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Saona LA, Villafañe PG, Carrizo D, Cónsole Gonella C, Néspolo RF, Farías ME. Geomicrobiological characterization of the evaporitic ecosystem in the hypersaline lake Laguna Verde (Andean Puna, Northwestern Argentina). Ecol Evol 2024; 14:e10931. [PMID: 38348017 PMCID: PMC10859677 DOI: 10.1002/ece3.10931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 12/04/2023] [Accepted: 01/02/2024] [Indexed: 02/15/2024] Open
Abstract
Laguna Verde's dome-shaped structures are distinctive formations within the Central Andes, displaying unique geomicrobiological features. This study represents a pioneering investigation into these structures, assessing their formation, associated taxa, and ecological significance. Through a multifaceted approach that includes chemical analysis of the water body, multiscale characterization of the domes, and analysis of the associated microorganisms, we reveal the complex interplay between geology and biology in this extreme environment. The lake's alkaline waters that are rich in dissolved cations and anions such as chloride, sodium sulfate, and potassium, coupled with its location at the margin of the Antofalla salt flat, fed by alluvial fans and hydrothermal input, provide favorable conditions for mineral precipitation and support for the microorganism's activity. Laguna Verde's dome-shaped structures are mainly composed of gypsum and halite, displaying an internal heterogeneous mesostructure consisting of three zones: microcrystalline, organic (orange and green layers), and crystalline. The green layer of the organic zone is predominantly composed of Proteobacteria, Bacteroidetes, and Cyanobacteria, while the orange layer is mostly inhabited by Cyanobacteria. The results of the study suggest that oxygenic photosynthesis performed by Cyanobacteria is the main carbon fixation pathway in the microbial community, supported by carbon isotopic ratios of specific biomarkers. This finding highlights the important role played by Cyanobacteria in this ecosystem.
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Affiliation(s)
- L. A. Saona
- Facultad de Química y BiologíaUniversidad de Santiago de Chile (USACH)SantiagoChile
- Millennium Nucleus of Patagonian Limit of Life (LiLi)ValdiviaChile
- Millennium Institute for Integrative Biology (iBio)SantiagoChile
| | - P. G. Villafañe
- Instituto Superior de Correlación Geológica (INSUGEO), CONICET‐UNTTucumánArgentina
- GIUV2016‐303, Department of Botany and GeologyUniversitat de ValènciaValènciaEspaña
| | - D. Carrizo
- Centro de AstrobiologíaInstituto Nacional de Técnica AeroespacialMadridEspaña
| | - C. Cónsole Gonella
- Instituto Superior de Correlación Geológica (INSUGEO), CONICET‐UNTTucumánArgentina
| | - R. F. Néspolo
- Millennium Nucleus of Patagonian Limit of Life (LiLi)ValdiviaChile
- Millennium Institute for Integrative Biology (iBio)SantiagoChile
- Instituto de Ciencias Ambientales y EvolutivasUniversidad Austral de ChileValdiviaChile
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Grim SL, Stuart DG, Aron P, Levin NE, Kinsman-Costello L, Waldbauer JR, Dick GJ. Seasonal shifts in community composition and proteome expression in a sulphur-cycling cyanobacterial mat. Environ Microbiol 2023; 25:2516-2533. [PMID: 37596970 DOI: 10.1111/1462-2920.16480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 07/29/2023] [Indexed: 08/21/2023]
Abstract
Seasonal changes in light and physicochemical conditions have strong impacts on cyanobacteria, but how they affect community structure, metabolism, and biogeochemistry of cyanobacterial mats remains unclear. Light may be particularly influential for cyanobacterial mats exposed to sulphide by altering the balance of oxygenic photosynthesis and sulphide-driven anoxygenic photosynthesis. We studied temporal shifts in irradiance, water chemistry, and community structure and function of microbial mats in the Middle Island Sinkhole (MIS), where anoxic and sulphate-rich groundwater provides habitat for cyanobacteria that conduct both oxygenic and anoxygenic photosynthesis. Seasonal changes in light and groundwater chemistry were accompanied by shifts in bacterial community composition, with a succession of dominant cyanobacteria from Phormidium to Planktothrix, and an increase in diatoms, sulphur-oxidizing bacteria, and sulphate-reducing bacteria from summer to autumn. Differential abundance of cyanobacterial light-harvesting proteins likely reflects a physiological response of cyanobacteria to light level. Beggiatoa sulphur oxidation proteins were more abundant in autumn. Correlated abundances of taxa through time suggest interactions between sulphur oxidizers and sulphate reducers, sulphate reducers and heterotrophs, and cyanobacteria and heterotrophs. These results support the conclusion that seasonal change, including light availability, has a strong influence on community composition and biogeochemical cycling of sulphur and O2 in cyanobacterial mats.
