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Silva AR, Melo LF, Keevil CW, Pereira A. Legionella colonization and 3D spatial location within a Pseudomonas biofilm. Sci Rep 2024; 14:16781. [PMID: 39039267 PMCID: PMC11263398 DOI: 10.1038/s41598-024-67712-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2024] [Accepted: 07/15/2024] [Indexed: 07/24/2024] Open
Abstract
Biofilms are known to be critical for Legionella settlement in engineered water systems and are often associated with Legionnaire's Disease events. One of the key features of biofilms is their heterogeneous three-dimensional structure which supports the establishment of microbial interactions and confers protection to microorganisms. This work addresses the impact of Legionella pneumophila colonization of a Pseudomonas fluorescens biofilm, as information about the interactions between Legionella and biofilm structures is scarce. It combines a set of meso- and microscale biofilm analyses (Optical Coherence Tomography, Episcopic Differential Interference Contrast coupled with Epifluorescence Microscopy and Confocal Laser Scanning Microscopy) with PNA-FISH labelled L. pneumophila to tackle the following questions: (a) does the biofilm structure change upon L. pneumophila biofilm colonization?; (b) what happens to L. pneumophila within the biofilm over time and (c) where is L. pneumophila preferentially located within the biofilm? Results showed that P. fluorescens structure did not significantly change upon L. pneumophila colonization, indicating the competitive advantage of the first colonizer. Imaging of PNA-labelled L. pneumophila showed that compared to standard culture recovery it colonized to a greater extent the 3-day-old P. fluorescens biofilms, presumably entering in VBNC state by the end of the experiment. L. pneumophila was mostly located in the bottom regions of the biofilm, which is consistent with the physiological requirements of both bacteria and confers enhanced Legionella protection against external aggressions. The present study provides an expedited methodological approach to address specific systematic laboratory studies concerning the interactions between L. pneumophila and biofilm structure that can provide, in the future, insights for public health Legionella management of water systems.
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Affiliation(s)
- Ana Rosa Silva
- LEPABE - Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal
- ALiCE - Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal
| | - Luis F Melo
- LEPABE - Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal
- ALiCE - Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal
| | - C William Keevil
- School of Biological Sciences, University of Southampton, Southampton, UK
| | - Ana Pereira
- LEPABE - Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal.
- ALiCE - Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal.
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Lazzem A, Lekired A, Ouzari HI, Landoulsi A, Chatti A, El May A. Isolation and characterization of a newly chrysene-degrading Achromobacter aegrifaciens. Int Microbiol 2024; 27:857-869. [PMID: 37851202 DOI: 10.1007/s10123-023-00435-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 09/21/2023] [Accepted: 09/28/2023] [Indexed: 10/19/2023]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are considered substances of potential human health hazards because of their resistance to biodegradation and carcinogenic index. Chrysene is a PAH with a high molecular weight (HMW) that poses challenges for its elimination from the environment. However, bacterial degradation is an effective, environmentally friendly, and cost-effective solution. In our study, we isolated a potential chrysene-degrading bacteria from crude oil-contaminated seawater (Bizerte, Tunisia). Based on 16SrRNA analysis, the isolate S5 was identified as Achromobacter aegrifaciens. Furthermore, the results revealed that A. aegrifaciens S5 produced a biofilm on polystyrene at 20 °C and 30 °C, as well as at the air-liquid (A-L) interface. Moreover, this isolate was able to swim and produce biosurfactants with an emulsification activity (E24%) over 53%. Chrysene biodegradation by isolate S5 was clearly assessed by an increase in the total viable count. Confirmation was obtained via gas chromatography-mass spectrometry (GC-MS) analyses. A. aegrifaciens S5 could use chrysene as its sole carbon and energy source, exhibiting an 86% degradation of chrysene on day 7. In addition, the bacterial counts reached their highest level, over 25 × 1020 CFU/mL, under the conditions of pH 7.0, a temperature of 30 °C, and a rotary speed of 120 rpm. Based on our findings, A. aegrifaciens S5 can be a potential candidate for bioremediation in HMW-PAH-contaminated environments.
