AHCBAU 33 (6) 573-644
`(2005)
`ISSN 0323-4320 - Vol. 33
`No. 6 - December 2005
`4
`Official Jounal ofthe.Water
`Chemical Society — a Division
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`Acta
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`CoverIllustration: Pool water activities — a challenge for treatment and hygiene (see also this issue, pp. 585-594).
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`€
`

`

`AHCBAU33 (6) 573-644
`(2005)
`ISSN 0323-4320 - Vol. 33
`No. 6 - December 2005
`
`A\cirochimicaet
`Ave.robiologica
`
`
`
`Contents
`
`M. ClauB, R. Mannesmann,
`A. Kolch
`
`T. Glauner, F. Kunz,
`Cc. Zwiener, F. H. Frimmel
`
`K. Michel, B. Ludwig
`
`A. Ostojié, S. Curéié,
`L. Comié, M. Topuzovic
`
`J. Flores-Burgos,
`Ss. S. S. Sarma, S. Nandini
`
`Fges,
`“>
`
`5
`PWILEY
`InterScience’
`DIsCOVER BOMITTHING GRdaT
`
`579
`
`585
`
`595
`
`605
`
`614
`
`Research Papers
`
`Photoreactivation of Escherichia coli and Yersinia enterolytica after
`Irradiation with a 222 nm Excimer Lamp Compared to a 254 nm Low-
`pressure Mercury Lamp
`Photoreaktivierung von Escherichia coli und Yersinia enterolytica nach
`Bestrahlung mit einem 222 nm-Excimerstrahler im Vergleich mit einem
`254 nm-Niederdruck-Quecksilberstrahler
`
`Elimination of Swimming Pool Water Disinfection By-products with
`Advanced Oxidation Processes (AOPs)
`Verringerung von Desinfektionsnebenprodukten bei der Schwimm-
`beckenwasseraufbereitung
`durch
`erweiterte Oxidationsverfahren
`(AOP — Advanced Oxidation Processes)
`,
`
`Modelling of Seepage Water Composition from Experimentswith an Acid
`Soil and a Caicareous Sediment
`
`Modellierung der Sickerwasserzusammensetzung ausgehend von
`Experimenten mit einem sauren Boden und einem kalkhaltigen Sedi-
`ment
`
`Estimate of the Eutrophication Process in the Gruza Reservoir (Serbia
`and Montenegro)
`Einschatzung des Eutrophierungsprozesses im Stausee von Gruza
`(Serbien und Montenegro)
`
`Effect of Single Species or Mixed Algal (Chlorella vulgaris and Scene-
`desmus acutus) Diets on the Life Table Demography of Brachionus
`calyciflorus and Brachionus patulus (Rotifera: Brachionidae)
`Die Wirkung einer Diat von einzelnen oder gemischten Algen (Chlorella
`vulgaris und Scenedesmus acutus) auf die Lebenstafel-Demographie
`von Brachionus calycifiorus und Brachionus patulus (Rotifera: Brachio-
`nidae)
`
`© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
`
`3
`
`

`

`A. Riethmiiller, E. Langer
`
`622
`
`Saisonales Vorkommen von Arten der Saprolegniales und Leptomitales
`im Auesee und in der Fulda in Kassel (Hessen) unter Beriicksichtigung
`fischpathogener Arten
`
`Seasonal Occurrence of Species of Saprolegniales and Leptomitales in
`Lake Aue andthe River Fulda in Kassel (Hesse) with Special Considera-
`tion of Fish Pathogenic Species
`
`635 Theses in Water Sciences
`
`637. Meetings
`
`638 New Publications
`
`640 Recent Contents
`
`© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
`
`www.wiley-vch.de/home/actahydro
`
`4
`
`

`

`Acta hydrochim. hydrobiol. 33 (2005) 6, 579-584
`
`DOI 10.1002/aheh.200400600
`
`979
`
`Marcus ClauB?,
`Rolf Mannesmann®,
