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Imtiaz S, Bilal M, Saleem M. Antimicrobial photodynamic therapy against Escherichia coli by exploiting endogenously produced Protoporphyrin IX- In vitro study. Lasers Med Sci 2024; 39:204. [PMID: 39088059 DOI: 10.1007/s10103-024-04150-8] [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: 03/21/2024] [Accepted: 07/16/2024] [Indexed: 08/02/2024]
Abstract
Due to antimicrobial drug resistance, there is a growing interest in the development of light based alternative antibacterial therapies. This research work is focused on the inactivation of Escherichia coli (E. coli) by exploiting the absorption bands 405, 505, 542, 580 and 631 nm of its indigenously produced Protoporphyrin IX (PpIX) excited by three LEDs with broad emission bands at 418, 522 and 630 nm and two laser diodes with narrow emission bands at 405 and 635 nm. Fluorescence spectroscopy and plate count method have been employed for studying the inactivation rate of E. coli strain in autoclaved water suspension. It has been found that LEDs at 418, 522 and 630 nm produced pronounced antimicrobial photodynamic effect on E. coli strain comparing laser diodes at 405 and 635 nm, which might be attributed to the overlapping of broad emission bands of LEDs with the absorption bands of PpIX than narrow emission bands of laser diodes. Particular effect of LED at 522 nm has been noticed because its broad emission band overlaps three absorption bands 505, 542 and 580 nm of PpIX. The gold standard plate count method strongly correlates with Fluorescence spectroscopy, making it an innovative tool to administer bacterial inactivation. The experimental results suggested the development of a light source that entirely overlap absorption bands of PpIx to produce a pronounced antimicrobial photodynamic effect, which might become an effective modality for in vivo disinfection of antibiotic resistant microbes in wounds and lesions.
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Affiliation(s)
- Sana Imtiaz
- National Institute of Lasers and Optronics College, Pakistan Institute of Engineering and Applied Sciences, Nilore, 45650, Islamabad, Pakistan
| | - Muhammad Bilal
- Pakistan Institute of Medical Sciences, Ibn-E-Sina Road, G-8/3, Islamabad, Pakistan
| | - Muhammad Saleem
- National Institute of Lasers and Optronics College, Pakistan Institute of Engineering and Applied Sciences, Nilore, 45650, Islamabad, Pakistan.
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2
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Harris NA, Sorensen JPR, Marchant B, Old GH, Naden PS, Bowes MJ, Scarlett PM, Nicholls DJE, Armstrong LK, Wickham HD, Read DS, Lapworth D, Bond T, Pond K. Temporal drivers of tryptophan-like fluorescent dissolved organic matter along a river continuum. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 928:172285. [PMID: 38599395 DOI: 10.1016/j.scitotenv.2024.172285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 04/04/2024] [Accepted: 04/05/2024] [Indexed: 04/12/2024]
Abstract
Tryptophan-like fluorescence (TLF) is used to indicate anthropogenic inputs of dissolved organic matter (DOM), typically from wastewater, in rivers. We hypothesised that other sources of DOM, such as groundwater and planktonic microbial biomass can also be important drivers of riverine TLF dynamics. We sampled 19 contrasting sites of the River Thames, UK, and its tributaries. Multivariate mixed linear models were developed for each site using 15 months of weekly water quality observations and with predictor variables selected according to the statistical significance of their linear relationship with TLF following a stepwise procedure. The variables considered for inclusion in the models were potassium (wastewater indicator), nitrate (groundwater indicator), chlorophyll-a (phytoplankton biomass), and Total bacterial Cells Counts (TCC) by flow cytometry. The wastewater indicator was included in the model of TLF at 89 % of sites. Groundwater was included in 53 % of models, particularly those with higher baseflow indices (0.50-0.86). At these sites, groundwater acted as a negative control on TLF, diluting other potential sources. Additionally, TCC was included positively in the models of six (32 %) sites. The models on the Thames itself using TCC were more rural sites with lower sewage inputs. Phytoplankton biomass (Chlorophyll-a) was only used in two (11 %) site models, despite the seasonal phytoplankton blooms. It is also notable that, the wastewater indicator did not always have the strongest evidence for inclusion in the models. For example, there was stronger evidence for the inclusion of groundwater and TCC than wastewater in 32 % and 5 % of catchments, respectively. Our study underscores the complex interplay of wastewater, groundwater, and planktonic microbes, driving riverine TLF dynamics, with their influence determined by site characteristics.
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Affiliation(s)
- N A Harris
- British Geological Survey, Maclean Building, Wallingford OX10 8BB, UK.