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Affiliation(s)
- Sharon L Grim
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan, USA
| | - Dack G Stuart
- Cooperative Institute for Great Lakes Research, University of Michigan, Ann Arbor, Michigan, USA
| | - Phoebe Aron
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan, USA
| | - Naomi E Levin
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan, USA
| | | | - Jacob R Waldbauer
- Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois, USA
| | - Gregory J Dick
- Department of Earth and Environmental Sciences, Cooperative Institute for Great Lakes Research, University of Michigan, Ann Arbor, Michigan, USA
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Gonzalez-Nayeck AC, Grim SL, Waldbauer J, Dick GJ, Pearson A. Isotopic Signatures of Carbon Transfer in a Proterozoic Analogue Microbial Mat. Appl Environ Microbiol 2023; 89:e0187022. [PMID: 37093010 PMCID: PMC10231192 DOI: 10.1128/aem.01870-22] [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: 11/04/2022] [Accepted: 03/24/2023] [Indexed: 04/25/2023] Open
Abstract
Modern microbial mats are potential analogues for Proterozoic ecosystems, yet only a few studies have characterized mats under low-oxygen conditions that are relevant to Proterozoic environments. Here, we use protein-stable isotope fingerprinting (P-SIF) to determine the protein carbon isotope (δ13C) values of autotrophic, heterotrophic, and mixotrophic organisms in a benthic microbial mat from the low-oxygen Middle Island Sinkhole, Lake Huron, USA (MIS). We also measure the δ13C values of the sugar moieties of exopolysaccharides (EPS) within the mat to explore the relationships between cyanobacterial exudates and heterotrophic anabolic carbon uptake. Our results show that Cyanobacteria (autotrophs) are 13C-depleted, relative to sulfate-reducing bacteria (heterotrophs), and 13C-enriched, relative to sulfur oxidizing bacteria (autotrophs or mixotrophs). We also find that the pentose moieties of EPS are systematically enriched in 13C, relative to the hexose moieties of EPS. We hypothesize that these isotopic patterns reflect cyanobacterial metabolic pathways, particularly phosphoketolase, that are relatively more active in low-oxygen mat environments, rather than oxygenated mat environments. This results in isotopically more heterogeneous C sources in low-oxygen mats. While this might partially explain the isotopic variability observed in Proterozoic mat facies, further work is necessary to systematically characterize the isotopic fractionations that are associated with the synthesis of cyanobacterial exudates. IMPORTANCE The δ13C compositions of heterotrophic microorganisms are dictated by the δ13C compositions of their organic carbon sources. In both modern and ancient photosynthetic microbial mats, photosynthetic exudates are the most likely source of organic carbon for heterotrophs. We measured the δ13C values of autotrophic, heterotrophic, and mixotrophic bacteria as well as the δ13C value of the most abundant photosynthetic exudate (exopolysaccharide) in a modern analogue for a Proterozoic environment. Given these data, future studies will be better equipped to estimate the most likely carbon source for heterotrophs in both modern environments as well as in Proterozoic environments preserved in the rock record.
