Effects of wavelengths of medium-pressure ultraviolet radiation on photolyase and subsequent photoreactivation

2013 ◽  
Vol 13 (1) ◽  
pp. 158-165 ◽  
Author(s):  
Puay Hoon Quek ◽  
Jiangyong Hu
Keyword(s):  
Escherichia Coli ◽  
Uv Radiation ◽  
Spectrophotometric Assay ◽  
Uv Disinfection ◽  
Direct Effects ◽  
Uv Damage ◽  
Simultaneous Exposure ◽  
Medium Pressure ◽  
Repair Ability ◽  
Polychromatic Radiation

This study aims to investigate the effect of different wavelengths (254, 266, 280 and 365 nm) in polychromatic medium-pressure (MP) UV radiation on the ability of photolyases in repairing dimers and discusses its impact on subsequent photoreactivation. Photolyase was exposed to various doses and irradiances of the UV wavelengths and the dimer repair abilities of the irradiated photolyase were determined via a spectrophotometric assay. At wavelengths below 300 nm, dimer repair rates were not influenced by the UV irradiation between 0.03 and 0.10 mW cm−2. For 365 nm, photolyase exhibited enhanced dimer repair at 0.05 mW cm−2 and then reduced dimer repair with increasing irradiance. In addition, photolyase was found to have decreasing dimer repair rates when exposed to increasing UV doses at all tested wavelengths. Lower photoreactivation levels after MP UV disinfection as compared to low-pressure (LP) UV disinfection was not attributable to a single wavelength in the polychromatic radiation, but is possibly due to the simultaneous exposure of photolyase to a broad spectrum of radiation, which led to a reduction in the dimer repair ability of photolyase. This study is the first to report the direct effects of UV radiation on photolyase enzyme. The data in the study provide some evidence for the mechanism for which MP UV disinfection suppresses photoreactivation in Escherichia coli, which has only been speculated on so far. The knowledge from this study will provide a basis upon which to investigate other enzymes involved in the repair of UV damage to DNA.

scholarly journals Effects of UV Radiation on Photolyase and Implications with Regards to Photoreactivation following Low- and Medium-Pressure UV Disinfection

2007 ◽  
Vol 74 (1) ◽  
pp. 327-328 ◽  
Author(s):  
Jiangyong Hu ◽  
Puay Hoon Quek
Keyword(s):  
Uv Radiation ◽  
Uv Irradiation ◽  
Flavin Adenine Dinucleotide ◽  
Low Pressure ◽  
Uv Disinfection ◽  
Medium Pressure ◽  
Uv Lamps

ABSTRACT Photolyase activity following exposure to low-pressure (LP) and medium-pressure (MP) UV lamps was evaluated. MP UV irradiation resulted in a greater reduction in photolyase activity than LP UV radiation. The results suggest that oxidation of the flavin adenine dinucleotide in photolyase may have caused the decrease in activity.

scholarly journals Potential Repair of Escherichia coli DNA following Exposure to UV Radiation from Both Medium- and Low-Pressure UV Sources Used in Drinking Water Treatment

2002 ◽  
Vol 68 (7) ◽  
pp. 3293-3299 ◽  
Author(s):  
J. L. Zimmer ◽  
R. M. Slawson
Keyword(s):  
Escherichia Coli ◽  
Drinking Water ◽  
Water Treatment ◽  
Uv Radiation ◽  
Drinking Water Treatment ◽  
Low Pressure ◽  
Plate Count ◽  
Treatment Technology ◽  
Medium Pressure ◽  
Uv Lamp

ABSTRACT The increased use of UV radiation as a drinking water treatment technology has instigated studies of the repair potential of microorganisms following treatment. This study challenged the repair potential of an optimally grown nonpathogenic laboratory strain of Escherichia coli after UV radiation from low- and medium-pressure lamps. Samples were irradiated with doses of 5, 8, and 10 mJ/cm2 from a low-pressure lamp and 3, 5, 8, and 10 mJ/cm2 from a medium-pressure UV lamp housed in a bench-scale collimated beam apparatus. Following irradiation, samples were incubated at 37°C under photoreactivating light or in the dark. Sample aliquots were analyzed for up to 4 h following incubation using a standard plate count. Results of this study showed that E. coli underwent photorepair following exposure to the low-pressure UV source, but no repair was detectable following exposure to the medium-pressure UV source at the initial doses examined. Minimal repair was eventually observed upon medium-pressure UV lamp exposure when doses were lowered to 3 mJ/cm2. This study clearly indicates differences in repair potential under laboratory conditions between irradiation from low-pressure and medium-pressure UV sources of the type used in water treatment.