| | - J P R Sorensen
- British Geological Survey, Maclean Building, Wallingford OX10 8BB, UK
| | - B Marchant
- British Geological Survey, Maclean Building, Wallingford OX10 8BB, UK
| | - G H Old
- Centre for Ecology & Hydrology, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB, UK
| | - P S Naden
- Centre for Ecology & Hydrology, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB, UK
| | - M J Bowes
- Centre for Ecology & Hydrology, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB, UK
| | - P M Scarlett
- Centre for Ecology & Hydrology, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB, UK
| | - D J E Nicholls
- Centre for Ecology & Hydrology, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB, UK
| | - L K Armstrong
- Centre for Ecology & Hydrology, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB, UK
| | - H D Wickham
- Centre for Ecology & Hydrology, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB, UK
| | - D S Read
- Centre for Ecology & Hydrology, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB, UK
| | - D Lapworth
- British Geological Survey, Maclean Building, Wallingford OX10 8BB, UK
| | - T Bond
- Centre for Environmental Health and Engineering, Department of Civil and Environmental Engineering, University of Surrey, Guildford GU2 5XH, UK
| | - K Pond
- Centre for Environmental Health and Engineering, Department of Civil and Environmental Engineering, University of Surrey, Guildford GU2 5XH, UK
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Nguyen XC, Jang S, Noh J, Khim JS, Lee J, Kwon BO, Wang T, Hu W, Zhang X, Truong HB, Hur J. Exploring optical descriptors for rapid estimation of coastal sediment organic carbon and nearby land-use classifications via machine learning models. MARINE POLLUTION BULLETIN 2024; 202:116307. [PMID: 38564820 DOI: 10.1016/j.marpolbul.2024.116307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Revised: 03/22/2024] [Accepted: 03/26/2024] [Indexed: 04/04/2024]
Abstract
This study utilizes ultraviolet and fluorescence spectroscopic indices of dissolved organic matter (DOM) from sediments, combined with machine learning (ML) models, to develop an optimized predictive model for estimating sediment total organic carbon (TOC) and identifying adjacent land-use types in coastal sediments from the Yellow and Bohai Seas. Our results indicate that ML models surpass traditional regression techniques in estimating TOC and classifying land-use types. Penalized Least Squares Regression (PLR) and Cubist models show exceptional TOC estimation capabilities, with PLR exhibiting the lowest training error and Cubist achieving a correlation coefficient 0.79. In land-use classification, Support Vector Machines achieved 85.6 % accuracy in training and 92.2 % in testing. Maximum fluorescence intensity and ultraviolet absorbance at 254 nm were crucial factors influencing TOC variations in coastal sediments. This study underscores the efficacy of ML models utilizing DOM optical indices for near real-time estimation of marine sediment TOC and land-use classification.
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Affiliation(s)
- Xuan Cuong Nguyen
- Institute of Research and Development, Duy Tan University, Da Nang 550000, Viet Nam; Faculty of Environmental Chemical Engineering, Duy Tan University, Da Nang 550000, Viet Nam; Department of Environment and Energy, Sejong University, Seoul 05006, South Korea
| | - Suhyeon Jang
- Department of Environment and Energy, Sejong University, Seoul 05006, South Korea
| | - Junsung Noh
- Department of Environment and Energy, Sejong University, Seoul 05006, South Korea
| | - Jong Seong Khim
- School of Earth and Environmental Sciences & Research Institute of Oceanography, Seoul National University, Seoul 08826, South Korea
| | - Junghyun Lee
- Department of Environmental Education, Kongju National University, Gongju 32588, South Korea
| | - Bong-Oh Kwon
- Department of Marine Biotechnology, Kunsan National University, Kunsan 54150, Republic of Korea
| | - Tieyu Wang
- Guangdong Provincial Key Laboratory of Marine Disaster Prediction and Prevention, Shantou University, Shantou 515063, China
| | - Wenyou Hu
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Xiaowei Zhang
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China
| | - Hai Bang Truong
- Optical Materials Research Group, Science and Technology Advanced Institute, Van Lang University, Ho Chi Minh City 700000, Viet Nam; Faculty of Applied Technology, School of Technology, Van Lang University, Ho Chi Minh City 70000, Viet Nam
| | - Jin Hur
- Department of Environment and Energy, Sejong University, Seoul 05006, South Korea.
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Chen X, Du J, Kanwal S, Yang ZJ, Zheng LL, Wang J, Wen J, Zhang DW. A low-cost and portable fluorometer based on an optical pick-up unit for chlorophyll-a detection. Talanta 2024; 269:125447. [PMID: 38008018 DOI: 10.1016/j.talanta.2023.125447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 11/17/2023] [Accepted: 11/19/2023] [Indexed: 11/28/2023]
Abstract
Chlorophyll-a (Chl-a) fluorescence detection is an important technique for monitoring water quality. In this work, we proposed an approach that employs the mass-produced low-cost optical pick-up unit (OPU) extracted from the high-definition digital versatile disc (HD-DVD) drive as the key optical component for our chlorophyll-a fluorometer. The built-in blue-violet 405 nm laser diode of the OPU acts as the excitation light to perform laser-induced fluorescence (LIF). The laser driver and a series of intrinsic lenses within the OPU, such as an objective lens with a numerical aperture (NA) of 0.65 and a collimating lens, help reduce the size, cost, and system complexity of the fluorometer. By integrating off-the-shelf electronic components, miniaturized optical setups, and 3D-printed assemblies, we have developed a low-cost, easy-to-make, standalone, and portable fluorometer. Finally, we validated the performance of the device for chlorophyll-a fluorescence detection under laboratory and on-site conditions, which demonstrated its great potential in water monitoring applications. The limit of detection (LOD) for chlorophyll-a is 0.35 μg/L, the size of the device is 151 × 100 × 80 mm3, and the total cost of the proposed fluorometer is as low as 137.5 USD. © 2023 Elsevier Science. All rights reserved.
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Affiliation(s)
- Xu Chen
- School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - Jing Du
- Huitong School, Shenzhen, 518052, China
| | - Saima Kanwal
- School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - Zhi-Jin Yang
- School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - Lu-Lu Zheng
- School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - Jian Wang
- School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - Jing Wen
- School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China.
| | - Da-Wei Zhang
- School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
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Imtiaz S, Saleem M. Fluorescence Spectroscopy Based Identification of Pseudomonas Aeruginosa and Escherichia Coli Suspensions. J Fluoresc 2024:10.1007/s10895-024-03608-w. [PMID: 38334915 DOI: 10.1007/s10895-024-03608-w] [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: 12/04/2023] [Accepted: 01/29/2024] [Indexed: 02/10/2024]
Abstract
In this article, Fluorescence spectroscopy has been employed for the identification of Pseudomonas aeruginosa (PA) and Escherichia coli (E. coli) in water suspension. Emission spectra of PA and E. coli suspensions have been acquired by using excitation wavelengths from 270 to 420 nm with steps of 10 nm to explore their spectral features. It has been found that the emission spectra of tryptophan, tyrosine, NADH and FAD, being the intracellular biomolecules present in both bacteria, can be used as fingerprints for their identification, differentiation and quantification. Both bacterial strains can clearly be differentiated from water and from each other by using λex 270-290 nm through spectral analysis and from λex: 300-500 nm by applying statistical analysis. Furthermore, calibration curves for different bacterial loads of PA and E. coli suspensions have been produced between colonies forming units per ml (CFUs/ml) the integrated intensities of their emission spectra. CFUs/ml of both bacterial suspensions have been determined through plate count method which was used as cross-reference for the analysis of emission spectra of both bacterial suspensions. These curves may be used to estimate CFU/ml of both PA and E. coli in unknown water suspensions by determining the integrating intensity of their emission spectra.