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Affiliation(s)
- Ana C. Gonzalez-Nayeck
- Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA
| | - Sharon L. Grim
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan, USA
| | - Jacob Waldbauer
- Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois, USA
| | - Gregory J. Dick
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan, USA
| | - Ann Pearson
- Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA
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The Transcriptional Repressor PerR Senses Sulfane Sulfur by Cysteine Persulfidation at the Structural Zn 2+ Site in Synechococcus sp. PCC7002. Antioxidants (Basel) 2023; 12:antiox12020423. [PMID: 36829981 PMCID: PMC9952342 DOI: 10.3390/antiox12020423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 02/03/2023] [Accepted: 02/07/2023] [Indexed: 02/11/2023] Open
Abstract
Cyanobacteria can perform both anoxygenic and oxygenic photosynthesis, a characteristic which ensured that these organisms were crucial in the evolution of the early Earth and the biosphere. Reactive oxygen species (ROS) produced in oxygenic photosynthesis and reactive sulfur species (RSS) produced in anoxygenic photosynthesis are closely related to intracellular redox equilibrium. ROS comprise superoxide anion (O2●-), hydrogen peroxide (H2O2), and hydroxyl radicals (●OH). RSS comprise H2S and sulfane sulfur (persulfide, polysulfide, and S8). Although the sensing mechanism for ROS in cyanobacteria has been explored, that of RSS has not been elucidated. Here, we studied the function of the transcriptional repressor PerR in RSS sensing in Synechococcus sp. PCC7002 (PCC7002). PerR was previously reported to sense ROS; however, our results revealed that it also participated in RSS sensing. PerR repressed the expression of prxI and downregulated the tolerance of PCC7002 to polysulfide (H2Sn). The reporter system indicated that PerR sensed H2Sn. Cys121 of the Cys4:Zn2+ site, which contains four cysteines (Cys121, Cys124, Cys160, and Cys163) bound to one zinc atom, could be modified by H2Sn to Cys121-SSH, as a result of which the zinc atom was released from the site. Moreover, Cys19 could also be modified by polysulfide to Cys19-SSH. Thus, our results reveal that PerR, a representative of the Cys4 zinc finger proteins, senses H2Sn. Our findings provide a new perspective to explore the adaptation strategy of cyanobacteria in Proterozoic and contemporary sulfurization oceans.
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Aronson HS, Monteverde DR, Barnes BD, Johnson BR, Zawaski MJ, Speth DR, Wang XT, Wu F, Webb SM, Trower EJ, Magyar JS, Sessions AL, Orphan VJ, Fischer WW. Sulfur cycling at natural hydrocarbon and sulfur seeps in Santa Paula Creek, CA. GEOBIOLOGY 2022; 20:707-725. [PMID: 35894090 DOI: 10.1111/gbi.12512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 05/31/2022] [Accepted: 06/26/2022] [Indexed: 06/15/2023]
Abstract
Biogeochemical cycling of sulfur is relatively understudied in terrestrial environments compared to marine environments. However, the comparative ease of access, observation, and sampling of terrestrial settings can expand our understanding of organisms and processes important in the modern sulfur cycle. Furthermore, these sites may allow for the discovery of useful process analogs for ancient sulfur-metabolizing microbial communities at times in Earth's past when atmospheric O2 concentrations were lower and sulfide was more prevalent in Earth surface environments. We identified a new site at Santa Paula Creek (SPC) in Ventura County, CA-a remarkable freshwater, gravel-bedded mountain stream charged with a range of oxidized and reduced sulfur species and heavy hydrocarbons from the emergence of subsurface fluids within the underlying sulfur- and organic-rich Miocene-age Monterey Formation. SPC hosts a suite of morphologically distinct microbial biofacies that form in association with the naturally occurring hydrocarbon seeps and sulfur springs. We characterized the geology, stream geochemistry, and microbial facies and diversity of the Santa Paula Creek ecosystem. Using geochemical analyses and 16S rRNA gene sequencing, we found that SPC supports a dynamic sulfur cycle that is largely driven by sulfide-oxidizing microbial taxa, with contributions from smaller populations of sulfate-reducing and sulfur-disproportionating taxa. This preliminary characterization of SPC revealed an intriguing site in which to study geological and geochemical controls on microbial community composition and to expand our understanding of sulfur cycling in terrestrial environments.