`Andreas Kolch®
`
`® Faculty of Biology,
`University of Bielefeld,
`33615 Bielefeld, Germany
`® WEDECO AG Water
`Technologies,
`Boschstr. 6, 32051 Herford,
`Germany
`
`Photoreactivation of Escherichia coli and
`Yersinia enterolytica after Irradiation with a
`222 nm Excimer Lamp Comparedto a 254 nm
`Low-pressure Mercury Lamp
`
`Photoreactivation of Escherichia coli ATCC 11229 and Yersinia enterolytica ATCC 4780
`after irradiation with a 222 nm krypton-chloride excimer lamp compared to a 254 nm mer-
`cury lamp was investigated under laboratory conditions. The bacteria samples were
`irradiated each with different doses of both wavelengths.After irradiation one sample of
`the bacteria wasilluminated with fluorescentlight, the other sample was stored in darkness
`to prevent photoreactivation. The inactivation curves were determined. Without photoreac-
`tivation, an irradiation of 69 J/m* at 254 nm wassufficient for a 4 log reduction for E. coli,
`and only 59 J/m? for Y. enterolytica. To get a 4 log reduction with following photoreacti-
`vation, 182 J/m? were necessary for E. coli and 180 J/m?for Y. enterolytica. Afterirradiation
`with the 222 nm excimer lamp the ratios were different. Without photoreactivation, an
`irradiation of 106 J/m? at 222 nm was sufficient for a 4 log reduction for E. coli and
`88 J/m? for Y. enterolytica. With photoreactivation 161 J/m? were necessary for E. coli to
`get a 4 log reduction and 117 J/m? for Y. enterolytica.
`Whenthe photoreactivation after irradiation is excluded, the mercury lamp with 254 nm
`clearly showsbetter results regarding inactivation. Whereas, when included, the excimer
`lamp with 222 nm wavelength obviously showsbetter results.
`
`
`Photoreaktivierung von Escherichia coli und Yersinia enterolytica nach Bestrahlung
`mit einem 222 nm-Excimerstrahler im Vergleich mit einem 254 nm-Niederdruck-
`Quecksilberstrahler
`
`Die Photoreaktivierung von Escherichia coli ATCC 11229 und Yersinia enterolytica ATCC
`4780 nach Bestrahlung mit einem 222 nm-Krypton-Chlorid-Excimerstrahler im Vergleich
`zu einem 254 nm-Niederdruck-Quecksilberstrahler wurde unter Laborbedingungen unter-
`sucht. Proben beider Bakterienarten wurden mit verschiedenen Dosen beider Wellen-
`
`langen bestrahit. Danach wurde zur Photoreaktivierung eine Probe Fluoreszenzlicht aus-
`gesetzt, die andere dunkel gehalten, um diese zu verhindern. Dann wurden die Inaktivie-
`rungskurven ermittelt. Bei der Bestrahlung mit dem 254 nm-Quecksilber-Niederdruck-
`Strahler waren ohne anschlieBende Photoreaktivierung fir eine Inaktivierung von 4 log-
`Stufen 69 J/m? fir E. coli und 59 J/m?fiir ¥. enterolytica nétig. Mit anschlieBender Photo-
`reaktivierung waren es dagegen 182 J/m?fiir E. colf und 180 J/m? fiir ¥. enterolytica. Bei
`Bestrahlung mit dem 222 nm-Excimerstrahler zeigen sich deutliche Unterschiede bei den
`Verhaltnissen. Ohne anschlieBende Photoreaktivierung war hier flr eine Reduktion von
`4 log-Stufen eine Bestrahlung von 106 J/m? fur E. coli und 88 J/m? fir Y. enterolytica
`nétig. Mit Photoreaktivierung waren es 161 J/m? fiir E. coli und 117 J/m? fur Y. enterolytica.