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Affiliation(s)
- Sana Imtiaz
- National Institute of Lasers and Optronics College, Pakistan Institute of Engineering and Applied Sciences, 45650, Nilore, Islamabad, Pakistan
| | - Muhammad Saleem
- National Institute of Lasers and Optronics College, Pakistan Institute of Engineering and Applied Sciences, 45650, Nilore, Islamabad, Pakistan.
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Imtiaz S, Anwar S, Zada L, Ali H, Khurram MS, Saeed A, Saleem M. Fluorescence Spectroscopy for the Assessment of Microbial Load in UVC Treated Water. J Fluoresc 2023; 33:2339-2347. [PMID: 37043059 DOI: 10.1007/s10895-023-03226-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: 02/19/2023] [Accepted: 03/27/2023] [Indexed: 04/13/2023]
Abstract
In this article, Fluorescence spectroscopy has been employed for the assessment of microbial load and it has been compared with the gold standard colony forming unit (CFU) and optical density (OD) methods. In order to develop a correlation between three characterization techniques, water samples of different microbial loads have been prepared by UVC disinfection method through an indigenously developed NUVWater sterilizer, which operates in close cycle flow configuration. A UV dose of 58.9 mJ/cm2 has been determined for 99.99% disinfection for a flow rate of 0.8 l/min. The water samples were excited at 270 nm which results in the tryptophan like fluorescence at 360 nm that decreases gradually with increase of UVC dose, indicating the bacterial degradation and it has been confirmed by OD and CFU methods. In addition, it has been proved that a close cycle water flow around UV lamp is imperative so that an appropriate dose must be delivered to microorganisms for an efficient disinfection. It has been found that due to the sensitive nature of Fluorescence spectroscopy, it yields immediate results, whereas, for CFU and OD methods, water samples needs to be inoculated for 24 h. Fluorescence spectroscopy, therefore, provide a fast, online, reliable and sensitive method for the monitoring of pathogenic quantification in drinking water.
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Affiliation(s)
- Sana Imtiaz
- National Institute of Lasers and Optronics College, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad, 45650, Pakistan
| | - Shahzad Anwar
- National Institute of Lasers and Optronics College, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad, 45650, Pakistan
| | - Laiq Zada
- Department of Microbiology, Quaid-i-Azam University, Islamabad, 45320, Pakistan
| | - Hina Ali
- National Institute of Lasers and Optronics College, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad, 45650, Pakistan
| | - M Saeed Khurram
- National Institute of Lasers and Optronics College, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad, 45650, Pakistan
| | - Azhar Saeed
- PAEC General Hospital, H-11/4, Islamabad, Pakistan
| | - Muhammad Saleem
- National Institute of Lasers and Optronics College, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad, 45650, Pakistan.
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Imtiaz S, Saleem M. Fluorescence Spectroscopy Based Characterization of Pseudomonas Aeruginosa Suspension. J Fluoresc 2023:10.1007/s10895-023-03436-4. [PMID: 37713016 DOI: 10.1007/s10895-023-03436-4] [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: 07/16/2023] [Accepted: 09/06/2023] [Indexed: 09/16/2023]
Abstract
In this article, optical characterization of Pseudomonas aeruginosa (PA) suspension has been performed by using Fluorescence spectroscopy. Optical density (OD) and plate count methods have been employed as a reference for the analysis of emission spectra of Pseudomonas aeruginosa in water suspension. Emission spectra of PA suspension has been acquired by using excitation wavelengths from 270 to 420 nm with step of 10 nm to explore its spectral behavior. It has been found that emission spectra of tryptophan, tyrosine, NADH and FAD, the intracellular biomolecules of bacteria, can be used as finger prints for the detection of Pseudomonas aeruginosa. Furthermore, the effect of water matrix on the spectral emission of Pseudomonas aeruginosa has been investigated that might be one of the limitation of Fluorescence spectroscopy for complex water matrices. Moreover, a calibration curve has been produced between ODs600 of Pseudomonas aeruginosa suspensions of different bacterial load and integrated intensities of the emission spectra of same samples. These ODs600 and integrating intensities have been further vetted through plate count method by determining their corresponding colony forming units per ml (CFU/ml). This calibration curve may be used to determine CFU/ml of Pseudomonas aeruginosa in water sample by determining integrating intensity of its emission spectrum.
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Affiliation(s)
- Sana Imtiaz
- National Institute of Lasers and Optronics College, Pakistan Institute of Engineering and Applied Sciences, 45650, Nilore, Islamabad, Pakistan
| | - Muhammad Saleem
- National Institute of Lasers and Optronics College, Pakistan Institute of Engineering and Applied Sciences, 45650, Nilore, Islamabad, Pakistan.