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Affiliation(s)
- Assia Lazzem
- Laboratory of Risks Related to Environmental Stresses: Fight and Prevention, Faculty of Sciences of Bizerte, University of Carthage, 7021, Jarzouna, Tunisia.
| | - Abdelmalek Lekired
- Laboratory of Microorganisms and Actives Biomolecules, Faculty of Sciences of Tunis, University Tunis El Manar, 2092, Tunis, Tunisia
| | - Hadda-Imene Ouzari
- Laboratory of Microorganisms and Actives Biomolecules, Faculty of Sciences of Tunis, University Tunis El Manar, 2092, Tunis, Tunisia
| | - Ahmed Landoulsi
- Laboratory of Risks Related to Environmental Stresses: Fight and Prevention, Faculty of Sciences of Bizerte, University of Carthage, 7021, Jarzouna, Tunisia
| | - Abdelwaheb Chatti
- Laboratory of Risks Related to Environmental Stresses: Fight and Prevention, Faculty of Sciences of Bizerte, University of Carthage, 7021, Jarzouna, Tunisia
| | - Alya El May
- Laboratory of Risks Related to Environmental Stresses: Fight and Prevention, Faculty of Sciences of Bizerte, University of Carthage, 7021, Jarzouna, Tunisia
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Rekadwad BN, Li WJ, Gonzalez JM, Punchappady Devasya R, Ananthapadmanabha Bhagwath A, Urana R, Parwez K. Extremophiles: the species that evolve and survive under hostile conditions. 3 Biotech 2023; 13:316. [PMID: 37637002 PMCID: PMC10457277 DOI: 10.1007/s13205-023-03733-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Accepted: 06/26/2023] [Indexed: 08/29/2023] Open
Abstract
Extremophiles possess unique cellular and molecular mechanisms to assist, tolerate, and sustain their lives in extreme habitats. These habitats are dominated by one or more extreme physical or chemical parameters that shape existing microbial communities and their cellular and genomic features. The diversity of extremophiles reflects a long list of adaptations over millions of years. Growing research on extremophiles has considerably uncovered and increased our understanding of life and its limits on our planet. Many extremophiles have been greatly explored for their application in various industrial processes. In this review, we focused on the characteristics that microorganisms have acquired to optimally thrive in extreme environments. We have discussed cellular and molecular mechanisms involved in stability at respective extreme conditions like thermophiles, psychrophiles, acidophiles, barophiles, etc., which highlight evolutionary aspects and the significance of extremophiles for the benefit of mankind.
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Affiliation(s)
- Bhagwan Narayan Rekadwad
- Present Address: Division of Microbiology and Biotechnology, Yenepoya Research Centre, Yenepoya (Deemed to be University), University Road, Deralakatte, Mangalore, 575018 Karnataka India
- National Centre for Microbial Resource (NCMR), DBT-National Centre for Cell Science (DBT-NCCS), Savitribai Phule Pune University Campus, Ganeshkhind Road, Pune, 411007 Maharashtra India
- Institute of Bioinformatics and Biotechnology (IBB), Savitribai Phule Pune University (SPPU), Ganeshkhind Road, Pune, 411007 Maharashtra India
| | - Wen-Jun Li
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510275 People’s Republic of China
| | - Juan M. Gonzalez
- Microbial Diversity and Microbiology of Extreme Environments Research Group, Agencia Estatal Consejo Superior De Investigaciones Científicas, IRNAS-CSIC, Avda. Reina Mercedes, 10, 41012 Seville, Spain
| | - Rekha Punchappady Devasya
- Present Address: Division of Microbiology and Biotechnology, Yenepoya Research Centre, Yenepoya (Deemed to be University), University Road, Deralakatte, Mangalore, 575018 Karnataka India
| | - Arun Ananthapadmanabha Bhagwath
- Present Address: Division of Microbiology and Biotechnology, Yenepoya Research Centre, Yenepoya (Deemed to be University), University Road, Deralakatte, Mangalore, 575018 Karnataka India
- Yenepoya Institute of Arts, Science, Commerce and Management, A Constituent Unit of Yenepoya (Deemed to be University), Yenepoya Complex, Balmatta, Mangalore, 575002 Karnataka India
| | - Ruchi Urana
- Department of Environmental Science and Engineering, Faculty of Environmental and Bio Sciences and Technology, Guru Jambheshwar University of Science and Technology, Hisar, Haryana 125001 India
| | - Khalid Parwez
- Department of Microbiology, Shree Narayan Medical Institute and Hospital, Saharsa, Bihar 852201 India
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Wilsmann DE, Furian TQ, Carvalho D, Chitolina GZ, Lucca V, Emery BD, Borges KA, Martins AC, Pontin KP, Salle CTP, de Souza Moraes HL, do Nascimento VP. Antibiofilm activity of electrochemically activated water (ECAW) in the control of Salmonella Heidelberg biofilms on industrial surfaces. Braz J Microbiol 2023; 54:2035-2045. [PMID: 37184738 PMCID: PMC10485189 DOI: 10.1007/s42770-023-01005-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 05/04/2023] [Indexed: 05/16/2023] Open
Abstract
