Inactivation and mechanism of UV₂₂₂ radiation on cyanobacteria: Microcystis aeruginosa in aggregates and unicellular forms

Abstract

Cyanobacterial blooms persistently threaten the safety of drinking water. While UV₂₂₂ is highly effective and safe for inactivating microorganisms such as viruses and bacteria, its efficacy against cyanobacteria remains unclear. This study investigated the inactivation effects and mechanisms of UV₂₂₂ on laboratory-prepared Microcystis aeruginosa (M. aeruginosa) aggregates and unicellular cells. The M. aeruginosa aggregates and unicellular cells could be inactivated by a 1–15 mJ/cm² dose of UV₂₂₂, with the inactivation primarily involving damage to the photosystem, cell integrity, and biomacromolecules, along with impaired metabolic functions. The aggregates exhibited greater UV₂₂₂ resistance than that of the unicellular cells, attributable to the outer cell shielding and protective protein components exist in extracellular polymeric substances (EPS). Although UV₂₂₂ impaired the photosynthetic activity and damaged the cell membranes of the aggregates, their regrowth capacity persisted. Conversely, the unicellular cells suffered extreme inhibition of F_v/F_m and esterase activity, with near-complete loss of regrowth ability at UV₂₂₂ doses > 6 mJ/cm². UV₂₂₂ directly damaged the cell membrane, chlorophyll-a, and phycocyanin, reducing cyanobacterial activity. Additionally, M. aeruginosa was more readily inactivated during the late lag phase than during the exponential phase (e.g., membrane damage proportions were 95% vs. 87%, respectively). These findings demonstrate the potential of UV₂₂₂ for cyanobacterial control and highlight the need to consider practical factors such as aggregation morphology, growth-phase differences, and media effects on radiation efficacy in applications.

Graphical abstract

Keywords

Cyanobacterial blooms / Microcystis aeruginosa / Aggregates / UV₂₂₂

Highlight

	● Lab cyanobacterial aggregates morphology and composition were similar to field samples.
	● Inner cells in aggregates could be protected by outer cells from UV222 attacked.
	● Cyanobacterial aggregates were more resistant to UV222 than unicellular cell.
	● UV222 attacked cyanobacterial activities, membrane, biomacromolecule and proteins.
	● Cyanobacterial growth phases would affect UV222 inactivation effect.

References

[1] Battin T J . (1997). Assessment of fluorescein diacetate hydrolysis as a measure of total esterase activity in natural stream sediment biofilms. Science of the Total Environment, 198(1): 51–60

[2] Ben Abdallah F , Lagha R , Ellafi A , Namane A , Rousselle J C , Lenormand P , Kallel H . (2012). Identification of outer membrane proteins altered in response to UVC-radiation in Vibrio parahaemolyticus and Vibrio alginolyticus. Indian Journal of Microbiology, 52(4): 660–665

[3] Bhunia B , Uday U S P , Oinam G , Mondal A , Bandyopadhyay T K , Tiwari O N . (2018). Characterization, genetic regulation and production of cyanobacterial exopolysaccharides and its applicability for heavy metal removal. Carbohydrate Polymers, 179: 228–243

[4] Chang C W , Huo X C , Lin T F . (2018). Exposure of Microcystis aeruginosa to hydrogen peroxide and titanium dioxide under visible light conditions: modeling the impact of hydrogen peroxide and hydroxyl radical on cell rupture and microcystin degradation. Water Research, 141: 217–226

[5] Chen M , Tian L L , Ren C Y , Xu C Y , Wang Y Y , Li L . (2019). Extracellular polysaccharide synthesis in a bloom-forming strain of Microcystis aeruginosa: implications for colonization and buoyancy. Scientific Reports, 9(1): 1251

[6] Cho Y S , Bin Song K , Yamada K , Han G J . (2008). Effect of ultraviolet irradiation on molecular properties of ovalbumin. Journal of the Korean Society for Applied Biological Chemistry, 51(4): 276–280

[7] Choi Y , He H , Dodd M C , Lee Y . (2021). Degradation kinetics of antibiotic resistance gene mecA of methicillin-resistant Staphylococcus aureus (MRSA) during water disinfection with chlorine, ozone, and ultraviolet light. Environmental Science & Technology, 55(4): 2541–2552

[8] Clauß M , Grotjohann N . (2008). Effective photoinactivation of alpha-amylase, catalase and urease at 222 nm emitted by an KrCl-excimer lamp. Clean - Soil, Air, Water, 36(9): 754–759