`Wird die Photoreaktivierung ausgeschlossen, zeigt der Quecksilberstrahler bessere
`Ergebnisse bei der Inaktivierung, mit anschlieBender Photoreaktivierung jedoch der
`Excimerstrahler.
`
`Keywords: Ultraviolet Radiation, Water Disinfection, Photolyase, Proteins
`
`Schlagw6rter: Ultraviolette Strahlung, Wasserdesinfektion, Photolyase, Proteine
`
`ResearchPaper
`pomneeeaes
`
`
`
`Correspondence: M. ClauB, E-mail: marcus.clauss @ uni-bielefeld.de
`
`re‘© InterScience®
`
`
`DiscOvis POUETHING GREAT
`
`© 2005 WILEY-VCH Verlag GmbH & Co, KGaA, Weinheim
`
`5
`
`5
`
`

`

`580 M. Clauf etal.
`
`1 Introduction
`
`Low-pressure mercury lampsaretraditionally used for water
`disinfection. Their nearly monochromatic emission of
`254 nm almost corresponds with the maximum of DNA ab-
`sorption at approx. 260 nm. This absorption causes damage
`to DNA byaltering nucleotide base paring, especially 6—4
`photoproducts and thymine dimers formation [1, 2].
`If the
`damage remains unrepaired, DNA transcription and repli-
`cation is blocked. This finally leads to cell death.
`
`There are also other targets in the cell which are damaged
`by UV radiation by different wavelengths. Damage of mem-
`branes has been reported to occur in cells of Escherichia
`coli only after irradiation with UV radiation above 305 nm [3].
`In contrastto this, membranes of Saccharomyces cerevisiae
`yeast cells were damaged byradiation at wavelengths less
`than 200 nm only [4]. This membrane damage is predomi-
`nantly caused by UV radiation formed radicals which react
`to escharotic lipoperoxides in the unsaturated fatty acids of
`the membrane [5]. Much more important seems to be the
`damage done to aminoacids, and thusalsoin proteins com-
`posedoutof it. Out of the 20 most common amino acids
`only phenylalanin, tyrosin, tryptophan, cystein, cystin [6] and
`histidin [7] show a peak UV absorption in the area of
`280 nm and a higher one at 220 nm. At wavelengths ex-
`ceeding 200 nm the absorption spectra of proteins and those
`of the composition of their constituents are comparable [6,
`8]. Thus, proteins also show absorption maxima at 220 nm
`and 280 nm.
`
`Both prokaryotic and eukaryotic cells have special mecha-
`nisms to remove DNAdefects [1]. Among the nucleotide ex-
`cision repair (NER), also known as dark repair, one of the
`most important repair mechanisms is the photoreactivation
`[9]. This process has been well researched and uses a
`single enzyme called photolyase to repair UV-induced dam-
`age in the DNA [10-12]. The photolyase of E. coli is basi-
`cally specific for repair of pyrimidine dimer. It catalyses the
`reaction from cis-syn pyrimidin dimers to the original pyrimi-
`din monomers in DNA.It is a light-dependent process which
`requires specific wavelengths ranging from 300...500 nm
`and is much more effective and faster than the NER [9]. This
`leads to problems when treated water is exposed to light
`and microorganisms which obviously have already been in-
`activated begin to reactivate,
`for example in UV-treated
`wastewater after
`its discharge to runoff ditches. One
`possible solution being applied in practice is to increase the
`irradiance to such a high value that the DNAis extensively
`damaged and photoreactivation is no longer possible. How-
`ever, the higher power consumptionis still a disadvantage.
`Due to the fact that the photoreactivation only repairs DNA
`damageit would beinteresting to investigate the photoreac-
`tivation of bacteria after irradiation with wavelengths in the
`range of the absorption maximaofproteins.