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Vucinic L, O'Connell D, Dubber D, Coxon C, Gill L. Multiple fluorescence approaches to identify rapid changes in microbial indicators at karst springs. JOURNAL OF CONTAMINANT HYDROLOGY 2023; 254:104129. [PMID: 36634484 DOI: 10.1016/j.jconhyd.2022.104129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 12/28/2022] [Accepted: 12/29/2022] [Indexed: 06/17/2023]
Abstract
Karst springs are globally important for drinking water supply but are often also exceptionally vulnerable to contamination. Such springs usually exhibit strong variation in microbial water quality in sharp response to rainfall events, thus, posing a health hazard to consumers of water supplied from these sources. The rapid detection of such changes is extremely important as well as being able to establish a link to the sources of such pollution, so that appropriate measures can be taken both in terms of immediate protection of human health and the management of karst aquifers. In this study, a fluorescence-based multi-parameter approach was trialed in order to evaluate which methods can be used to monitor rainfall-induced rapid changes in microbial water quality at karst springs, as well as determine whether such changes can be linked to sources of human effluent contamination. The results from three monitoring periods at two karst springs revealed marked responses to rainfall events for all of the microbial parameters measured. Total cell count (TCC) measurements using flow cytometry (FCM) showed very strong positive correlations with the more conventionally monitored faecal indicator bacteria (FIB) and total coliforms (TC), indicating that such a fluorescence-based and cultivation-independent technique can be very useful to indicate rapid changes in microbial water quality at karst springs. Furthermore, very strong positive correlations were also found between tryptophan-like fluorescence (TLF) measurements and concentrations of all monitored microbial parameters, again demonstrating that such a fluorescence-based approach can also be useful for detecting rapid changes in concentrations of traditional faecal indicators. Interestingly, it was found that fluorescent whitening compounds (FWCs) signals do not necessarily follow temporal variations of microbial indicators. However, the frequency of detection of positive FWCs signals may still reveal useful information about the overall magnitude of human wastewater effluent impacts on karst aquifer systems.
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Affiliation(s)
- Luka Vucinic
- Department of Civil, Structural and Environmental Engineering, University of Dublin, Trinity College, Dublin, Ireland.
| | - David O'Connell
- Department of Civil, Structural and Environmental Engineering, University of Dublin, Trinity College, Dublin, Ireland
| | - Donata Dubber
- Department of Civil, Structural and Environmental Engineering, University of Dublin, Trinity College, Dublin, Ireland
| | - Catherine Coxon
- Department of Geology, Trinity Centre for the Environment, University of Dublin, Trinity College, Dublin, Ireland
| | - Laurence Gill
- Department of Civil, Structural and Environmental Engineering, University of Dublin, Trinity College, Dublin, Ireland
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Sattar AA, Good CR, Saletes M, Brandão J, Jackson SK. Endotoxin as a Marker for Water Quality. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:16528. [PMID: 36554408 PMCID: PMC9778876 DOI: 10.3390/ijerph192416528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 12/02/2022] [Accepted: 12/07/2022] [Indexed: 06/17/2023]
Abstract
BACKGROUND Water quality testing is vital to protect human health. Current testing relies mainly on culture-based detection of faecal indicator organisms such as Escherichia coli (E.coli). However, bacterial cultures are a slow process, taking 24-48 h and requiring specialised laboratories and trained personnel. Access to such laboratories is often sparse in developing countries and there are many fatalities deriving from poor water quality. Endotoxin is a molecular component of Gram-negative bacterial cell walls and can be used to detect their presence in drinking water. METHOD The current study used a novel assay (BacterisK) to rapidly detect endotoxin in various water samples and correlate the results with E. coli content measured by culture methods. The data generated by the BacterisK assay are presented as an 'endotoxin risk' (ER). RESULTS The ER values correlate with E. coli and thus endotoxin can be used as a marker of faecal contamination in water. Moreover, the BacterisK assay provides data in near real-time and can be used in situ allowing water quality testing at different spatial and temporal locations. CONCLUSION We suggest that BacterisK can be used as a convenient risk assessment tool to assess water quality where results are required quickly or access to laboratories is lacking.
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Affiliation(s)
- Anas A. Sattar
- Molendotech Limited, Brixham Laboratory, Blackball Lane, Freshwater Quarry, Brixham TQ5 8BA, UK
| | - Christian R. Good
- Molendotech Limited, Brixham Laboratory, Blackball Lane, Freshwater Quarry, Brixham TQ5 8BA, UK
| | - Margaux Saletes
- Molendotech Limited, Brixham Laboratory, Blackball Lane, Freshwater Quarry, Brixham TQ5 8BA, UK
| | - João Brandão
- Department of Environmental Health, National Institute of Health Dr. Ricardo, Avenida Padre Cruz, 1649-016 Lisboa, Portugal
- Centre for Environmental and Marine Studies (CESAM), Department of Animal Biology, University of Lisboa, 1749-016 Lisboa, Portugal
| | - Simon K. Jackson
- Molendotech Limited, Brixham Laboratory, Blackball Lane, Freshwater Quarry, Brixham TQ5 8BA, UK
- School of Biomedical Science, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK
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Bedell E, Harmon O, Fankhauser K, Shivers Z, Thomas E. A continuous, in-situ, near-time fluorescence sensor coupled with a machine learning model for detection of fecal contamination risk in drinking water: Design, characterization and field validation. WATER RESEARCH 2022; 220:118644. [PMID: 35667167 DOI: 10.1016/j.watres.2022.118644] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 05/18/2022] [Accepted: 05/19/2022] [Indexed: 06/15/2023]
Abstract
We designed and validated a sensitive, continuous, in-situ, remotely reporting tryptophan-like fluorescence sensor and coupled it with a machine learning model to predict high-risk fecal contamination in water (>10 colony forming units (CFU)/100mL E. coli). We characterized the sensor's response to multiple fluorescence interferents with benchtop analysis. The sensor's minimum detection limit (MDL) of tryptophan dissolved in deionized water was 0.05 ppb (p <0.01) and its MDL of the correlation to E. coli present in wastewater effluent was 10 CFU/100 mL (p <0.01). Fluorescence response declined exponentially with increased water temperature and a correction factor was calculated. Inner filter effects, which cause signal attenuation at high concentrations, were shown to have negligible impact in an operational context. Biofouling was demonstrated to increase the fluorescence signal by approximately 82% in a certain context, while mineral scaling reduced the sensitivity of the sensor by approximately 5% after 24 hours with a scaling solution containing 8 times the mineral concentration of the Colorado River. A machine learning model was developed, with TLF measurements as the primary feature, to output fecal contamination risk levels established by the World Health Organization. A training and validation data set for the model was built by installing four sensors on Boulder Creek, Colorado for 88 days and enumerating 298 grab samples for E. coli with membrane filtration. The machine learning model incorporated a proxy feature for fouling (time since last cleaning) which improved model performance. A binary classification model was able to predict high risk fecal contamination with 83% accuracy (95% CI: 78% - 87%), sensitivity of 80%, and specificity of 86%. A model distinguishing between all World Health Organization established risk categories performed with an overall accuracy of 64%. Integrating TLF measurements into an ML model allows for anomaly detection and noise reduction, permitting contamination prediction despite biofilm or mineral scaling formation on the sensor's lenses. Real-time detection of high risk fecal contamination could contribute to a major step forward in terms of microbial water quality monitoring for human health.