[9] Das S , Purkayastha P . (2017). Gold nanocluster protection of protein from UVC Radiation: a model study on bovine serum albumin. ACS Omega, 2(6): 2451–2458

[10] Davies B H , Jones D , Goodwin T W . (1963). Studies in carotenogenesis. 30. The problem of lycopersene formation in Neurospora crassa. Biochemical Journal, 87(2): 326–329

[11] de la Fuente A , Muro-Pastor A M , Merchán F , Madrid F , Pérez-Martínez J I , Undabeytia T . (2019). Electrocoagulation/flocculation of cyanobacteria from surface waters. Journal of Cleaner Production, 238: 117964

[12] des Aulnois M G , Réveillon D , Robert E , Caruana A , Briand E , Guljamow A , Dittmann E , Amzil Z , Bormans M . (2020). Salt shock responses of Microcystis revealed through physiological, transcript, and metabolomic analyses. Toxins, 12(3): 192

[13] Duan Z P , Tan X , Zeng Q F . (2022). Key physiological traits and chemical properties of extracellular polymeric substances determining colony formation in a cyanobacterium. Journal of Oceanology and Limnology, 40(5): 1720–1731

[14] Fan J J , Ho L , Hobson P , Brookes J . (2013). Evaluating the effectiveness of copper sulphate, chlorine, potassium permang-anate, hydrogen peroxide and ozone on cyanobacterial cell integrity. Water Research, 47(14): 5153–5164

[15] Fan J J , Rao L , Chiu Y T , Lin T F . (2016). Impact of chlorine on the cell integrity and toxin release and degradation of colonial Microcystis. Water Research, 102: 394–404

[16] Futra D , Heng L Y , Surif S , Ahmad A , Ling T L . (2014). Microencapsulated Aliivibrio fischeri in alginate microspheres for monitoring heavy metal toxicity in environmental waters. Sensors, 14(12): 23248–23268

[17] Gao L , Pan X L , Zhang D Y , Mu S Y , Lee D J , Halik U . (2015). Extracellular polymeric substances buffer against the biocidal effect of H₂O₂ on the bloom-forming cyanobacterium Microcystis aeruginosa. Water Research, 69: 51–58

[18] Gao X , Zheng T , Yuan X L , Dong Y B , Liu C . (2023). Biocidal H₂O₂ treatment emphasizes the crucial role of cyanobacterial extracellular polysaccharides against external strong oxidative stress. Environmental Science and Pollution Research, 30(21): 60654–60662

[19] Ge Z Y , Chen X G , Fan J J . (2025). Efficient removal of harmful algae from eutrophic natural water by Mg(OH)₂ coated nanoscale zero-valent iron. Frontiers of Environmental Science & Engineering, 19(4): 55

[20] Gong Y P , Chen H H , Li W X , Zhou C P , Zhou R G , Zhao H M , Shao H F . (2022). Gradient printing alginate herero gel microspheres for three-dimensional cell culture. Materials, 15(6): 2305

[21] Henderson R K , Baker A , Parsons S A , Jefferson B . (2008). Characterisation of algogenic organic matter extracted from cyanobacteria, green algae and diatoms. Water Research, 42(13): 3435–3445

[22] Hu C Y , Hu L L , Zhang T Y , Yang X Y , Liu H , Chen J N , Gao L M , Dong Z Y . (2025). Far-UVC direct photolysis of iohexol and acetochlor: an experimental and mechanism study. Environ-mental Technology, 46(13): 2429–2439

[23] Huang R , Liu Z Q , Yan B Y , Zhang J L , Liu D M , Xu Y P , Wang P , Cui F Y , Liu Z Q . (2019). Formation kinetics of disinfection byproducts in algal-laden water during chlorination: a new insight into evaluating disinfection formation risk. Environmental Pollution, 245: 63–70

[24] Jeffrey S W . (1968). Quantitative thin-layer chromatography of chlorophylls and carotenoids from marine algae. Biochimica et Biophysica Acta (BBA)– Bioenergetics, 162(2): 271–285

[25] Ji X Y , Jiang M Q , Zhang J B , Jiang X Y , Zheng Z . (2018). The interactions of algae-bacteria symbiotic system and its effects on nutrients removal from synthetic wastewater. Bioresource Technology, 247: 44–50