`
`Acta hydrochim. hydrobiol. 33 (2005) 6, 579-584
`
`Several authors investigated the use of other types of UV
`lamps for water disinfection like medium-pressure mercury
`lamps with a broader emission spectrum from far UVto infra-
`red [13—15] excimer lamps [16, 17] and excimer laser[18].
`But special reactivation studies in the past only focused on
`DNArepair of microorganisms following UV-exposure from
`low-pressure [19, 20] and medium-pressure lamps [13-15].
`The broad emission spectrum of a medium-pressure lamp
`indeed contains wavelengthsalso in the range of the absorp-
`tion maximaofproteins,butit is rather unspecific. In contrast
`to this a krypton-chloride excimer lamp showsa relatively
`sharp emission spectrum with a peak at 222 nm (Fig. 1).
`
`The intention of the following experiment was to compare
`the photoreactivation of Escherichia coli and Yersinia enter-
`olytica after irradiation with a 222 nm (near protein absorp-
`tion max.) excimer Jamp with a 254 nm (near DNA absorp-
`tion max.) low-pressure mercury lamp underlaboratory con-
`ditions. The bacteria wereirradiated with the UV radiation
`
`from the two lamps. Afterwards the suspension wasillumi-
`nated with fluorescent light. Then the reduction of the colony
`forming units was investigated after different
`irradiation
`times with and without photoreactivation.
`
`2 Materials and methods
`
`UV source.A collimated beam device (WEDECO AG Water
`Technology) was used forirradiation corresponding to the
`details of the DVGW-guideline W 294 [21]. This device con-
`tains interchangeable lamp units. One lamp unit is equipped
`with four low-pressure mercury lamps, type NLR 2036; the
`other unit is equipped with two KrCl-excimer lamps. The dis-
`tance betweenthe probes and the UV lamps was 51 cm. For
`both units the emission spectrum and the irradiance were
`measured with a Bentham Spectrometer DM 150 Double
`Monochromator with a 200...450 nm standard sensing head.
`The real power consumption taken from the main supply
`was 185 W for the mercury lamp and 86 W for the excimer
`lamp.
`
`Figure 1 shows the measured irradiance of both lamps
`plotted logarithmically against
`the wavelength. The ir-
`radiance of the mercury lamp in the whole UV region
`(200...380 nm) is 22.10 W/m? and therefore much higher
`than that of the excimer lamp with 3.55 W/m. In the UV-C
`region (200...280 nm) the irradiances are 20.95 W/m? and
`3.38 Wim?.
`
`Photoreactivation. The inactivation was followed by expo-
`sure to fluorescent lamps. For the photoreactivation the
`probes wereilluminated with four (7 cm horizontally apart)
`fluorescent tube lamps (Osram Biolux 18 W, 600 mm length;
`daylight spectrum from 360...700 nm). To ensure that the
`light intensity in the Petri dishes was even, the illuminations
`
`© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
`
`www.wiley-vch.de/home/actahydro
`
`6
`
`

`

`Photoreactivation of Bacteria at 222 nm 581
`
`the DVGW [21] and the
`cording to the regulations of
`ONORM[22], which lay down the requirements and testing
`of plants for the disinfection of water using ultraviolet radi-
`ation. Each time 25 mL of test suspension were irradiated
`for different periods of times (depending on the lamps and
`the microorganisms to be irradiated) in 85 mm standard
`polystyrene Petri dishes (arithmetical thickness of 4.4 mm)
`without intermixing. In order to determine the exact inacti-
`vation kinetic, five duplicate samples of each of the microor-
`ganisms wereirradiated. After irradiation one sample of the
`bacteria was illuminated with fluorescent
`light,
`the other
`sample wasstored in darkness to prevent photoreactivation.