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Affiliation(s)
- Emily Bedell
- Mortenson Center in Global Engineering, University of Colorado Boulder, 4001 Discovery Drive, Boulder, 80303, Colorado, United States of America; SweetSense Inc., Boulder, Colorado, USA
| | - Olivia Harmon
- Mortenson Center in Global Engineering, University of Colorado Boulder, 4001 Discovery Drive, Boulder, 80303, Colorado, United States of America
| | - Katie Fankhauser
- Mortenson Center in Global Engineering, University of Colorado Boulder, 4001 Discovery Drive, Boulder, 80303, Colorado, United States of America; SweetSense Inc., Boulder, Colorado, USA
| | | | - Evan Thomas
- Mortenson Center in Global Engineering, University of Colorado Boulder, 4001 Discovery Drive, Boulder, 80303, Colorado, United States of America; SweetSense Inc., Boulder, Colorado, USA.
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11
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Kurajica L, Ujević Bošnjak M, Kinsela AS, Bieroza M, Štiglić J, Waite TD, Capak K, Romić Ž. Mixing of arsenic-rich groundwater and surface water in drinking water distribution systems: Implications for contaminants, disinfection byproducts and organic components. CHEMOSPHERE 2022; 292:133406. [PMID: 34958791 DOI: 10.1016/j.chemosphere.2021.133406] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 12/17/2021] [Accepted: 12/21/2021] [Indexed: 06/14/2023]
Abstract
The utilization of groundwaters containing high levels of arsenic (As) for drinking water purposes presents major health and economic challenges for water utilities. One low-cost approach is to mix arsenic-rich groundwater (GW) with arsenic-free surface waters (SW) to achieve acceptable As levels. In this study we investigated the effect of different mixing ratios on water quality in an eastern Croatian water distribution system (WDS). To investigate the effects of mixing on drinking water quality, we measured the organic matter (OM) composition, disinfection byproduct (DBP) and metal concentrations in differently mixed ratios of GW and SW within the WDS. Fluorescence analysis revealed that the GW and SW had similar OM composition, with an almost equal ratio of humic- and protein-like OM throughout the WDS despite fluorescence indices revealing slightly different OM sources between the two water types. The tyrosine-like OM component was more variable, increasing during warmer months and towards the end of the WDS, most likely due to enhanced biofilm formation. Arsenic concentrations decreased to below 10 μg/L in the second half of the sampling campaign. Acceptable water quality was achieved after a period of destabilization and solubilization of loose deposits within the WDS resulting in their mobilization caused by water quality changes. Principal component and classification analysis, regression models and Spearman correlation coefficients revealed an association between As, OM and DBP concentrations with these correlations suggestive of their role in As mobilization in the WDS. Changing source waters, with different OM content and characteristics, corresponded to variable As release within the WDS.
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Affiliation(s)
- L Kurajica
- Croatian Institute of Public Health, Rockefeller Street 7, 10000, Zagreb, Croatia
| | - M Ujević Bošnjak
- Croatian Institute of Public Health, Rockefeller Street 7, 10000, Zagreb, Croatia.
| | - A S Kinsela
- Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW, 2052, Australia
| | - M Bieroza
- Department of Soil and Environment, Swedish University of Agricultural Sciences, Uppsala, 75007, Sweden
| | - J Štiglić
- Croatian Institute of Public Health, Rockefeller Street 7, 10000, Zagreb, Croatia
| | - T D Waite
- Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW, 2052, Australia
| | - K Capak
- Croatian Institute of Public Health, Rockefeller Street 7, 10000, Zagreb, Croatia
| | - Ž Romić
- Osijek Water Supply Company, Poljski Put 1, Osijek, Croatia
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12
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Perrin EM, Thorn RMS, Sargeant SL, Attridge JW, Reynolds DM. The in situ Production of Aquatic Fluorescent Organic Matter in a Simulated Freshwater Laboratory Model. Front Microbiol 2022; 13:817976. [PMID: 35283853 PMCID: PMC8912988 DOI: 10.3389/fmicb.2022.817976] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 01/31/2022] [Indexed: 11/15/2022] Open
Abstract
Dissolved organic matter (DOM) is ubiquitous throughout aquatic systems. Fluorescence techniques can be used to characterize the fluorescing proportion of DOM, aquatic fluorescent organic matter (AFOM). AFOM is conventionally named in association with specific fluorescence “peaks,” which fluoresce in similar optical regions as microbially-derived proteinaceous material (Peak T), and terrestrially-derived humic-like compounds (Peaks C/C+), with Peak T previously being investigated as a tool for bacterial enumeration within freshwaters. The impact of anthropogenic nutrient loading on the processing of DOM by microbial communities is largely unknown. Previous laboratory studies utilizing environmental freshwater have employed growth media with complex background fluorescence, or very high nutrient concentrations, preventing the investigation of AFOM production under a range of more representative nutrient concentrations within a matrix exhibiting very low background fluorescence. We describe a laboratory-based model with Pseudomonas aeruginosa that incorporates a low fluorescence growth matrix consisting of a simulated freshwater (SFW), representative of low-hardness freshwater systems allowing controlled nutrient conditions to be studied. The effects of microbial processing of DOM as a function of available nitrogen, phosphorous, and dissolved organic carbon (DOC) in the form of glucose were investigated over 48 h at highly resolved time increments. The model system demonstrates the production of a range of complex AFOM peaks in the presence and absence of DOC, revealing no linear relationship between cell numbers and any of the peaks for the bacterial species studied, with AFOM peaks increasing with microbial cell number, ranging from 55.2 quinine sulfate units (QSU) per 106 cells to 155 QSU per 106 cells (p < 0.05) for Peak T during the exponential growth phase of P. aeruginosa under high nutrient conditions with 5 mg L−1 DOC. Nutrient and DOC concentration was found to cause differential production of autochthonous- or allochthonous-like AFOM, with lower DOC concentrations resulting in higher Peak T production relative to Peaks C/C+ upon the addition of nutrients, and high DOC concentrations resulting in higher Peak C/C+ production relative to Peak T. Our results show the production of allochthonous-like AFOM from a simple and non-fluorescent carbon source, and provide uncertainty in the use of Peak T as a reliable surrogate for specific bacterial enumeration, particularly in dynamic or nutrient-impacted environments, pointing toward the use of fluorescence as an indicator for microbial metabolism.