scholarly journals Photoreactivation of Escherichia coli after Low- or Medium-Pressure UV Disinfection Determined by an Endonuclease Sensitive Site Assay

2002 ◽  
Vol 68 (12) ◽  
pp. 6029-6035 ◽  
Author(s):  
Kumiko Oguma ◽  
Hiroyuki Katayama ◽  
Shinichiro Ohgaki
Keyword(s):  
Escherichia Coli ◽  
Uv Irradiation ◽  
Genomic Dna ◽  
Uv Disinfection ◽  
E Coli ◽  
Medium Pressure ◽  
Pyrimidine Dimers ◽  
Sensitive Site ◽  
Uv Lamp

ABSTRACT Photoreactivation of Escherichia coli after inactivation by a low-pressure (LP) UV lamp (254 nm), by a medium-pressure (MP) UV lamp (220 to 580 nm), or by a filtered medium-pressure (MPF) UV lamp (300 to 580 nm) was investigated. An endonuclease sensitive site (ESS) assay was used to determine the number of UV-induced pyrimidine dimers in the genomic DNA of E. coli, while a conventional cultivation assay was used to investigate the colony-forming ability (CFA) of E. coli. In photoreactivation experiments, more than 80% of the pyrimidine dimers induced by LP or MPF UV irradiation were repaired, while almost no repair of dimers was observed after MP UV exposure. The CFA ratios of E. coli recovered so that they were equivalent to 0.9-, 2.3-, and 1.7-log inactivation after 3-log inactivation by LP, MP, and MPF UV irradiation, respectively. Photorepair treatment of DNA in vitro suggested that among the MP UV emissions, wavelengths of 220 to 300 nm reduced the subsequent photorepair of ESS, possibly by causing a disorder in endogenous photolyase, an enzyme specific for photoreactivation. On the other hand, the MP UV irradiation at wavelengths between 300 and 580 nm was observed to play an important role in reducing the subsequent recovery of CFA by inducing damage other than damage to pyrimidine dimers. Therefore, it was found that inactivating light at a broad range of wavelengths effectively reduced subsequent photoreactivation, which could be an advantage that MP UV irradiation has over conventional LP UV irradiation.

Repair and regrowth of Escherichia coli after low- and medium-pressure ultraviolet disinfection

2005 ◽  
Vol 5 (5) ◽  
pp. 101-108 ◽  
Author(s):  
J.Y. Hu ◽  
X.N. Chu ◽  
P.H. Quek ◽  
Y.Y. Feng ◽  
X.L. Tan
Keyword(s):  
Escherichia Coli ◽  
Uv Light ◽  
Bacterial Count ◽  
Uv Disinfection ◽  
Fluorescent Light ◽  
Maximum Increase ◽  
E Coli ◽  
Chlorine Disinfection ◽  
Medium Pressure ◽  
Uv Dose

Ultraviolet (UV) light disinfection has increasingly been used as an alternative method to replace conventional chlorine disinfection as it has been found to be a more efficient disinfection method. As UV disinfection only damages the nucleic acids of the microorganisms to prevent replication, there is a possibility of microorganisms repairing the damage sites. As few studies have investigated the reactivation of microorganisms after exposure to medium-pressure UV disinfection, it is essential for reactivation related to medium-pressure UV disinfection to be studied as medium-pressure lamps are gaining in popularity. Besides, disinfection by-products (DBPs) produced by UV disinfection have been discovered recently and may serve as a carbon source in the finished water, resulting in regrowth of the bacteria. It is therefore important to know the regrowth potential of bacteria with the existence of DBPs. In this study, the repair and regrowth of Escherichia coli after UV disinfection were investigated. Results showed that E. coli underwent photo repair (up to 5 log under fluorescent light conditions) more significantly than dark repair (up to 0.8 log in terms of bacterial count increase). The repair was generally found to be higher at low doses. At the same UV dose, it seems medium-pressure UV irradiation is able to control the repair to a lesser extent. In addition, the bacterial regrowth potential was studied with the addition of DBPs typically found in UV processes, such as acetic acid and formaldehyde. The maximum increase in bacterial count was found to be 0.3 log. Generally, the level of regrowth was insignificant compared with the increase of bacterial count due to bacterial repair.