`To set a decimaldilution series after irradiation 1 mL of the
`
`test suspension was taken from the centre of the Petri dish
`each time. 100 pL of the dilutions were plated 3 x for the
`dilution steps 10-2 to 107° in pour-plate method with PC-
`Agar: Tryptone (Oxoid LP0042) 5.0 g, yeast extract (Oxoid
`LP0021) 2.5 g, glucose (Oxoid LP0071) 1.0 g and agar
`(Oxoid LP0011) 10.0 g in 1 L distilled water. For the dilution
`steps 10° and 10-1, 1 mL and 100 pLof the test suspension
`were taken from the centre of the Petri dish and directly
`plated. The following incubation of the microbes was done
`at 37°C in a darkenedincubator for 24 hours. For the arith-
`
`metical evaluation of the results three agar plates each of
`this dilution step with 10...300 colonies were used. These
`were counted and the results arithmetically averaged. The
`mean was then divided by the corresponding dilution step
`and the commonlogarithm was calculated. From these five
`Ig concentrations the average value wascalculated. The cor-
`responding reduction for the respective irradiation time is
`calculated by Ig(M/No). This dose reduction factor was plot-
`ted logarithmically as function of the irradiance.
`
`3 Results
`
`The UV inactivation results for E. coliand Y. enterolytica are
`presented in Figures 2 and 3. They show onlyslight differ-
`encesin the UV sensitivity of the two bacteria species. The
`UV irradiation/reduction response curves of E. coli and
`Y. enterolytica without photoreactivation developed in this
`study differ from the curves with photoreactivation.
`
`Without photoreactivation, an irradiation of 69 J/m? at
`254 nm was sufficient for a 4 log reduction for E. coli, and
`only 59 J/m? for Y. enterolytica.
`In contrast, the same ir-
`radiation with following photoreactivation showed an approx.
`0.5 log reduction only for E. coli and 0.7 for ¥. enterolytica.
`To get a 4 log reduction after irradiation and following
`photoreactivation, 182 J/m* were necessary for E. coli and
`180 J/m? for Y. enterolytica.
`
`After irradiation with the 222 nm excimer lamp the ratios
`were different compared to the 254 nm mercury lamp. With-
`out photoreactivation, an irradiation of 106 J/m? at 222 nm
`
`:
`=
`
`£ 8#
`
`e
`
`Wavelength in nm
`
`Fig. 1: Emission spectra of the 254 nm mercury lamp and
`the 222 nm KrCl-excimer lamp from 200...400 nm wave-
`length.
`
`Emissionsspektren des 254 nm-Quecksilber-Niederdruck-
`strahlers und des 222 nm-Krypton-Chlorid-Excimerstrahlers
`im Wellenlangenbereich 200...400 nm.
`
`were done in a box (62 cm | X 50 cm h X 32 cm w)lined
`with aluminium foil to reflect scattered light and to exclude
`light from outside.
`
`Organismsand their cultivation. Culture: Escherichia coli
`ATCC 11229 and Yersinia enterolytica ATCC 4780 (Amer-
`ican Type Culture Collection, Manassas, VA). Incubation of
`E. colifor 14 h in Endo’s broth: Meat extract (Merck 103979)
`3.0 g and tryptone (Oxoid LP0042) 2.5 g perlitre aqua de-
`min. Incubation of Y. enterolytica for 14 h in Caso’s broth:
`Tryptone (Oxoid LP0042) 15.0 g, peptone from soymeal
`(Oxoid LP0044) 5.0 g, NaCl (Oxoid LP0005) 5.0 g perlitre
`aqua demin. Bacteria were harvested by centrifugation (Bio-
`fuge 28 RS, company Heraeus) with 2600 upm for 10 min
`at 20°C, the pellet was resuspended in 100 mL 0.65% NaCl
`and filtrated through a 5.0 ym filter (Cellulose-Nitrate-Filter,
`Sartorius).