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Affiliation(s)
- Eva M Perrin
- Centre for Research in Biosciences, University of the West of England, Bristol, United Kingdom
| | - Robin M S Thorn
- Centre for Research in Biosciences, University of the West of England, Bristol, United Kingdom
| | - Stephanie L Sargeant
- Centre for Research in Biosciences, University of the West of England, Bristol, United Kingdom
| | | | - Darren M Reynolds
- Centre for Research in Biosciences, University of the West of England, Bristol, United Kingdom
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13
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Effect of the Recycling Process on Drinking Water Treatment: Evaluation Based on Fluorescence EEM Analysis Using the Peak-Picking Technique and Self-Organizing Map. WATER 2021. [DOI: 10.3390/w13233456] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The recycling process is applied in many water treatment plants (WTPs), although this process can lead to adverse effects. The effect of the recycling process on the characteristics of dissolved organic matter was evaluated based on a fluorescence excitation-emission matrix using the peak-picking technique and self-organizing map (SOM). In this study, an evaluation of two WTPs, one with and one without a recycling system, was carried out. Both WTPs show moderate efficiency during the coagulation–flocculation process in removing DOC, fulvic acid-like, humic acid-like, and tryptophan-like substances. The recycling process causes increased values of fulvic acid-like, humic acid-like, and tryptophan-like substances and specific ultraviolet absorbance (SUVA) after the filtration process of about 31.0%, 35.7%, 22.2%, and 6%, respectively. Meanwhile, the WTP without recycling showed a reduction in the level of fulvic acid-like, humic acid-like, and tryptophan-like substances and SUVA by 23.3%, 52.9%, 27.8%, and 21.1%, respectively. Moreover, SOM analysis based on the peak-picking technique can determine differences in sample clusters due to the recycling process.
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14
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Khoshmaram L, Mohammadi M, Nazemi Babadi A. A portable low-cost fluorimeter based on LEDs and a smart phone. Microchem J 2021. [DOI: 10.1016/j.microc.2021.106773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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15
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Sorensen JPR, Nayebare J, Carr AF, Lyness R, Campos LC, Ciric L, Goodall T, Kulabako R, Curran CMR, MacDonald AM, Owor M, Read DS, Taylor RG. In-situ fluorescence spectroscopy is a more rapid and resilient indicator of faecal contamination risk in drinking water than faecal indicator organisms. WATER RESEARCH 2021; 206:117734. [PMID: 34655933 DOI: 10.1016/j.watres.2021.117734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 09/24/2021] [Accepted: 09/29/2021] [Indexed: 06/13/2023]
Abstract
Faecal indicator organisms (FIOs) are limited in their ability to protect public health from the microbial contamination of drinking water because of their transience and time required to deliver a result. We evaluated alternative rapid, and potentially more resilient, approaches against a benchmark FIO of thermotolerant coliforms (TTCs) to characterise faecal contamination over 14 months at 40 groundwater sources in a Ugandan town. Rapid approaches included: in-situ tryptophan-like fluorescence (TLF), humic-like fluorescence (HLF), turbidity; sanitary inspections; and total bacterial cells by flow cytometry. TTCs varied widely in six sampling visits: a third of sources tested both positive and negative, 50% of sources had a range of at least 720 cfu/100 mL, and a two-day heavy rainfall event increased median TTCs five-fold. Using source medians, TLF was the best predictor in logistic regression models of TTCs ≥10 cfu/100 mL (AUC 0.88) and best correlated to TTC enumeration (ρs 0.81), with HLF performing similarly. Relationships between TLF or HLF and TTCs were stronger in the wet season than the dry season, when TLF and HLF were instead more associated with total bacterial cells. Source rank-order between sampling rounds was considerably more consistent, according to cross-correlations, using TLF or HLF (min ρs 0.81) than TTCs (min ρs 0.34). Furthermore, dry season TLF and HLF cross-correlated more strongly (ρs 0.68) than dry season TTCs (ρs 0.50) with wet season TTCs, when TTCs were elevated. In-situ TLF or HLF are more rapid and resilient indicators of faecal contamination risk than TTCs.