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Affiliation(s)
- Heidi S Aronson
- Department of Biological Sciences, University of Southern California, Los Angeles, California, USA
| | - Danielle R Monteverde
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
| | - Ben Davis Barnes
- Department of Geosciences, Pennsylvania State University, Pennsylvania, USA
| | - Brooke R Johnson
- Early Life Traces & Evolution-Astrobiology, University of Liège, Liège, Belgium
- Department of Earth Sciences, Oxford University, Oxford, UK
| | - Mike J Zawaski
- Department of Geological Sciences, University of Colorado Boulder, Boulder, Colorado, USA
| | - Daan R Speth
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA
| | - Xingchen Tony Wang
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
- Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, Massachusetts, USA
| | - Fenfang Wu
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
| | - Samuel M Webb
- SLAC National Accelerator Laboratory, Stanford Synchrotron Radiation Lightsource, Menlo Park, California, USA
| | | | - John S Magyar
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
| | - Alex L Sessions
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
| | - Victoria J Orphan
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA
| | - Woodward W Fischer
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
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Gorbunov MY, Khlopko YA, Kataev VY, Umanskaya MV. Bacterial Diversity in Attached Communities of a Cold High-Sulfide Water Body in European Russia. Microbiology (Reading) 2022. [DOI: 10.1134/s0026261722010040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Omics-Inferred Partitioning and Expression of Diverse Biogeochemical Functions in a Low-O 2 Cyanobacterial Mat Community. mSystems 2021; 6:e0104221. [PMID: 34874776 PMCID: PMC8651085 DOI: 10.1128/msystems.01042-21] [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] [Indexed: 11/20/2022] Open
Abstract
Cyanobacterial mats profoundly influenced Earth’s biological and geochemical evolution and still play important ecological roles in the modern world. However, the biogeochemical functioning of cyanobacterial mats under persistent low-O2 conditions, which dominated their evolutionary history, is not well understood. To investigate how different metabolic and biogeochemical functions are partitioned among community members, we conducted metagenomics and metatranscriptomics on cyanobacterial mats in the low-O2, sulfidic Middle Island sinkhole (MIS) in Lake Huron. Metagenomic assembly and binning yielded 144 draft metagenome assembled genomes, including 61 of medium quality or better, and the dominant cyanobacteria and numerous Proteobacteria involved in sulfur cycling. Strains of a Phormidium autumnale-like cyanobacterium dominated the metagenome and metatranscriptome. Transcripts for the photosynthetic reaction core genes psaA and psbA were abundant in both day and night. Multiple types of psbA genes were expressed from each cyanobacterium, and the dominant psbA transcripts were from an atypical microaerobic type of D1 protein from Phormidium. Further, cyanobacterial transcripts for photosystem I genes were more abundant than those for photosystem II, and two types of Phormidium sulfide quinone reductase were recovered, consistent with anoxygenic photosynthesis via photosystem I in the presence of sulfide. Transcripts indicate active sulfur oxidation and reduction within the cyanobacterial mat, predominately by Gammaproteobacteria and Deltaproteobacteria, respectively. Overall, these genomic and transcriptomic results link specific microbial groups to metabolic processes that underpin primary production and biogeochemical cycling in a low-O2 cyanobacterial mat and suggest mechanisms for tightly coupled cycling of oxygen and sulfur compounds in the mat ecosystem. IMPORTANCE Cyanobacterial mats are dense communities of microorganisms that contain photosynthetic cyanobacteria along with a host of other bacterial species that play important yet still poorly understood roles in this ecosystem. Although such cyanobacterial mats were critical agents of Earth’s biological and chemical evolution through geological time, little is known about how they function under the low-oxygen conditions that characterized most of their natural history. Here, we performed sequencing of the DNA and RNA of modern cyanobacterial mat communities under low-oxygen and sulfur-rich conditions from the Middle Island sinkhole in Lake Huron. The results reveal the organisms and metabolic pathways that are responsible for both oxygen-producing and non-oxygen-producing photosynthesis as well as interconversions of sulfur that likely shape how much O2 is produced in such ecosystems. These findings indicate tight metabolic reactions between community members that help to explain the limited the amount of O2 produced in cyanobacterial mat ecosystems.