`
`Standardization of bacteria titer. For irradiation the titer of
`the test suspension was standardized at 1 - 10° bacteria/mL
`as follows: The extinctions of the respective bacteria sus-
`pension were measured at 510 nm in a 5 cm quartz glass
`cuvette against a 0.65% NaCl solution in a photometer
`(Hitachi U-1100 Spectrometer) and then further diluted with
`the solution until an extinction of 0.100 was reached. To this
`extinction the respective titer was determined. Then, the
`numberof organisms/mL to 1
`- 10° could be adjusted by
`diluting the corresponding stock suspension.
`
`irradiation and evaluation of the results. The irradiation
`
`and the consequent evaluation of the results were done ac-
`
`© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
`
`www.wiley-vch.de/home/actahydro
`
`Acta hydrochim. hydrobiol. 33 (2005) 6, 579-584
`100
`
`40
`
`;
`
`——— low-pressure
`mercury lamp
`— krypton chloride
`excimer lamp
`
`
`0,1
`
`0,01
`
`0,001
`
`7
`
`

`

`582 M. Clauf etal.
`
`Acta hydrochim. hydrobiol. 33 (2005) 6, 579-584
`
`Escherichia coli
`
`4 222 nm
`~]& 222 nm+pr
`Oo 254m
`
`“| 254 nm+tp:
`
`Ig(N/No)
`DoseReductionFactor
`
`
`
`0
`
`40
`
`80
`
`120
`
`160
`
`200
`
`Yersinia enterolytica
`
`Ig(N/No)
`DoseReductionFactor
`
`
`
`0
`
`40
`
`80
`
`120
`
`160
`
`200
`
`Irradiation in J/m?
`
`Irradiation in J/m?
`
`Fig. 2: Inactivation curves for E. colf ATCC 11229 afterirradi-
`ation with a 222 nm KrCl excimer famp and a 254 nm low-
`pressure mercury lamp with and without photoreactivation
`(pr) afterwards. All symbols indicate the mean offive inde-
`pendentseries of experiments. Error bars denote the highest
`and lowest value.
`
`Fig. 3: Inactivation curves for ¥. enterolytica ATCC 4780
`after irradiation with a 222 nm KrCl excimer lamp and a
`254 nm low-pressure mercury lamp with and without photo-
`reactivation (pr) afterwards. All symbols indicate the results
`of five independentseries of experiments. Error bars denote
`the highest and lowestvalue.
`
`Inaktivierungskurven fir E. coli ATCC 11229 nach Bestrah-
`lung mit einem 222 nm-Krypton-Chlorid-Excimerstrahler und
`einem 254 nm-Quecksilber-Niederdruckstrahler mit und
`
`Inaktivierungskurvenfir Y. enterolytica ATCC 4780 nach Be-
`strahlung mit einem 222 nm-Krypton-Chlorid-Excimerstrah-
`ler und einem 254 nm-Quecksilber-Niederdruckstrahler mit
`
`ohne anschlieBende Photoreaktivierung (pr). Die Symbole
`stehen fir den Mittelwert aus flinf unabhangigen Versuchs-
`reihen. Die Fehlerbalken zeigen den héchsten und den nied-
`rigsten Wert an.
`
`und ohne anschlieBende Photoreaktivierung (pr). Die Sym-
`bole stehen fiir den Mittelwert aus finf unabhangigen Ver-
`suchsreihen. Die Fehlerbalken zeigen den héchsterm und
`den niedrigsten Wert an.
`
`wassufficient for E. coli for a 4 log reduction. However, the
`same irradiation with following photoreactivation still showed
`a 1.4 log reduction. In this case only 161 J/m? were neces-
`sary for E. coli to get a 4 log reduction. Also Y. enterolytica
`showed similar results. Without photoreactivation, an ir-
`radiation of 88 J/m* at 222 nm wassufficient for a 4 log
`reduction. In contrast, the sameirradiation with photoreacti-
`vation showed an approx. 2.3 log reduction.
`In this case
`117 J/m? were necessary to get a 4 log reduction.