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Affiliation(s)
- James P R Sorensen
- British Geological Survey, Maclean Building, Wallingford, OX10 8BB, United Kingdom of Great Britain and Northern Ireland UK; Department of Geography, University College London, London WC1E 6BT, United Kingdom of Great Britain and Northern Ireland UK.
| | - Jacintha Nayebare
- Department of Geology and Petroleum Studies, Makerere University, Uganda
| | - Andrew F Carr
- Department of Geography, University College London, London WC1E 6BT, United Kingdom of Great Britain and Northern Ireland UK
| | - Robert Lyness
- Department of Civil, Environmental & Geomatic Engineering, University College London, London WC1E 6BT, United Kingdom of Great Britain and Northern Ireland UK
| | - Luiza C Campos
- Department of Civil, Environmental & Geomatic Engineering, University College London, London WC1E 6BT, United Kingdom of Great Britain and Northern Ireland UK
| | - Lena Ciric
- Department of Civil, Environmental & Geomatic Engineering, University College London, London WC1E 6BT, United Kingdom of Great Britain and Northern Ireland UK
| | - Timothy Goodall
- UK Centre for Ecology & Hydrology (UKCEH), Maclean Building, Wallingford, OX10 8BB, United Kingdom of Great Britain and Northern Ireland UK
| | - Robinah Kulabako
- Department of Civil and Environmental Engineering, Makerere University, Uganda
| | - Catherine M Rushworth Curran
- Catherine M Rushworth Curran Ltd., 27 Silverhall Street, Isleworth, TW7 6RF, United Kingdom of Great Britain and Northern Ireland UK
| | - Alan M MacDonald
- British Geological Survey, Lyell Centre, Research Avenue South, Edinburgh EH14 4AP, United Kingdom of Great Britain and Northern Ireland UK
| | - Michael Owor
- Department of Geology and Petroleum Studies, Makerere University, Uganda
| | - Daniel S Read
- UK Centre for Ecology & Hydrology (UKCEH), Maclean Building, Wallingford, OX10 8BB, United Kingdom of Great Britain and Northern Ireland UK
| | - Richard G Taylor
- Department of Geography, University College London, London WC1E 6BT, United Kingdom of Great Britain and Northern Ireland UK
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16
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Laboratory In-Situ Production of Autochthonous and Allochthonous Fluorescent Organic Matter by Freshwater Bacteria. Microorganisms 2021; 9:microorganisms9081623. [PMID: 34442702 PMCID: PMC8400322 DOI: 10.3390/microorganisms9081623] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 07/16/2021] [Accepted: 07/26/2021] [Indexed: 11/17/2022] Open
Abstract
This work investigates the origin and range of fluorescent organic matter (FOM) produced in-situ by environmentally sourced freshwater bacteria. Aquatic FOM is an essential component in global carbon cycling and is generally classified as either autochthonous, produced in-situ via microbial processes, or allochthonous, transported into aquatic systems from external sources. We have demonstrated that, within laboratory model systems, environmentally sourced mixed microbial communities and bacterial isolates can produce and/or export FOM associated with both autochthonous and allochthonous material. This study focuses on fluorescence peak B, T, M, C and C+, exploring (1) the cellular nature of FOM produced, (2) FOM exported as extracellular material into the water column and (3) the impact of physical cell lysis on FOM signature. For the laboratory model systems studied, Peak T fluorescence is retained within bacterial cells (>68%), while Peak C fluorescence is mainly observed as extracellular material (>80%). Peak M is identified as both cellular and extracellular FOM, produced by all isolated freshwater microorganisms investigated. The origin of Peak C+ is postulated to originate from functional metabolites associated with specific microorganisms, seen specifically within the Pseudomonas sp. monoculture here. This work challenges the binary classification of FOM as either allochthonous or autochthonous, suggesting that FOM processing and production occurs along a dynamic continuum. Within this study, fluorescence intensity data for the environmental bacteria isolate monocultures are presented as enumeration corrected data, for the first time providing quantitative fluorescence data per bacterial colony forming unit (cfu). From this, we are able to assess the relative contribution of different bacteria to the autochthonous FOM pool and if this material is cellular or extracellular.
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17
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Maqbool T, Li C, Qin Y, Zhang J, Asif MB, Zhang Z. A year-long cyclic pattern of dissolved organic matter in the tap water of a metropolitan city revealed by fluorescence spectroscopy. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 771:144850. [PMID: 33548702 DOI: 10.1016/j.scitotenv.2020.144850] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 12/22/2020] [Accepted: 12/24/2020] [Indexed: 06/12/2023]
Abstract
Delivering drinking water with stable quality in metropolitan cities is a big challenge. This study investigated the year-long dynamics of dissolved organic matter (DOM) in the tap water and source water of a metropolitan city in southern China using fluorescence spectroscopy. The DOM detected in the tap water, and source water of Shenzhen city was season and location-dependent. A year-long cyclic trend of DOM was found with predominate protein-like fluorescence in the dry season compared to the humic-like enriched DOM in the wet season. A general DOM pattern was estimated by measuring the shift in dominant fluorescence regions on the excitation-emission matrix (EEM). The difference in fluorescent DOM (FDOM) composition (in terms of the ratio of protein-like to humic-like fluorescence) was above 200% between wet and dry seasons. The taps associated with reservoirs receiving water from the eastern tributary of Dongjiang River showed significant changes in protein-like contents than the taps with source water originating from the western part of the river. This study highlights the importance of optimizing drinking water treatment plants' operational conditions after considering seasonal changes and source water characteristics.