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Nandagopal P, Steven AN, Chan LW, Rahmat Z, Jamaluddin H, Mohd Noh NI. Bioactive Metabolites Produced by Cyanobacteria for Growth Adaptation and Their Pharmacological Properties. BIOLOGY 2021; 10:1061. [PMID: 34681158 PMCID: PMC8533319 DOI: 10.3390/biology10101061] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 10/10/2021] [Accepted: 10/14/2021] [Indexed: 02/08/2023]
Abstract
Cyanobacteria are the most abundant oxygenic photosynthetic organisms inhabiting various ecosystems on earth. As with all other photosynthetic organisms, cyanobacteria release oxygen as a byproduct during photosynthesis. In fact, some cyanobacterial species are involved in the global nitrogen cycles by fixing atmospheric nitrogen. Environmental factors influence the dynamic, physiological characteristics, and metabolic profiles of cyanobacteria, which results in their great adaptation ability to survive in diverse ecosystems. The evolution of these primitive bacteria resulted from the unique settings of photosynthetic machineries and the production of bioactive compounds. Specifically, bioactive compounds play roles as regulators to provide protection against extrinsic factors and act as intracellular signaling molecules to promote colonization. In addition to the roles of bioactive metabolites as indole alkaloids, terpenoids, mycosporine-like amino acids, non-ribosomal peptides, polyketides, ribosomal peptides, phenolic acid, flavonoids, vitamins, and antimetabolites for cyanobacterial survival in numerous habitats, which is the focus of this review, the bioactivities of these compounds for the treatment of various diseases are also discussed.
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Affiliation(s)
- Pavitra Nandagopal
- Department of Biosciences, Faculty of Science, Universiti Teknologi Malaysia, Skudai 81310, Malaysia; (P.N.); (L.-W.C.); (Z.R.); (H.J.)
| | - Anthony Nyangson Steven
- Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, Skudai 81310, Malaysia;
| | - Liong-Wai Chan
- Department of Biosciences, Faculty of Science, Universiti Teknologi Malaysia, Skudai 81310, Malaysia; (P.N.); (L.-W.C.); (Z.R.); (H.J.)
| | - Zaidah Rahmat
- Department of Biosciences, Faculty of Science, Universiti Teknologi Malaysia, Skudai 81310, Malaysia; (P.N.); (L.-W.C.); (Z.R.); (H.J.)
- Institute of Bioproduct Development, Universiti Teknologi Malaysia, Skudai 81310, Malaysia
| | - Haryati Jamaluddin
- Department of Biosciences, Faculty of Science, Universiti Teknologi Malaysia, Skudai 81310, Malaysia; (P.N.); (L.-W.C.); (Z.R.); (H.J.)
| | - Nur Izzati Mohd Noh
- Department of Biosciences, Faculty of Science, Universiti Teknologi Malaysia, Skudai 81310, Malaysia; (P.N.); (L.-W.C.); (Z.R.); (H.J.)
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Block KR, O'Brien JM, Edwards WJ, Marnocha CL. Vertical structure of the bacterial diversity in meromictic Fayetteville Green Lake. Microbiologyopen 2021; 10:e1228. [PMID: 34459548 PMCID: PMC8330806 DOI: 10.1002/mbo3.1228] [Citation(s) in RCA: 6] [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: 04/15/2021] [Revised: 07/16/2021] [Accepted: 07/19/2021] [Indexed: 11/08/2022] Open
Abstract
The permanently stratified water columns in euxinic meromictic lakes produce niche environments for phototrophic sulfur oxidizers and diverse sulfur metabolisms. While Green Lake (Fayetteville, New York, NY) is known to host a diverse community of ecologically important sulfur bacteria, analyses of its microbial communities, to date, have been largely based on pigment analysis and smaller datasets from Sanger sequencing techniques. Here, we present the results of next-generation sequencing of the eubacterial community in the context of the water column geochemistry. We observed abundant purple and green sulfur bacteria, as well as anoxygenic photosynthesis-capable cyanobacteria within the upper monimolimnion. Amidst the phototrophs, we found other sulfur-cycling bacteria including sulfur disproportionators and chemotrophic sulfur oxidizers, further detailing our understanding of the sulfur cycle and microbial ecology of euxinic, meromictic lakes.