Owing to its antimicrobial activity, electrochemically activated water (ECAW) is a potential alternative to chemical disinfectants for eliminating foodborne pathogens, including Salmonella Heidelberg, from food processing facilities. However, their antibiofilm activity remains unclear. This study aimed to evaluate the antibiofilm activity of ECAW against S. Heidelberg biofilms formed on stainless steel and polyethylene and to determine its corrosive capacity. ECAW (200 ppm) and a broad-spectrum disinfectant (0.2%) were tested for their antibiofilm activity against S. Heidelberg at 25 °C and 37 °C after 10 and 20 min of contact with stainless steel and polyethylene. Potentiostatic polarization tests were performed to compare the corrosive capacity of both compounds. Both compounds were effective in removing S. Heidelberg biofilms. Bacterial counts were significantly lower with ECAW than with disinfectant in polyethylene, regardless the time of contact. The time of contact and the surface significantly influenced the bacterial counts of S. Heidelberg. Temperature was not an important factor affecting the antibiofilm activities of the compounds. ECAW was less corrosive than the disinfectant. ECAW demonstrated a similar or even superior effect in the control of S. Heidelberg biofilms, when compared to disinfectants, reducing bacterial counts by up to 5 log10 CFU cm-2. The corrosion of stainless steel with ECAW was similar to that of commercial disinfectants. This technology is a possible alternative for controlling S. Heidelberg in the food production chain.
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Affiliation(s)
- Daiane Elisa Wilsmann
- Centro de Diagnóstico e Pesquisa em Patologia Aviária, Departamento de Medicina Animal, Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9090, Porto Alegre, RS, CEP 91540-000, Brazil.
| | - Thales Quedi Furian
- Centro de Diagnóstico e Pesquisa em Patologia Aviária, Departamento de Medicina Animal, Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9090, Porto Alegre, RS, CEP 91540-000, Brazil
| | - Daiane Carvalho
- Centro de Diagnóstico e Pesquisa em Patologia Aviária, Departamento de Medicina Animal, Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9090, Porto Alegre, RS, CEP 91540-000, Brazil
| | - Gabriela Zottis Chitolina
- Centro de Diagnóstico e Pesquisa em Patologia Aviária, Departamento de Medicina Animal, Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9090, Porto Alegre, RS, CEP 91540-000, Brazil
| | - Vivian Lucca
- Centro de Diagnóstico e Pesquisa em Patologia Aviária, Departamento de Medicina Animal, Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9090, Porto Alegre, RS, CEP 91540-000, Brazil
| | - Brunna Dias Emery
- Centro de Diagnóstico e Pesquisa em Patologia Aviária, Departamento de Medicina Animal, Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9090, Porto Alegre, RS, CEP 91540-000, Brazil
| | - Karen Apellanis Borges
- Centro de Diagnóstico e Pesquisa em Patologia Aviária, Departamento de Medicina Animal, Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9090, Porto Alegre, RS, CEP 91540-000, Brazil
| | - Abrahão Carvalho Martins
- Centro de Diagnóstico e Pesquisa em Patologia Aviária, Departamento de Medicina Animal, Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9090, Porto Alegre, RS, CEP 91540-000, Brazil
| | - Karine Patrin Pontin
- Centro de Diagnóstico e Pesquisa em Patologia Aviária, Departamento de Medicina Animal, Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9090, Porto Alegre, RS, CEP 91540-000, Brazil
| | - Carlos Tadeu Pippi Salle
- Centro de Diagnóstico e Pesquisa em Patologia Aviária, Departamento de Medicina Animal, Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9090, Porto Alegre, RS, CEP 91540-000, Brazil
| | - Hamilton Luiz de Souza Moraes
- Centro de Diagnóstico e Pesquisa em Patologia Aviária, Departamento de Medicina Animal, Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9090, Porto Alegre, RS, CEP 91540-000, Brazil
| | - Vladimir Pinheiro do Nascimento
- Centro de Diagnóstico e Pesquisa em Patologia Aviária, Departamento de Medicina Animal, Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9090, Porto Alegre, RS, CEP 91540-000, Brazil
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Wray AC, Gorman-Lewis D. Bioenergetics of aerobic and anaerobic growth of Shewanella putrefaciens CN32. Front Microbiol 2023; 14:1234598. [PMID: 37601367 PMCID: PMC10433392 DOI: 10.3389/fmicb.2023.1234598] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Accepted: 07/17/2023] [Indexed: 08/22/2023] Open
Abstract
Shewanella putrefaciens is a model dissimilatory iron-reducing bacterium that can use Fe(III) and O2 as terminal electron acceptors. Consequently, it has the ability to influence both aerobic and anaerobic groundwater systems, making it an ideal microorganism for improving our understanding of facultative anaerobes with iron-based metabolism. In this work, we examine the bioenergetics of O2 and Fe(III) reduction coupled to lactate oxidation in Shewanella putrefaciens CN32. Bioenergetics were measured directly via isothermal calorimetry and by changes to the chemically defined growth medium. We performed these measurements from 25 to 36°C. Modeling metabolism with macrochemical equations allowed us to define a theoretical growth stoichiometry for the catabolic reaction of 1.00 O2:lactate and 1.33 Fe(III):lactate that was consistent with the observed ratios of O2:lactate (1.20 ± 0.23) and Fe(III):lactate (1.46 ± 0.15) consumption. Aerobic growth showed minimal variation with temperature and minimal variation in thermodynamic potentials of incubation. Fe(III)-based growth showed a strong temperature dependence. The Gibbs energy and enthalpy of incubation was minimized at ≥30°C. Energy partitioning modeling of Fe(III)-based calorimetric incubation data predicted that energy consumption for non-growth associate maintenance increases substantially above 30°C. This prediction agrees with the data at 33 and 35°C. These results suggest that the effects of temperature on Shewanella putrefaciens CN32 are metabolism dependent. Gibbs energy of incubation above 30°C was 3-5 times more exergonic with Fe(III)-based growth than with aerobic growth. We compared data gathered in this study with predictions of microbial growth based on standard-state conditions and based on the thermodynamic efficiency of microbial growth. Quantifying the growth requirements of Shewanella putrefaciens CN32 has advanced our understanding of the thermodynamic constraints of this dissimilatory iron-reducing bacterium.