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Affiliation(s)
- Tahir Maqbool
- Institute of Environmental Engineering & Nano-Technology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, Guangdong, China; Guangdong Provincial Engineering Research Centre for Urban Water Recycling and Environmental Safety, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, Guangdong, China; School of Environment, Tsinghua University, Beijing 100084, China
| | - Chengyue Li
- Institute of Environmental Engineering & Nano-Technology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, Guangdong, China; Guangdong Provincial Engineering Research Centre for Urban Water Recycling and Environmental Safety, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, Guangdong, China; School of Environment, Tsinghua University, Beijing 100084, China
| | - Yanling Qin
- Institute of Environmental Engineering & Nano-Technology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, Guangdong, China; Guangdong Provincial Engineering Research Centre for Urban Water Recycling and Environmental Safety, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, Guangdong, China; School of Environment, Tsinghua University, Beijing 100084, China
| | - Jiaxing Zhang
- Institute of Environmental Engineering & Nano-Technology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, Guangdong, China; Guangdong Provincial Engineering Research Centre for Urban Water Recycling and Environmental Safety, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, Guangdong, China; School of Environment, Tsinghua University, Beijing 100084, China
| | - Muhammad Bilal Asif
- Institute of Environmental Engineering & Nano-Technology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, Guangdong, China; Guangdong Provincial Engineering Research Centre for Urban Water Recycling and Environmental Safety, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, Guangdong, China; School of Environment, Tsinghua University, Beijing 100084, China
| | - Zhenghua Zhang
- Institute of Environmental Engineering & Nano-Technology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, Guangdong, China; Guangdong Provincial Engineering Research Centre for Urban Water Recycling and Environmental Safety, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, Guangdong, China; School of Environment, Tsinghua University, Beijing 100084, China.
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18
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Sorensen JPR, Carr AF, Nayebare J, Diongue DML, Pouye A, Roffo R, Gwengweya G, Ward JST, Kanoti J, Okotto-Okotto J, van der Marel L, Ciric L, Faye SC, Gaye CB, Goodall T, Kulabako R, Lapworth DJ, MacDonald AM, Monjerezi M, Olago D, Owor M, Read DS, Taylor RG. Tryptophan-like and humic-like fluorophores are extracellular in groundwater: implications as real-time faecal indicators. Sci Rep 2020; 10:15379. [PMID: 32958794 PMCID: PMC7505957 DOI: 10.1038/s41598-020-72258-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 06/17/2020] [Indexed: 12/17/2022] Open
Abstract
Fluorescent natural organic matter at tryptophan-like (TLF) and humic-like fluorescence (HLF) peaks is associated with the presence and enumeration of faecal indicator bacteria in groundwater. We hypothesise, however, that it is predominantly extracellular material that fluoresces at these wavelengths, not bacterial cells. We quantified total (unfiltered) and extracellular (filtered at < 0.22 µm) TLF and HLF in 140 groundwater sources across a range of urban population densities in Kenya, Malawi, Senegal, and Uganda. Where changes in fluorescence occurred following filtration they were correlated with potential controlling variables. A significant reduction in TLF following filtration (ΔTLF) was observed across the entire dataset, although the majority of the signal remained and thus considered extracellular (median 96.9%). ΔTLF was only significant in more urbanised study areas where TLF was greatest. Beneath Dakar, Senegal, ΔTLF was significantly correlated to total bacterial cells (ρs 0.51). No significant change in HLF following filtration across all data indicates these fluorophores are extracellular. Our results suggest that TLF and HLF are more mobile than faecal indicator bacteria and larger pathogens in groundwater, as the predominantly extracellular fluorophores are less prone to straining. Consequently, TLF/HLF are more precautionary indicators of microbial risks than faecal indicator bacteria in groundwater-derived drinking water.
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Affiliation(s)
- James P R Sorensen
- British Geological Survey, Maclean Building, Wallingford, OX10 8BB, UK.
- Department of Geography, University College London, London, WC1E 6BT, UK.
| | - Andrew F Carr
- Department of Geography, University College London, London, WC1E 6BT, UK
| | - Jacintha Nayebare
- Department of Geology and Petroleum Studies, Makerere University, Kampala, Uganda
| | - Djim M L Diongue
- Department of Geology, Universite Cheikh Anta Diop, Dakar, Senegal
| | - Abdoulaye Pouye
- Department of Geology, Universite Cheikh Anta Diop, Dakar, Senegal
| | - Raphaëlle Roffo
- Department of Geography, University College London, London, WC1E 6BT, UK
| | - Gloria Gwengweya
- Chancellor College, University of Malawi, P.O. Box 280, Zomba, Malawi
| | - Jade S T Ward
- British Geological Survey, Keyworth, NG12 5GG, UK
- Department of Civil and Environmental Engineering, University of Surrey, Guildford, GU2 7XH, UK
| | - Japhet Kanoti
- Department of Geology, University of Nairobi, Nairobi, Kenya
| | - Joseph Okotto-Okotto
- Victoria Institute for Research on Environment and Development (VIRED) International, Rabuour Environment and Development Centre, Kisumu-Nairobi Road, P.O. Box, Kisumu, 6423-40103, Kenya
| | | | - Lena Ciric
- Department of Civil, Environmental and Geomatic Engineering, University College London, London, WC1E 6BT, UK
| | - Seynabou C Faye
- Department of Geology, Universite Cheikh Anta Diop, Dakar, Senegal
| | - Cheikh B Gaye
- Department of Geology, Universite Cheikh Anta Diop, Dakar, Senegal
| | - Timothy Goodall
- Centre for Ecology and Hydrology, Maclean Building, Wallingford, OX10 8BB, UK
| | - Robinah Kulabako
- Department of Civil and Environmental Engineering, Makerere University, Kampala, Uganda
| | - Daniel J Lapworth
- British Geological Survey, Maclean Building, Wallingford, OX10 8BB, UK
| | - Alan M MacDonald
- British Geological Survey, Lyell Centre, Research Avenue South, Edinburgh, EH14 4AP, UK
| | - Maurice Monjerezi
- Chancellor College, University of Malawi, P.O. Box 280, Zomba, Malawi
| | - Daniel Olago
- Department of Geology, University of Nairobi, Nairobi, Kenya
| | - Michael Owor
- Department of Geology and Petroleum Studies, Makerere University, Kampala, Uganda
| | - Daniel S Read
- Centre for Ecology and Hydrology, Maclean Building, Wallingford, OX10 8BB, UK
| | - Richard G Taylor
- Department of Geography, University College London, London, WC1E 6BT, UK
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