The in situ Production of Aquatic Fluorescent Organic Matter in a Simulated Freshwater Laboratory Model
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 i...
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2022-02-01
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| Series: | Frontiers in Microbiology |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fmicb.2022.817976/full |
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| author | Eva M. Perrin Robin M. S. Thorn Stephanie L. Sargeant John W. Attridge Darren M. Reynolds |
| author_facet | Eva M. Perrin Robin M. S. Thorn Stephanie L. Sargeant John W. Attridge Darren M. Reynolds |
| author_sort | Eva M. Perrin |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-12-24T03:07:38Z |
| format | Article |
| id | doaj.art-803efb1ccc834d8caae541b26c96c7ef |
| institution | Directory Open Access Journal |
| issn | 1664-302X |
| language | English |
| last_indexed | 2024-12-24T03:07:38Z |
| publishDate | 2022-02-01 |
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| series | Frontiers in Microbiology |
| spelling | doaj.art-803efb1ccc834d8caae541b26c96c7ef2022-12-21T17:17:57ZengFrontiers Media S.A.Frontiers in Microbiology1664-302X2022-02-011310.3389/fmicb.2022.817976817976The in situ Production of Aquatic Fluorescent Organic Matter in a Simulated Freshwater Laboratory ModelEva M. Perrin0Robin M. S. Thorn1Stephanie L. Sargeant2John W. Attridge3Darren M. Reynolds4Centre for Research in Biosciences, University of the West of England, Bristol, United KingdomCentre for Research in Biosciences, University of the West of England, Bristol, United KingdomCentre for Research in Biosciences, University of the West of England, Bristol, United KingdomChelsea Technologies Ltd., East Molesey, United KingdomCentre for Research in Biosciences, University of the West of England, Bristol, United KingdomDissolved 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.https://www.frontiersin.org/articles/10.3389/fmicb.2022.817976/fulldissolved organic matterfreshwatermicrobial processingnutrient loadingfluorescence |
| spellingShingle | Eva M. Perrin Robin M. S. Thorn Stephanie L. Sargeant John W. Attridge Darren M. Reynolds The in situ Production of Aquatic Fluorescent Organic Matter in a Simulated Freshwater Laboratory Model Frontiers in Microbiology dissolved organic matter freshwater microbial processing nutrient loading fluorescence |
| title | The in situ Production of Aquatic Fluorescent Organic Matter in a Simulated Freshwater Laboratory Model |
| title_full | The in situ Production of Aquatic Fluorescent Organic Matter in a Simulated Freshwater Laboratory Model |
| title_fullStr | The in situ Production of Aquatic Fluorescent Organic Matter in a Simulated Freshwater Laboratory Model |
| title_full_unstemmed | The in situ Production of Aquatic Fluorescent Organic Matter in a Simulated Freshwater Laboratory Model |
| title_short | The in situ Production of Aquatic Fluorescent Organic Matter in a Simulated Freshwater Laboratory Model |
| title_sort | in situ production of aquatic fluorescent organic matter in a simulated freshwater laboratory model |
| topic | dissolved organic matter freshwater microbial processing nutrient loading fluorescence |
| url | https://www.frontiersin.org/articles/10.3389/fmicb.2022.817976/full |
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