`
`Whenthe photoreactivation after irradiation is excluded, the
`mercury lamp with 254 nm clearly shows better results re-
`garding inactivation. Whereas, on the other hand with photo-
`reactivation afterwards the excimer lamp with 222 nm wave-
`length obviously showsbetter results.
`
`4 Discussion
`
`Photolyase activity and the resulting photoreactivation were
`found in many prokariotic and eukaryotic organisms [9].
`E. coli was selected for this study becauseit is commonly
`used as a biological indicator of disinfection efficiency in
`water systems. Its dark- and photorepair processesfollowing
`exposure to UV radiation are well known and have been ex-
`
`tensively studied. This strain was specifically chosen be-
`cause it is known to undergo photorepair folldwing low-
`pressure UV exposure up to a dose of 280 J/m* [20].
`Y. enterolytica is not a commontest organism but similar to
`E. coli, it has a highly-efficient photorepair mechanism for
`UV radiation induced damage at 254 nm andis actually able
`to undergo photorepair up to 320 J/m? [20].
`
`The bacterial low-pressure UV irradiation/survival response
`curves developedin this study are similar to other published
`curvesfor these bacteria [12, 17, 23, 24]. Also values for 3
`or 4 log reductions are similar. After a 4 log reduction of the
`colony count
`(10°/mL—10?/mL)
`trough UV rays,
`tHe re-
`duction rate could be decreased to only 1 log (10°/mL)after
`UV disinfection and photoreactivation [19]. The sameratio
`wasinvestigatedin this study. But sometimes the valuesdif-
`fer from some authors; however, the ratios are similar. For
`example, an irradiation for a 4 log reduction without photore-
`activation was given for E. coli ATCC 11229 and Y. enteroly-
`tica (no strain was given), each with 100 J/m?[20] (in this
`study 69 J/m?for E. coli and 59 J/m? for Y. enterolytica). For
`the same reduction with photoreactivation 280.J/m? for
`E. coli and 320 J/m? for Y. enterolytica were necessary
`(182 J/m? and 180 J/m?in this study).It is commonly known
`that results regarding the inactivation of bacteria which can
`
`© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
`
`www.wiley-vch.de/home/actahydro
`
`8
`
`

`

`Acta hydrochim. hydrobiol. 33 (2005) 6, 579-584
`
`Photoreactivation of Bacteria at 222 nm 583
`
`assumed that protein damage is most probable [6-8],
`whereasother authors supposethatthis is due to the fact
`that repair of photodimers and 6-4 photoproducts is better
`than the one of damage induced due to photoionization at
`lower wavelength [18]. Another possibility is,
`that wave-
`length of 220...300 nm reduced the subsequent photorepair,
`possibly by causing a disorder in endogenous photolyase,
`the enzymespecific for photoreactivation [25].
`
`With 3.38 W/m? measured in the UV-C region the excimer
`lamp has a muchlower irradiance than the mercury lamp
`with 20.95 W/m?(Fig. 1), but the real power, actually taken
`from the main supply, is with 185 W for the mercury lamp
`2.1 times higher than for the excimer lamp with 86.6 W. With
`regard to electric energy consumed andthe resulting inacti-
`vation the mercury lamp is more efficient when photoreacti-
`vation is excluded. Whereas, when included, the excimer
`lamp with 222 nm wavelength is moreefficient.
`
`It should be pointed out that photons at the higher wave-
`length of 254 nm have a deeperpenetration in water than
`222 nm photons (for example 172 nm only approx. 30 pm,
`222 nm approx. 3 cm [16]). If the transmission of 1 cm water
`at 254 nm is set as 100%, the transmission at 222 nm is
`97.3%, but the thickness of the suspensions which wereir-
`radiated in this study was less than 0.5 mm.
`
`Acknowledgements
`
`This work was supported by the company WEDECO AG,
`Herford. Special thanks go to the Radium Lampenwerk
`GmbHfor the supply of the KrC! excimer lamp.