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Affiliation(s)
- Addien C. Wray
- Earth and Space Sciences, University of Washington, Seattle, WA, United States
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Öztürk FY, Darcan C, Kariptaş E. The Determination, Monitoring, Molecular Mechanisms and Formation of Biofilm in E. coli. Braz J Microbiol 2023; 54:259-277. [PMID: 36577889 PMCID: PMC9943865 DOI: 10.1007/s42770-022-00895-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Accepted: 12/16/2022] [Indexed: 12/30/2022] Open
Abstract
Biofilms are cell assemblies embedded in an exopolysaccharide matrix formed by microorganisms of a single or many different species. This matrix in which they are embedded protects the bacteria from external influences and antimicrobial effects. The biofilm structure that microorganisms form to protect themselves from harsh environmental conditions and survive is found in nature in many different environments. These environments where biofilm formation occurs have in common that they are in contact with fluids. The gene expression of bacteria in complex biofilm differs from that of bacteria in the planktonic state. The differences in biofilm cell expression are one of the effects of community life. Means of quorum sensing, bacteria can act in coordination with each other. At the same time, while biofilm formation provides many benefits to bacteria, it has positive and negative effects in many different areas. Depending on where they occur, biofilms can cause serious health problems, contamination risks, corrosion, and heat and efficiency losses. However, they can also be used in water treatment plants, bioremediation, and energy production with microbial fuel cells. In this review, the basic steps of biofilm formation and biofilm regulation in the model organism Escherichia coli were discussed. Finally, the methods by which biofilm formation can be detected and monitored were briefly discussed.
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Affiliation(s)
- Fırat Yavuz Öztürk
- Department of Molecular Biology and Genetic, Faculty of Arts and Science, Bilecik Seyh Edebali University, Bilecik, Turkey.
| | - Cihan Darcan
- Department of Molecular Biology and Genetic, Faculty of Arts and Science, Bilecik Seyh Edebali University, Bilecik, Turkey
| | - Ergin Kariptaş
- Department of Medical Microbiology, Faculty of Medicine, Samsun University, Samsun, Turkey
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Alves-Barroco C, Rivas-García L, Fernandes AR, Baptista PV. Light Triggered Enhancement of Antibiotic Efficacy in Biofilm Elimination Mediated by Gold-Silver Alloy Nanoparticles. Front Microbiol 2022; 13:841124. [PMID: 35295305 PMCID: PMC8919054 DOI: 10.3389/fmicb.2022.841124] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 01/24/2022] [Indexed: 12/21/2022] Open
Abstract
Bacterial biofilm is a tri-dimensional complex community of cells at different metabolic stages involved in a matrix of self-produced extracellular polymeric substances. Biofilm formation is part of a defense mechanism that allows the bacteria to survive in hostile environments, such as increasing resistance or tolerance to antimicrobial agents, causing persistent infections hard to treat and impair disease eradication. One such example is bovine mastitis associated with Streptococcus dysgalactiae subsp. dysgalactiae (SDSD), whose worldwide health and economic impact is on the surge. As such, non-conventional nanobased approaches have been proposed as an alternative to tackle biofilm formation and to which pathogenic bacteria fail to adapt. Among these, metallic nanoparticles have gained significant attention, particularly gold and silver nanoparticles, due to their ease of synthesis and impact against microorganism growth. This study provides a proof-of-concept investigation into the use of gold-silver alloy nanoparticles (AuAgNPs) toward eradication of bacterial biofilms. Upon visible light irradiation of AuAgNPs there was considerable disturbance of the biofilms' matrix. The hindering of structural integrity of the biofilm matrix resulted in an increased permeability for entry of antibiotics, which then cause the eradication of biofilm and inhibit subsequent biofilm formation. Additionally, our results that AuAgNPs inhibited the formation of SDSD biofilms via distinct stress pathways that lead to the downregulation of two genes critical for biofilm production, namely, brpA-like encoding biofilm regulatory protein and fbpA fibronectin-binding protein A. This study provides useful information to assist the development of nanoparticle-based strategies for the active treatment of biofilm-related infections triggered by photoirradiation in the visible.