[26] Jing Z B, Lu Z D, Santoro D, Zhao Z N, Huang Y, Ke Y C, Wang X H, Sun W J (2022). Which UV wavelength is the most effective for chlorine-resistant bacteria in terms of the impact of activity, cell membrane and DNA? Chemical Engineering Journal, 447: 137584

[27] Kang J W , Kim S S , Kang D H . (2018). Inactivation dynamics of 222 nm krypton-chlorine excilamp irradiation on Gram-positive and Gram-negative foodborne pathogenic bacteria. Food Research International, 109: 325–333

[28] Li S , Tao Y , Zhan X M , Dao G H , Hu H Y . (2020). UV-C irradiation for harmful algal blooms control: a literature review on effectiveness, mechanisms, influencing factors and facilities. Science of the Total Environment, 723: 137986

[29] Li T , Zhang Y Z , Gan J M , Yu X , Wang L . (2023). Superiority of UV222 radiation by in situ aquatic electrode KrCl excimer in disinfecting waterborne pathogens: mechanism and efficacy. Journal of Hazardous Materials, 452: 131292

[30] Li X , Zeng J , Yu X . (2021). Different response pattern of cyano-bacteria at development and maintenance stage to potassium permanganate oxidation. Journal of Hazardous Materials, 419: 126492

[31] Liang Z W , Li W H , Yang S Y , Du P . (2010). Extraction and structural characteristics of extracellular polymeric substances (EPS), pellets in autotrophic nitrifying biofilm and activated sludge. Chemosphere, 81(5): 626–632

[32] Lin P P , Li Y D , Zhao M , Rosado-García F M , Zheng B X , Peña Y P , Wang L . (2025). Comparison of E. coli inactivation by UV₂₂₂-ADPs and UV₂₅₄-ADPs in water. Frontiers of Environmental Science & Engineering, 19(5): 60

[33] Liu L Z , Huang Q , Qin B Q . (2018). Characteristics and roles of Microcystis extracellular polymeric substances (EPS) in cyanobacterial blooms: a short review. Journal of Freshwater Ecology, 33(1): 183–193

[34] Liu X Y , Wang Y H , Liang Z W , Lian X J , Huang D , Hu Y C . (2023). Progress in preparation and application of sodium alginate microspheres. Journal of Biomedical Engineering, 40(4): 792–798

[35] Luo C , Chen C L , Xian X X , Cai W F , Yu X , Ye C S . (2024). The secondary outbreak risk and mechanisms of Microcystis aeruginosa after H₂O₂ treatment. Journal of Hazardous Materials, 470: 134196

[36] Ma B , Seyedi S , Wells E , McCarthy D , Crosbie N , Linden K G . (2022). Inactivation of biofilm-bound bacterial cells using irradiation across UVC wavelengths. Water Research, 217: 118379

[37] Ma MLiu R PLiu H JQu J H (2012). Chlorination of Microcystis aeruginosa suspension: cell lysis, toxin release and degradation. Journal of Hazardous Materials, 217–218: 217–218

[38] Matafonova G G , Batoev V B , Astakhova S A , Gómez M , Christofi N . (2008). Efficiency of KrCl excilamp (222 nm) for inactivation of bacteria in suspension. Letters in Applied Microbiology, 47(6): 508–513

[39] Naceradska J , Pivokonsky M , Pivokonska L , Baresova M , Henderson R K , Zamyadi A , Janda V . (2017). The impact of pre-oxidation with potassium permanganate on cyanobacterial organic matter removal by coagulation. Water Research, 114: 42–49

[40] Ni L X , Yue F F , Zhang J H , Rong S Y , Liu X Y , Wang Y F , Wang P F , Li D Y , Wang N , Wu H Q . et al. (2020). Cell membrane damage induced by continuous stress of artemisinin sustained-release microspheres (ASMs) on Microcystis aeruginosa at different physiological stages. Environmental Science and Pollution Research, 27(11): 12624–12634

[41] O’Neil J M , Davis T W , Burford M A , Gobler C J . (2012). The rise of harmful cyanobacteria blooms: the potential roles of eutrophication and climate change. Harmful Algae, 14: 313–334

[42] Oh C , Sun P P , Araud E , Nguyen T H . (2020). Mechanism and efficacy of virus inactivation by a microplasma UV lamp generating monochromatic UV irradiation at 222 nm. Water Research, 186: 116386

