Biochemical characterization and mercury methylation capacity of Geobacter sulfurreducens biofilms grown in media containing iron hydroxide or fumarate
Geobacter species are common in iron-rich environments and can contribute to formation of methylmercury (MeHg), a neurotoxic compound with high bioaccumulation potential formed as a result of bacterial and archaeal physiological activity. Geobacter sulfurreducens can utilize various electron accepto...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Elsevier
2023-12-01
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| Series: | Biofilm |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2590207523000412 |
| _version_ | 1797385085180182528 |
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| author | Elena Yunda Quynh Nhu Phan Le Erik Björn Madeleine Ramstedt |
| author_facet | Elena Yunda Quynh Nhu Phan Le Erik Björn Madeleine Ramstedt |
| author_sort | Elena Yunda |
| collection | DOAJ |
| description | Geobacter species are common in iron-rich environments and can contribute to formation of methylmercury (MeHg), a neurotoxic compound with high bioaccumulation potential formed as a result of bacterial and archaeal physiological activity. Geobacter sulfurreducens can utilize various electron acceptors for growth including iron hydroxides or fumarate. However, it remains poorly understood how the growth on these compounds affects physiological properties of bacterial cells in biofilms, including the capacity to produce MeHg. The purpose of this study was to determine changes in the biochemical composition of G. sulfurreducens during biofilm cultivation in media containing iron hydroxide or fumarate, and to quantify mercury (Hg) methylation capacity of the formed biofilms. Biofilms were characterized by Fourier-transform infrared spectroscopy in the attenuated total reflection mode (ATR-FTIR), Resonance Raman spectroscopy and confocal laser scanning microscopy. MeHg formation was quantified by mass spectrometry after incubation of biofilms with 100 nM Hg. The results of ATR-FTIR experiments showed that in presence of fumarate, G. sulfurreducens biofilm formation was accompanied by variation in content of the energy-reserve polymer glycogen over time, which could be cancelled by the addition of supplementary nutrients (yeast extract). In contrast, biofilms cultivated on Fe(III) hydroxide did not accumulate glycogen. The ATR-FTIR results further suggested that Fe(III) hydroxide surfaces bind cells via phosphate and carboxylate groups of bacteria that form complexes with iron. Furthermore, biofilms grown on Fe(III) hydroxide had higher fraction of oxidized cytochromes and produced two to three times less biomass compared to conditions with fumarate. Normalized to biofilm volume, the content of MeHg was similar in assays with biofilms grown on Fe(III) hydroxide and on fumarate (with yeast extract and without). These results suggest that G. sulfurreducens biofilms produce MeHg irrespectively from glycogen content and cytochrome redox state in the cells, and warrant further investigation of the mechanisms controlling this process. |
| first_indexed | 2024-03-08T21:49:04Z |
| format | Article |
| id | doaj.art-596586439beb4422873ef107bc73a45a |
| institution | Directory Open Access Journal |
| issn | 2590-2075 |
| language | English |
| last_indexed | 2024-03-08T21:49:04Z |
| publishDate | 2023-12-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Biofilm |
| spelling | doaj.art-596586439beb4422873ef107bc73a45a2023-12-20T07:36:42ZengElsevierBiofilm2590-20752023-12-016100144Biochemical characterization and mercury methylation capacity of Geobacter sulfurreducens biofilms grown in media containing iron hydroxide or fumarateElena Yunda0Quynh Nhu Phan Le1Erik Björn2Madeleine Ramstedt3Corresponding author.; Department of Chemistry, Umeå University, SwedenDepartment of Chemistry, Umeå University, SwedenDepartment of Chemistry, Umeå University, SwedenCorresponding author.; Department of Chemistry, Umeå University, SwedenGeobacter species are common in iron-rich environments and can contribute to formation of methylmercury (MeHg), a neurotoxic compound with high bioaccumulation potential formed as a result of bacterial and archaeal physiological activity. Geobacter sulfurreducens can utilize various electron acceptors for growth including iron hydroxides or fumarate. However, it remains poorly understood how the growth on these compounds affects physiological properties of bacterial cells in biofilms, including the capacity to produce MeHg. The purpose of this study was to determine changes in the biochemical composition of G. sulfurreducens during biofilm cultivation in media containing iron hydroxide or fumarate, and to quantify mercury (Hg) methylation capacity of the formed biofilms. Biofilms were characterized by Fourier-transform infrared spectroscopy in the attenuated total reflection mode (ATR-FTIR), Resonance Raman spectroscopy and confocal laser scanning microscopy. MeHg formation was quantified by mass spectrometry after incubation of biofilms with 100 nM Hg. The results of ATR-FTIR experiments showed that in presence of fumarate, G. sulfurreducens biofilm formation was accompanied by variation in content of the energy-reserve polymer glycogen over time, which could be cancelled by the addition of supplementary nutrients (yeast extract). In contrast, biofilms cultivated on Fe(III) hydroxide did not accumulate glycogen. The ATR-FTIR results further suggested that Fe(III) hydroxide surfaces bind cells via phosphate and carboxylate groups of bacteria that form complexes with iron. Furthermore, biofilms grown on Fe(III) hydroxide had higher fraction of oxidized cytochromes and produced two to three times less biomass compared to conditions with fumarate. Normalized to biofilm volume, the content of MeHg was similar in assays with biofilms grown on Fe(III) hydroxide and on fumarate (with yeast extract and without). These results suggest that G. sulfurreducens biofilms produce MeHg irrespectively from glycogen content and cytochrome redox state in the cells, and warrant further investigation of the mechanisms controlling this process.http://www.sciencedirect.com/science/article/pii/S2590207523000412 |
| spellingShingle | Elena Yunda Quynh Nhu Phan Le Erik Björn Madeleine Ramstedt Biochemical characterization and mercury methylation capacity of Geobacter sulfurreducens biofilms grown in media containing iron hydroxide or fumarate Biofilm |
| title | Biochemical characterization and mercury methylation capacity of Geobacter sulfurreducens biofilms grown in media containing iron hydroxide or fumarate |
| title_full | Biochemical characterization and mercury methylation capacity of Geobacter sulfurreducens biofilms grown in media containing iron hydroxide or fumarate |
| title_fullStr | Biochemical characterization and mercury methylation capacity of Geobacter sulfurreducens biofilms grown in media containing iron hydroxide or fumarate |
| title_full_unstemmed | Biochemical characterization and mercury methylation capacity of Geobacter sulfurreducens biofilms grown in media containing iron hydroxide or fumarate |
| title_short | Biochemical characterization and mercury methylation capacity of Geobacter sulfurreducens biofilms grown in media containing iron hydroxide or fumarate |
| title_sort | biochemical characterization and mercury methylation capacity of geobacter sulfurreducens biofilms grown in media containing iron hydroxide or fumarate |
| url | http://www.sciencedirect.com/science/article/pii/S2590207523000412 |
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