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Affiliation(s)
- Cinthia Alves-Barroco
- Applied Molecular Biosciences Unit, Dept. Ciências da Vida, NOVA School of Science and Technology, Costa da Caparica, Portugal
- i4HB, Associate Laboratory–Institute for Health and Bioeconomy, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Lorenzo Rivas-García
- Applied Molecular Biosciences Unit, Dept. Ciências da Vida, NOVA School of Science and Technology, Costa da Caparica, Portugal
- Biomedical Research Centre, Institute of Nutrition and Food Technology, Department of Physiology, Faculty of Pharmacy, University of Granada, Granada, Spain
| | - Alexandra R. Fernandes
- Applied Molecular Biosciences Unit, Dept. Ciências da Vida, NOVA School of Science and Technology, Costa da Caparica, Portugal
- i4HB, Associate Laboratory–Institute for Health and Bioeconomy, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Pedro Viana Baptista
- Applied Molecular Biosciences Unit, Dept. Ciências da Vida, NOVA School of Science and Technology, Costa da Caparica, Portugal
- i4HB, Associate Laboratory–Institute for Health and Bioeconomy, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Caparica, Portugal
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Torkzadeh H, Cates EL. Biofilm growth under continuous UVC irradiation: Quantitative effects of growth conditions and growth time on intensity response parameters. WATER RESEARCH 2021; 206:117747. [PMID: 34666263 DOI: 10.1016/j.watres.2021.117747] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 10/04/2021] [Accepted: 10/06/2021] [Indexed: 06/13/2023]
Abstract
Biofilms can harbor a wide range of microorganisms, including opportunistic respiratory pathogens, and their establishment on engineered surfaces poses a risk to public health and industry. The emergence of compact germicidal ultraviolet light-emitting diodes (UV LEDs) may enable their incorporation into confined spaces to inhibit bacterial surface colonization on inaccessible surfaces, such as those in premise plumbing. Such applications necessitate knowledge of the quantitative response of biofilm growth rates to UV exposure on continuously irradiated surfaces. Herein, we performed experiments at varying flow cell temperatures in order to control baseline biofilm growth rates in the absence of UV; then, biofilm growth was compared under the same conditions but with simultaneous UVC irradiation. The inhibiting effect of UV irradiation on biofilm growth kinetics was diminished by more favorable growth conditions (higher temperature). Increasing the temperature by 10 °C resulted in an increase in biovolume by 193% under a UVC (254 nm) intensity of ∼60 µW/cm2. We further fitted an existing intensity response model to the biofilm growth data and analyzed the effects of temperature on model parameters, which were consistent with a hypothesized shielding effect arising from the deposition of extracellular colloidal materials. The shielding effect was found to result in breakthrough behavior of irradiated biofilms after 48 h, wherein accumulation of shielding substances eventually enabled biofilm establishment at even relatively high irradiation intensities (102.3 µW/cm2). With respect to applications of UVC irradiation for biofilm prevention, these results imply that surfaces more prone to bacterial colonization require disproportionately higher-intensity UVC irradiation for prevention of biofilm establishment, and continuous surface irradiation may be inadequate as a sole intervention for biofilm prevention in many scenarios.
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Affiliation(s)
- Hamed Torkzadeh
- Department of Environmental Engineering and Earth Sciences, Clemson University, Clemson, SC 29634, USA
| | - Ezra L Cates
- Department of Environmental Engineering and Earth Sciences, Clemson University, Clemson, SC 29634, USA.
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