Microbial carbon oxidation in seawater below the hypoxic threshold
Abstract Global oxygen minimum zones (OMZs) often reach hypoxia but seldom reach anoxia. Recently it was reported that Michaelis Menten constants (Km) of oxidative enzymes are orders of magnitude higher than respiratory Km values, and in the Hypoxic Barrier Hypothesis it was proposed that, in ecosys...
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Nature Portfolio
2025-01-01
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| Series: | Scientific Reports |
| Online Access: | https://doi.org/10.1038/s41598-024-82438-z |
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| author | Sarah Wolf Clare Jayawickrama Craig A. Carlson Curtis Deutsch Edward W. Davis Benjamin N. Daniels Francis Chan Stephen J. Giovannoni |
| author_facet | Sarah Wolf Clare Jayawickrama Craig A. Carlson Curtis Deutsch Edward W. Davis Benjamin N. Daniels Francis Chan Stephen J. Giovannoni |
| author_sort | Sarah Wolf |
| collection | DOAJ |
| description | Abstract Global oxygen minimum zones (OMZs) often reach hypoxia but seldom reach anoxia. Recently it was reported that Michaelis Menten constants (Km) of oxidative enzymes are orders of magnitude higher than respiratory Km values, and in the Hypoxic Barrier Hypothesis it was proposed that, in ecosystems experiencing falling oxygen, oxygenase enzyme activities become oxygen-limited long before respiration. We conducted a mesocosm experiment with a phytoplankton bloom as an organic carbon source and controlled dissolved oxygen (DO) concentrations in the dark to determine whether hypoxia slows carbon oxidation and oxygen decline. Total oxygen utilization (TOU) in hypoxic treatment (ca. 7.1 µM O2) was 21.7% lower than the oxic treatment (ca. 245.1 µM O2) over the first 43 days of the experiment. In addition, following the restoration of fully oxic conditions to the hypoxic treatment, TOU accelerated, demonstrating that oxidative processes are sensitive to DO concentrations found in large volumes of the ocean. Microbial amplicon-based community composition diverged between oxic treatments, indicating a specialized microbiome that included Thioglobaceae (SUP05 Gammaproteobacteria), OM190 (Planctomycetota), ABY1 (Patescibacteria), and SAR86 subclade D2472, thrived in the hypoxic treatment, while the genus Candidatus Actinomarina and SAR11 alphaproteobacteria were sharply inhibited. Our findings support the hypothesis that oxygenase kinetics might slow the progression of ocean deoxygenation in oxygen-poor regions and be a factor in the evolution of microbial taxa adapted to hypoxic environments. |
| format | Article |
| id | doaj-art-b1bf525a518c4d929201fab1d9f43336 |
| institution | Kabale University |
| issn | 2045-2322 |
| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-b1bf525a518c4d929201fab1d9f433362025-01-26T12:25:40ZengNature PortfolioScientific Reports2045-23222025-01-0115111410.1038/s41598-024-82438-zMicrobial carbon oxidation in seawater below the hypoxic thresholdSarah Wolf0Clare Jayawickrama1Craig A. Carlson2Curtis Deutsch3Edward W. Davis4Benjamin N. Daniels5Francis Chan6Stephen J. Giovannoni7Department of Microbiology, Oregon State UniversityDepartment of Microbiology, Oregon State UniversityMarine Science Institute, UC Santa BarbaraDepartment of Geosciences, Princeton UniversityCenter for Quantitative Life Sciences, Oregon State UniversityDepartment of Microbiology, Oregon State UniversityDepartment of Integrative Biology, Oregon State UniversityDepartment of Microbiology, Oregon State UniversityAbstract Global oxygen minimum zones (OMZs) often reach hypoxia but seldom reach anoxia. Recently it was reported that Michaelis Menten constants (Km) of oxidative enzymes are orders of magnitude higher than respiratory Km values, and in the Hypoxic Barrier Hypothesis it was proposed that, in ecosystems experiencing falling oxygen, oxygenase enzyme activities become oxygen-limited long before respiration. We conducted a mesocosm experiment with a phytoplankton bloom as an organic carbon source and controlled dissolved oxygen (DO) concentrations in the dark to determine whether hypoxia slows carbon oxidation and oxygen decline. Total oxygen utilization (TOU) in hypoxic treatment (ca. 7.1 µM O2) was 21.7% lower than the oxic treatment (ca. 245.1 µM O2) over the first 43 days of the experiment. In addition, following the restoration of fully oxic conditions to the hypoxic treatment, TOU accelerated, demonstrating that oxidative processes are sensitive to DO concentrations found in large volumes of the ocean. Microbial amplicon-based community composition diverged between oxic treatments, indicating a specialized microbiome that included Thioglobaceae (SUP05 Gammaproteobacteria), OM190 (Planctomycetota), ABY1 (Patescibacteria), and SAR86 subclade D2472, thrived in the hypoxic treatment, while the genus Candidatus Actinomarina and SAR11 alphaproteobacteria were sharply inhibited. Our findings support the hypothesis that oxygenase kinetics might slow the progression of ocean deoxygenation in oxygen-poor regions and be a factor in the evolution of microbial taxa adapted to hypoxic environments.https://doi.org/10.1038/s41598-024-82438-z |
| spellingShingle | Sarah Wolf Clare Jayawickrama Craig A. Carlson Curtis Deutsch Edward W. Davis Benjamin N. Daniels Francis Chan Stephen J. Giovannoni Microbial carbon oxidation in seawater below the hypoxic threshold Scientific Reports |
| title | Microbial carbon oxidation in seawater below the hypoxic threshold |
| title_full | Microbial carbon oxidation in seawater below the hypoxic threshold |
| title_fullStr | Microbial carbon oxidation in seawater below the hypoxic threshold |
| title_full_unstemmed | Microbial carbon oxidation in seawater below the hypoxic threshold |
| title_short | Microbial carbon oxidation in seawater below the hypoxic threshold |
| title_sort | microbial carbon oxidation in seawater below the hypoxic threshold |
| url | https://doi.org/10.1038/s41598-024-82438-z |
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