[43] Ou H , Gao N Y , Deng Y , Qiao J L , Wang H . (2012). Immediate and long-term impacts of UV-C irradiation on photosynthetic capacity, survival and microcystin-LR release risk of Microcystis aeruginosa. Water Research, 46(4): 1241–1250

[44] Pattison D IDavies M J (2006). Actions of ultraviolet light on cellular structures. In: Bignold L P, ed. Cancer: Cell Structures, Carcinogens and Genomic Instability. Basel: Birkhäuser, 131–157

[45] Raeiszadeh M , Adeli B . (2020). A critical review on ultraviolet disinfection systems against COVID-19 outbreak: applicability, validation, and safety considerations. ACS Photonics, 7(11): 2941–2951

[46] Raeiszadeh M , Taghipour F . (2021). Inactivation of microorganisms by newly emerged microplasma UV lamps. Chemical Engineering Journal, 413: 127490

[47] Reignier O , Bormans M , Marchand L , Sinquin C , Amzil Z , Zykwinska A , Briand E . (2023). Production and composition of extracellular polymeric substances by a unicellular strain and natural colonies of Microcystis: impact of salinity and nutrient stress. Environmental Microbiology Reports, 15(6): 783–796

[48] Réveillon D , des Aulnois M G , Savar V , Robert E , Caruana A M N , Briand E , Bormans M . (2024). Extraction and analysis by liquid chromatography-tandem mass spectrometry of intra- and extracellular microcystins and nodularin to study the fate of cyanobacteria and cyanotoxins across the freshwater-marine continuum. Toxicon, 237: 107551

[49] Sheng G P , Yu H Q , Li X Y . (2010). Extracellular polymeric substances (EPS) of microbial aggregates in biological waste-water treatment systems: a review. Biotechnology Advances, 28(6): 882–894

[50] Tang Z Q , Li W , Zhou J , Yu H Y , Huang L , Yan M G , Gu J S , Wei X W . (2009). Antifouling characteristics of sugar immobilized polypropylene microporous membrane by activated sludge and bovine serum albumin. Separation and Purification Technology, 64(3): 332–336

[51] Tao Y , Zhang X H , Au D W T , Mao X Z , Yuan K . (2010). The effects of sub-lethal UV-C irradiation on growth and cell integrity of cyanobacteria and green algae. Chemosphere, 78(5): 541–547

[52] Tran H D M , Boivin S , Kodamatani H , Ikehata K , Fujioka T . (2022). Potential of UV-B and UV-C irradiation in disinfecting microorganisms and removing N-nitrosodimethylamine and 1,4-dioxane for potable water reuse: a review. Chemosphere, 286(2): 137682

[53] Tsenter I , Garkusheva N , Matafonova G , Batoev V . (2022). A novel water disinfection method based on dual-wavelength UV radiation of KrCl (222 nm) and XeBr (282 nm) excilamps. Journal of Environmental Chemical Engineering, 10(3): 107537

[54] Visser P M , Verspagen J M H , Sandrini G , Stal L J , Matthijs H C P , Davis T W , Paerl H W , Huisman J . (2016). How rising CO₂ and global warming may stimulate harmful cyanobacterial blooms. Harmful Algae, 54: 145–159

[55] Wang D , Oppenländer T , El-Din M G , Bolton J R . (2010). Comparison of the disinfection effects of vacuum-UV (VUV) and UV light on Bacillus subtilis spores in aqueous suspensions at 172, 222 and 254 nm. Photochemistry and Photobiology, 86(1): 176–181

[56] Wang Q , Pang W J , Mao Y D , Ge S J , Yu H G , Dai C J , Zhao M . (2020). Changes of extracellular polymeric substance (EPS) during microcystis aeruginosa blooms at different levels of nutrients in a eutrophic microcosmic simulation device. Polish Journal of Environmental Studies, 29(1): 349–360

[57] Wang Y , Li S S , Li J H , Deng J , Pan C , Li P F . (2011). Physiological response of Microcystis to solar UV radiation. Acta Ecologica Sinica, 31(21): 6532–6539

[58] Wang Y G , Yang G R , Ma X Q , Leng F F , Ma J Z , Wang X L . (2017). Study on interaction between coomassie brilliant blue G-250 and bovine serum albumin by fluorescence spectroscopy and molecular modeling. Spectroscopy and Spectral Analysis, 37(8): 2474–2479

[59] Watson S B , Monis P , Baker P , Giglio S . (2016). Biochemistry and genetics of taste- and odor-producing cyanobacteria. Harmful Algae, 54: 112–127