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Affiliation(s)
| | - Joy M. O'Brien
- Department of BiologyNiagara UniversityLewistonNew YorkUSA
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Merz E, Dick GJ, de Beer D, Grim S, Hübener T, Littmann S, Olsen K, Stuart D, Lavik G, Marchant HK, Klatt JM. Nitrate respiration and diel migration patterns of diatoms are linked in sediments underneath a microbial mat. Environ Microbiol 2020; 23:1422-1435. [PMID: 33264477 DOI: 10.1111/1462-2920.15345] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/23/2020] [Accepted: 11/30/2020] [Indexed: 12/12/2022]
Abstract
Diatoms are among the few eukaryotes known to store nitrate (NO3 - ) and to use it as an electron acceptor for respiration in the absence of light and O2 . Using microscopy and 15 N stable isotope incubations, we studied the relationship between dissimilatory nitrate/nitrite reduction to ammonium (DNRA) and diel vertical migration of diatoms in phototrophic microbial mats and the underlying sediment of a sinkhole in Lake Huron (USA). We found that the diatoms rapidly accumulated NO3 - at the mat-water interface in the afternoon and 40% of the population migrated deep into the sediment, where they were exposed to dark and anoxic conditions for ~75% of the day. The vertical distribution of DNRA rates and diatom abundance maxima coincided, suggesting that DNRA was the main energy generating metabolism of the diatom population. We conclude that the illuminated redox-dynamic ecosystem selects for migratory diatoms that can store nitrate for respiration in the absence of light. A major implication of this study is that the dominance of DNRA over denitrification is not explained by kinetics or thermodynamics. Rather, the dynamic conditions select for migratory diatoms that perform DNRA and can outcompete sessile denitrifiers.
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Affiliation(s)
- Elisa Merz
- Max Planck Institute for Marine Microbiology, Celsiusstr. 1, Bremen, Germany
| | - Gregory J Dick
- Geomicrobiology Lab, Department of Earth & Environmental Sciences, University of Michigan, Ann Arbor, Michigan, USA
| | - Dirk de Beer
- Max Planck Institute for Marine Microbiology, Celsiusstr. 1, Bremen, Germany
| | - Sharon Grim
- Geomicrobiology Lab, Department of Earth & Environmental Sciences, University of Michigan, Ann Arbor, Michigan, USA
| | - Thomas Hübener
- Department of Botany and Botanical Garden, University of Rostock, Institute of Biosciences, Germany
| | - Sten Littmann
- Max Planck Institute for Marine Microbiology, Celsiusstr. 1, Bremen, Germany
| | - Kirk Olsen
- Geomicrobiology Lab, Department of Earth & Environmental Sciences, University of Michigan, Ann Arbor, Michigan, USA
| | - Dack Stuart
- University of Michigan, Cooperative Institute for Great Lakes Research, Ann Arbor, Michigan, USA
| | - Gaute Lavik
- Max Planck Institute for Marine Microbiology, Celsiusstr. 1, Bremen, Germany
| | - Hannah K Marchant
- Max Planck Institute for Marine Microbiology, Celsiusstr. 1, Bremen, Germany
| | - Judith M Klatt
- Max Planck Institute for Marine Microbiology, Celsiusstr. 1, Bremen, Germany.,Geomicrobiology Lab, Department of Earth & Environmental Sciences, University of Michigan, Ann Arbor, Michigan, USA
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