Photoreactivation of Escherichia coli following medium-pressure ultraviolet disinfection and its control using chloramination

2006 ◽  
Vol 53 (6) ◽  
pp. 123-129 ◽  
Author(s):  
P.H. Quek ◽  
J.Y. Hu ◽  
X.N. Chu ◽  
Y.Y. Feng ◽  
X.L. Tan
Keyword(s):  
Escherichia Coli ◽  
Uv Disinfection ◽  
Fluorescent Light ◽  
Ultraviolet Disinfection ◽  
Bench Scale ◽  
Medium Pressure ◽  
Entire Duration ◽  
Collimated Beam ◽  
Synthetic Water

Ultraviolet (UV) disinfection is becoming increasingly popular as an alternative disinfection technology to chlorination in recent years. In this study, we investigated the photoreactivation of Escherichia coli following medium-pressure (MP) UV disinfection of synthetic water by a bench-scale collimated beam apparatus. The UV doses ranged from 1.6 –19.7 mWs/cm2 and photoreactivation was investigated for 6 hours under fluorescent light. In addition, chloramination was applied after UV disinfection to investigate its ability to control photoreactivation. It was found that photoreactivation occurred for all UV doses tested and the increase in bacteria numbers ranged from 0.04 to 1.35 log10. However, the degree of photoreactivation decreased with increased UV doses. Chloramination experiments revealed that the addition of 0.5 mg/l of monochloramine resulted in suppression of photoreactivation for 1 hour only. An increased monochloramine dose of 1 mg/l was found to prevent photoreactivation for the entire duration of the experiment. The results of this study have shown that photoreactivation occurs even after MP UV disinfection, although it is of a lesser extent at higher UV doses. This study has also established that secondary chloramination can effectively suppress and eliminate photoreactivation with a chloramine dose of 1 mg/l.

UV disinfection of stabilization pond effluent: a feasible alternative for areas with land restriction

2012 ◽  
Vol 65 (2) ◽  
pp. 247-253 ◽  
Author(s):  
C. V. P. Alves ◽  
C. A. L. Chernicharo ◽  
M. von Sperling
Keyword(s):  
Escherichia Coli ◽  
Uv Radiation ◽  
Suspended Solids ◽  
Domestic Wastewater ◽  
Low Pressure ◽  
Uasb Reactor ◽  
Uv Disinfection ◽  
Total Coliforms ◽  
Stabilization Pond ◽  
Feasible Alternative

The purpose of this research was to determine the feasibility of a UV photoreactor for the disinfection of effluent from a polishing pond following a UASB reactor treating domestic wastewater. For this, a 20 mm diameter photoreactor (20.7 litre volume) equipped with four 30 W submerged low-pressure mercury arc lamps was used. Three tests with contact times and doses ranging from 45 to 90 s and from 16.9 to 31.3 mW s cm−2 were carried out. Inactivation of total coliforms and Escherichia coli varied from 2.6 to 3.4 log-units, even with the presence of suspended solids in the range of 87 to 102 mg L−1. These results have shown that UV radiation disinfection of pond effluents can be a feasible alternative in areas with land restriction.

UV inactivation and characteristics after photoreactivation of Escherichia coli with plasmid: Health safety concern about UV disinfection

2012 ◽  
Vol 46 (13) ◽  
pp. 4031-4036 ◽  
Author(s):  
Meiting Guo ◽  
Jingjing Huang ◽  
Hongying Hu ◽  
Wenjun Liu ◽  
Jian Yang
Keyword(s):  
Escherichia Coli ◽  
Safety Concern ◽  
Uv Disinfection ◽  
Health Safety

scholarly journals Solar UV damage to cellular DNA: from mechanisms to biological effects

2018 ◽  
Vol 17 (12) ◽  
pp. 1842-1852 ◽  
Author(s):  
Leon H. F. Mullenders
Keyword(s):  
Dna Replication ◽  
Uv Radiation ◽  
Biological Effects ◽  
Uv Damage ◽  
Solar Uv ◽  
Cellular Dna ◽  
Solar Ultraviolet

Solar ultraviolet (UV) radiation generates bulky photodimers at di-pyrimidine sites that pose stress to cells and organisms by hindering DNA replication and transcription.

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