[60] Welch D , Buonanno M , Grilj V , Shuryak I , Crickmore C , Bigelow A W , Randers-Pehrson G , Johnson G W , Brenner D J . (2021). Author correction: far-UVC light: a new tool to control the spread of airborne-mediated microbial diseases. Scientific Reports, 11(1): 18122

[61] Wu T , Yu X , Hu A T , Zhang L , Jin Y , Abid M . (2015). Ultrasonic disruption of yeast cells: underlying mechanism and effects of processing parameters. Innovative Food Science & Emerging Technologies, 28: 59–65

[62] Xian X X , Li X , Ye C S , Wan K , Feng M B , Luo C , Yu X . (2022). Higher sensitivity to Cu²⁺ exposure of Microcystis aeruginosa in late lag phase is beneficial to its control. Water Research, 214: 118207

[63] Xian X X , Wei Y T , Li J J , Luo C , Chen C L , Zhang Q , Li X , Yu X . (2023). Chlorination for Microcystis aeruginosa in the late lag phase: higher inactivation efficiency and lower environmental risk. ACS ES&T Water, 3(2): 448–456

[64] Xiao M , Li M , Reynolds C S . (2018). Colony formation in the cyanobacterium Microcystis. Biological Reviews, 93(3): 1399–1420

[65] Xu F , Zhu W , Xiao M , Li M . (2016). Interspecific variation in extracellular polysaccharide content and colony formation of Microcystis spp. cultured under different light intensities and temperatures. Journal of Applied Phycology, 28(3): 1533–1541

[66] Yang H L , Cai Y F , Xia M , Wang X Y , Shi L M , Li P F , Kong F X . (2011). Role of cell hydrophobicity on colony formation in Microcystis (cyanobacteria). International Review of Hydro-biology, 96(2): 141–148

[67] Yin F G , Zhu Y , Koutchma T , Gong J . (2015). Inactivation and potential reactivation of pathogenic Escherichia coli O157:H7 in apple juice following ultraviolet light exposure at three monochromatic wavelengths. Food Microbiology, 46: 329–335

[68] Zhang H T , Dan Y B , Adams C D , Shi H L , Ma Y F , Eichholz T . (2017). Effect of oxidant demand on the release and degradation of microcystin-LR from Microcystis aeruginosa during oxi-dation. Chemosphere, 181: 562–568

[69] Zhang M , Shi X L , Yu Y , Kong F X . (2011). The acclimative changes in photochemistry after colony formation of the cyanobacteria Microcystis aeruginosa. Journal of Phycology, 47(3): 524–532

[70] Zhang X S , Rosenstein B S , Wang Y , Lebwohl M , Wei H C . (1997). Identification of possible reactive oxygen species involved in ultraviolet radiation-induced oxidative DNA damage. Free Radical Biology and Medicine, 23(7): 980–985

[71] Zhao K , Wang L Z , You Q M , Pan Y D , Liu T T , Zhou Y D , Zhang J Y , Pang W T , Wang Q X . (2021). Influence of cyanobacterial blooms and environmental variation on zooplankton and eukaryotic phytoplankton in a large, shallow, eutrophic lake in China. Science of the Total Environment, 773: 145421

[72] Zhou S QShao Y SGao N YDeng YQiao J LOu H SDeng J (2013). Effects of different algaecides on the photosynthetic capacity, cell integrity and microcystin-LR release of Microcystis aeruginosa. Science of the Total Environment, 463–464: 463–464

[73] Zhou S Q , Shao Y S , Gao N Y , Zhu S M , Li L , Deng J , Zhu M Q . (2014). Removal of Microcystis aeruginosa by potassium ferrate (VI): impacts on cells integrity, intracellular organic matter release and disinfection by-products formation. Chemical Engineering Journal, 251: 304–309

[74] Zhou Y L (2007). Effect of high temperature and solar UV radiation on growth and physiology of Spirulina and Arthrospira platensis. Thesis for the Master’s Degree. Qingdao: Ocean University of China

[75] Zhu W , Zhou X H , Chen H M , Gao L , Xiao M , Li M . (2016). High nutrient concentration and temperature alleviated formation of large colonies of Microcystis: evidence from field investigations and laboratory experiments. Water Research, 101: 167–175

[76] Zhu W , Zhou X H , Chen H M , Li M . (2018). Sequence of Microcystis colony formation during recruitment under natural conditions. Hydrobiologia, 823(1): 39–48

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