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Sharma A, Taubert M, Pérez-Carrascal OM, Lehmann R, Ritschel T, Totsche KU, Lazar CS, Küsel K. Iron coatings on carbonate rocks shape the attached bacterial aquifer community. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 917:170384. [PMID: 38281639 DOI: 10.1016/j.scitotenv.2024.170384] [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: 10/19/2023] [Revised: 01/12/2024] [Accepted: 01/21/2024] [Indexed: 01/30/2024]
Abstract
Most studies of groundwater ecosystems target planktonic microbes, which are easily obtained via water samples. In contrast, little is known about the diversity and function of microbes adhering to rock surfaces, particularly to consolidated rocks. To investigate microbial attachment to rock surfaces, we incubated rock chips from fractured aquifers in limestone-mudstone alternations in bioreactors fed with groundwater from two wells representing oxic and anoxic conditions. Half of the chips were coated with iron oxides, representing common secondary mineralization in fractured rock. Our time-series analysis showed bacteria colonizing the chips within two days, reaching cell numbers up to 4.16 × 105 cells/mm2 after 44 days. Scanning electron microscopy analyses revealed extensive colonization but no multi-layered biofilms, with chips from oxic bioreactors more densely colonized than from anoxic ones. Estimated attached-to-planktonic cell ratios yielded values of up to 106: 1 and 103: 1, for oxic and anoxic aquifers, respectively. We identified distinct attached and planktonic communities with an overlap between 17 % and 42 %. Oxic bioreactors were dominated by proteobacterial genera Aquabacterium and Rhodoferax, while Rheinheimera and Simplicispira were the key players of anoxic bioreactors. Motility, attachment, and biofilm formation traits were predicted in major genera based on groundwater metagenome-assembled genomes and reference genomes. Early rock colonizers appeared to be facultative autotrophs, capable of fixing CO2 to synthesize biomass and a biofilm matrix. Late colonizers were predicted to possess biofilm degrading enzymes such as beta-glucosidase, beta-galactosidase, amylases. Fe-coated chips of both bioreactors featured more potential iron reducers and oxidizers than bare rock chips. As secondary minerals can also serve as energy source, they might favor primary production and thus contribute to subsurface ecosystem services like carbon fixation. Since most subsurface microbes seem to be attached, their contribution to ecosystem services should be considered in future studies.
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Affiliation(s)
- Alisha Sharma
- Aquatic Geomicrobiology, Institute of Biodiversity, Friedrich Schiller University Jena, Dornburger Strasse 159, 07743 Jena, Germany
| | - Martin Taubert
- Aquatic Geomicrobiology, Institute of Biodiversity, Friedrich Schiller University Jena, Dornburger Strasse 159, 07743 Jena, Germany; Cluster of Excellence Balance of the Microverse, Friedrich Schiller University Jena, Grüne Aue, 07745 Jena, Germany
| | - Olga M Pérez-Carrascal
- Aquatic Geomicrobiology, Institute of Biodiversity, Friedrich Schiller University Jena, Dornburger Strasse 159, 07743 Jena, Germany; Cluster of Excellence Balance of the Microverse, Friedrich Schiller University Jena, Grüne Aue, 07745 Jena, Germany
| | - Robert Lehmann
- Hydrogeology, Institute of Geosciences, Friedrich Schiller University Jena, Burgweg 11, 07749 Jena, Germany
| | - Thomas Ritschel
- Hydrogeology, Institute of Geosciences, Friedrich Schiller University Jena, Burgweg 11, 07749 Jena, Germany
| | - Kai U Totsche
- Cluster of Excellence Balance of the Microverse, Friedrich Schiller University Jena, Grüne Aue, 07745 Jena, Germany; Hydrogeology, Institute of Geosciences, Friedrich Schiller University Jena, Burgweg 11, 07749 Jena, Germany
| | - Cassandre S Lazar
- Department of Biological Sciences, University of Quebec at Montreal, C.P. 8888, Succ. Centre-Ville, Montréal, QC H3C 3P8, Canada
| | - Kirsten Küsel
- Aquatic Geomicrobiology, Institute of Biodiversity, Friedrich Schiller University Jena, Dornburger Strasse 159, 07743 Jena, Germany; Cluster of Excellence Balance of the Microverse, Friedrich Schiller University Jena, Grüne Aue, 07745 Jena, Germany; German Center for Integrative Biodiversity Research (iDiv), Halle-Jena-Leipzig, Puschstrasse 4, 04103 Leipzig, Germany.
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