB light induces structural changes in EGFR that impairs the correct binding of an EGFR specific antibody that competes with EGF for binding EGFR, confirming that the 3D structure of the EGFR binding domain suffered conformational changes upon UV illumination. The irradiance used is in the same order of magnitude as the integrated intensity in the solar UVB range. The new photonic technology disables a key receptor and is most likely applicable to the treatment of various types of cancer, alone or in combination with other therapies.     

Ultraviolet-B Wavelengths Regulate Changes in UV Absorption of Cleaner Fish Labroides dimidiatus Mucus

High-energy wavelengths in the ultraviolet-B (UVB, 280-315 nm) and the UVA (315-400-nm) portion of the spectrum are harmful to terrestrial and aquatic organisms. Interestingly, UVA is also involved in the repair of UV induced damage. Organisms living in shallow coral reef environments possess UV absorbing compounds, such as mycosporine-like amino acids, to protect them from UV radiation. While it has been demonstrated that exposure to UV (280-400 nm) affects the UV absorbance of fish mucus, whether the effects of UV exposure vary between UVB and UVA wavelengths is not known. Therefore, we investigated whether the UVB, UVA, or photosynthetically active radiation (PAR, 400-700 nm) portions of the spectrum affected the UV absorbance of epithelial mucus and Fulton’s body condition index of the cleaner fish Labroides dimidiatus. We also compared field-measured UV absorbance with laboratory based high-performance liquid chromatography measurements of mycosporine-like amino acid concentrations. After 1 week, we found that the UV absorbance of epithelial mucus was higher in the UVB+UVA+PAR treatment compared with the UVA+PAR and PAR only treatments; after 2 and 3 weeks, however, differences between treatments were not detected. After 3 weeks, Fulton’s body condition index was lower for fish in the UVB+UVA+PAR compared with PAR and UVA+PAR treatments; furthermore, all experimentally treated fish had a lower Fulton’s body condition index than did freshly caught fish. Finally, we found a decrease with depth in the UV absorbance of mucus of wild-caught fish. This study suggests that the increase in UV absorbance of fish mucus in response to increased overall UV levels is a function of the UVB portion of the spectrum. This has important implications for the ability of cleaner fish and other fishes to adjust their mucus UV protection in response to variations in environmental UV exposure.     

Effect of UV Light on RNA-Directed DNA Polymerase Activity of Murine Oncornaviruses

The UV inactivation of RNA-directed DNA polymerase activity of Rauscher leukemia virus was shown to be due to damage to the protein. The UV dose resulting in 37% survival of viral polymerase activity at 254 nm was 2.4 × 10⁴ to 3.1 × 10⁴ ergs/mm². The inactivation rate of p30, a major internal viral protein, was much slower.     

Treatment of Platelet Products with Riboflavin and UV Light: Effectiveness Against High Titer Bacterial Contamination

Contamination of platelet units by bacteria has long been acknowledged as a significant transfusion risk due to their post-donation storage conditions. Products are routinely stored at 22 °C on an agitating shaker, a condition that can promote bacterial growth. Although the total number of bacteria believed to be introduced into a platelet product is extremely low, these bacteria can multiply to a very high titer prior to transfusion, potentially resulting in serious adverse events. The aim of this study was to evaluate a riboflavin based pathogen reduction process against a panel of bacteria that have been identified as common contaminants of platelet products. This panel included the following organisms: S. epidermidis, S. aureus, S. mitis, S. pyogenes, S. marcescens, Y. enterocolitica, B. neotomae, B. cereus, E. coli, P. aeruginosa and K. pneumoniae. Each platelet unit was inoculated with a high bacterial load and samples were removed both before and after treatment. A colony forming assay, using an end point dilution scheme, was used to determine the pre-treatment and post-treatment bacterial titers. Log reduction was calculated by subtracting the post-treatment titer from the pre-treatment titer. The following log reductions were observed: S. epidermidis 4.7 log (99.998%), S. aureus 4.8 log (99.998%), S. mitis 3.7 log (99.98%), S. pyogenes 2.6 log (99.7%), S. marcescens 4.0 log (99.99%), Y. enterocolitica 3.3 log (99.95%), B. neotomae 5.4 log (99.9996%), B. cereus 2.6 log (99.7%), E. coli ≥5.4 log (99.9996%), P. aeruginosa 4.7 log (99.998%) and K. pneumoniae 2.8 log (99.8%). The results from this study suggest the process could help to lower the risk of severe adverse transfusion events associated with bacterial contamination.     