`
`References
`
`{1] Kiefer, J.: Ultraviolette Strahlen. Walter de Gruyter, Berlin,
`1977.
`
`[3=
`
`[5—
`
`[2] Matsunga, T., Hieda, K., Nikaido, O.: Wavelength depen-
`dent formation of thymine dimers and (6—4) photoproducts
`in DNA by monochromatic ultraviolet
`light ranging from
`150-365 nm. Photochem. Photobiol. 54, 403—410 (1991).
`Kelland, L. R., Moss, S. H., Davies, D. J. G.. Leakage of
`®6Rb* after ultraviolet irradiation of E. coli K-12. Photo-
`300% moreto obtain the same reduction as without photore-
`activation. At 222 nmahigher irradiation of only 25% for
`chem. Photobiol. 39, 329-335 (1984).
`E. coli and 50%for Y. enterolytica are necessary to get the
`[4] Hieda, K.,
`Ito, T: Action spectra for
`inactivation and
`same inactivation as without photoreactivation.
`membrane damage of Saccharomyces cerevisiae cells
`irradiated in vakuum by monochromatic synchroton UV-
`radiation (155-250 nm). Photochem. Photobiol. 44,
`409-411 (1986).
`Beier, W.: Erzeugung, Messung und Anwendung ultra-
`violetter Strahlen. In: Fortschritte der experimentellen und
`theoretischen Biophysik. 25, VEB Georg Thieme, Leipzig,
`1980.
`
`be foundin literature are contradictory, due to the different
`experimental conditions and the large variability of the bac-
`teria.
`
`No bacterial UV irradiation/survival response curve for the
`irradiation with a 222 nm excimer lamp could be found for
`these bacteria except for E. coli in preliminary investigations
`[17] and only some data in theliterature [16]. In preliminary
`investigations it was found that under laboratory conditions
`the requiredirradiation for a 4 log reduction of E. coli ATCC
`25922is 60 J/m? with 254 nm UV radiation and 86 J/m? with
`222 nm UVradiation [17]. At least the ratio is very similar to
`69 J/m? for 254 nm and 106 J/m? for 222 nm foundin this
`investigation. A 0.4 log reduction of E. coli as found in litera-
`ture, irradiated with a 222 nm KrCl excimer lamp in a flowing
`system compared to a more than 4 log reduction under the
`same conditions with a 254 nm low-pressure UV lamp [16].
`This reduction correlates with the one investigated in this
`study.
`
`Also no data for photoreactivation at 222 nm could be found
`in literature. Nevertheless, clues are given in some papers
`that deal with the photoreactivation afterirradiation with low-
`and medium-pressure UV sources [14, 15, 25]. The general
`conclusion in these papers is that the survival ratio of the
`bacteria after photoreactivation following medium-pressure
`lamps is smaller than that of low-pressure lamps. The emis-
`sion spectrum of medium-pressure mercury lamps contains
`also wavelengths of around 222 nm.
`It could thus be as-
`sumedthat this effect also occurs here.
`
`In general, it is recognizable that without photoreactivation
`the inactivation with UV radiation with 254 nm wavelength
`near the absorption maxima of DNAis mosteffective, and
`DNAhas always been regarded as the mostimportant target
`molecule for UV radiation. To get the same inactivation re-
`sults with 222 nm wavelength the necessary irradiation has
`to be 50% higher. This is according to preliminary results for
`irradiated E. coli, Enterococcus faecalis and Candida al-
`bicans, which were inactivated 1.5 times better with 254 nm
`than with 222 nm [17]. But when the bacteria get the chance
`to photoreactivate, the ratios change. With photoreactivation
`andirradiation with 254 nm the bacteria hasto beirradiated
`
`In summary, the photoreactivation has a lower level after ir-
`radiation with 222 nm wavelength compared to 254 nm.
`These results indicate the damage of other molecules at
`222 nm among the DNA, because photoreactivation is a
`DNA repair p