Red Light Stimulates Feeding Motivation in Fish but Does Not Improve Growth

Nile tilapia fish were individually reared under similar light levels for 8 weeks under five colored light spectra (maximum wavelength absorbance): white (full light spectrum), blue (∼452 nm), green (∼516 nm), yellow (∼520 nm) or red (∼628 nm). The effects of light on feeding, latency to begin feeding, growth and feed conversion were measured during the last 4 weeks of the study (i.e., after acclimation). We found that red light stimulates feeding, as in humans, most likely by affecting central control centers, but the extra feeding is not converted into growth.     

Delayed Colony Formation in Diploid Cells of Various Genotypes after UV Light Irradiation

Russian Journal of Genetics - Experimental curves of the dependence of survival and delayed colony formation on UV light (254 nm) fluence for two wild-type strains of diploid yeast Saccharomyces...     

UV Light Inactivation of Human and Plant Pathogens in Unfiltered Surface Irrigation Water

Fruit and vegetable growers continually battle plant diseases and food safety concerns. Surface water is commonly used in the production of fruits and vegetables and can harbor both human- and plant-pathogenic microorganisms that can contaminate crops when used for irrigation or other agricultural purposes. Treatment methods for surface water are currently limited, and there is a need for suitable treatment options. A liquid-processing unit that uses UV light for the decontamination of turbid juices was analyzed for its efficacy in the treatment of surface waters contaminated with bacterial or oomycete pathogens, i.e., Escherichia coli, Salmonella enterica, Listeria monocytogenes, Clavibacter michiganensis subsp. michiganensis, Pseudomonas syringae pv. tomato, and Phytophthora capsici. Five-strain cocktails of each pathogen, containing approximately 10⁸ or 10⁹ CFU/liter for bacteria or 10⁴ or 10⁵ zoospores/liter for Ph. capsici, were inoculated into aliquots of two turbid surface water irrigation sources and processed with the UV unit. Pathogens were enumerated before and after treatment. In general, as the turbidity of the water source increased, the effectiveness of the UV treatment decreased, but in all cases, 99.9% or higher inactivation was achieved. Log reductions ranged from 10.0 to 6.1 and from 5.0 to 4.2 for bacterial pathogens and Ph. capsici, respectively.     

207-nm UV Light - A Promising Tool for Safe Low-Cost Reduction of Surgical Site Infections. I: In Vitro Studies

Background

0.5% to 10% of clean surgeries result in surgical-site infections, and attempts to reduce this rate have had limited success. Germicidal UV lamps, with a broad wavelength spectrum from 200 to 400 nm are an effective bactericidal option against drug-resistant and drug-sensitive bacteria, but represent a health hazard to patient and staff. By contrast, because of its limited penetration, ∼200 nm far-UVC light is predicted to be effective in killing bacteria, but without the human health hazards to skin and eyes associated with conventional germicidal UV exposure.

Aims

The aim of this work was to test the biophysically-based hypothesis that ∼200 nm UV light is significantly cytotoxic to bacteria, but minimally cytotoxic or mutagenic to human cells either isolated or within tissues.

Methods

A Kr-Br excimer lamp was used, which produces 207-nm UV light, with a filter to remove higher-wavelength components. Comparisons were made with results from a conventional broad spectrum 254-nm UV germicidal lamp. First, cell inactivation vs. UV fluence data were generated for methicillin-resistant S. aureus (MRSA) bacteria and also for normal human fibroblasts. Second, yields of the main UV-associated pre-mutagenic DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts) were measured, for both UV radiations incident on 3-D human skin tissue.

Results

We found that 207-nm UV light kills MRSA efficiently but, unlike conventional germicidal UV lamps, produces little cell killing in human cells. In a 3-D human skin model, 207-nm UV light produced almost no pre-mutagenic UV-associated DNA lesions, in contrast to significant yields induced by a conventional germicidal UV lamp.

Conclusions

As predicted based on biophysical considerations, 207-nm light kills bacteria efficiently but does not appear to be significantly cytotoxic or mutagenic to human cells. Used appropriately, 207-nm light may have the potential for safely and inexpensively reducing surgical-site infection rates, including those of drug-resistant origin.