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  • Frontiers Media SA  (7)
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Verlag/Herausgeber
  • Frontiers Media SA  (7)
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  • 1
    Online-Ressource
    Online-Ressource
    Frontiers Media SA ; 2018
    In:  Frontiers in Microbiology Vol. 9 ( 2018-4-25)
    In: Frontiers in Microbiology, Frontiers Media SA, Vol. 9 ( 2018-4-25)
    Materialart: Online-Ressource
    ISSN: 1664-302X
    Sprache: Unbekannt
    Verlag: Frontiers Media SA
    Publikationsdatum: 2018
    ZDB Id: 2587354-4
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Online-Ressource
    Online-Ressource
    Frontiers Media SA ; 2020
    In:  Frontiers in Earth Science Vol. 8 ( 2020-7-30)
    In: Frontiers in Earth Science, Frontiers Media SA, Vol. 8 ( 2020-7-30)
    Materialart: Online-Ressource
    ISSN: 2296-6463
    Sprache: Unbekannt
    Verlag: Frontiers Media SA
    Publikationsdatum: 2020
    ZDB Id: 2741235-0
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Online-Ressource
    Online-Ressource
    Frontiers Media SA ; 2023
    In:  Frontiers in Marine Science Vol. 10 ( 2023-5-26)
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 10 ( 2023-5-26)
    Kurzfassung: Coral reefs are known for being highly productive ecosystems in oligotrophic oceans, which is commonly referred to as the Darwin’s Paradox. Nitrogen is an essential component of organisms, but it limits primary productivity in most euphotic ocean, including the coral reef system. Therefore, understanding nitrogen’s transfer and transformation within the coral holobiont is essential to comprehend the holobiont homeostasis and functioning mechanisms, which may help to explain the Darwin’s Paradox. Previous studies have pointed out the fundamental importance of nitrogen cycling between coral host and symbiotic algae. Recently, increasing researches, particularly in quantitative aspect, have significantly improved our understandings of the various roles of nitrogen pathways in regulating the inter-relationship among coral host and symbiotic algae and the associated microbiome. In this paper, we synthesized knowledge advances of different nitrogen processes in coral holobionts standing on the nitrogen cycle perspective. We extracted consensus and contradictions from published research results regarding nitrogen flows of coral holobiont. This review presented the temporal and spatial variation of nitrogen fixation and analyzed the global nitrogen processes rates in coral holobionts. We also summarized projections of specific nitrogen processes of coral holobionts facing climate change from limited reports. We realized that there are significant gaps in our understanding of nitrogen processes in coral holobionts, which hindering our comprehension of nitrogen balance in coral holobionts and, therefore, the coral reef systems. These gaps include the roles and relative importance of nitrification, denitrification, and DNRA in coral holobionts, as well as the self-regulation mechanisms to maintain nitrogen-homeostasis in short-term and long-term, particularly in the context of environmental changes. At the end, we provide our opinions on research methods regarding quantitative coral research in the future.
    Materialart: Online-Ressource
    ISSN: 2296-7745
    Sprache: Unbekannt
    Verlag: Frontiers Media SA
    Publikationsdatum: 2023
    ZDB Id: 2757748-X
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    Online-Ressource
    Online-Ressource
    Frontiers Media SA ; 2022
    In:  Frontiers in Marine Science Vol. 9 ( 2022-12-16)
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 9 ( 2022-12-16)
    Kurzfassung: The supply of nitrogen (N) from various external and internal sources into the euphotic zone, e.g., atmospheric N deposition (AND), upwelling, lateral intrusion, and remineralization, modulates the biogeochemical and climatic roles of oligotrophic oceans and complicates N dynamics in the upper water column (≤200 m). However, our ability to resolve the mechanisms controlling upper-ocean N cycling is limited by the lack of high-resolution vertical observations. Here, we analyzed concentrations and dual isotopes of nitrate (NO 3 – ) in the upper 200 m of the oligotrophic South China Sea. By examining dual isotopic signatures of NO 3 – (δ 15 N NO3 and δ 18 O NO3 ) and multiple associated parameters vertically throughout the upper water column, we resolved the dominant N sources and processes, including AND/N 2 -fixation, assimilative fractionation, and nitrification, and quantitatively evaluated their contributions in the vertical distribution of NO 3 – , which can be separated into the Δδ 18 O NO3 -positive (δ 18 O NO3−obs −δ 18 O NO3−200m & gt;0) and Δδ 18 O NO3 -negative layers (δ 18 O NO3−obs −δ 18 O NO3−200m & lt;0) according to the deviation in δ 18 O NO3 at a given depth (δ 18 O NO3-obs ) from that at 200 m (δ 18 O NO3-200m ). In the Δδ 18 O NO3 -positive layer, the NO 3 – assimilated by phytoplankton was largely sourced from nitrification (39 ± 11%) and AND/N 2 fixation (17-28%), whereas these two processes accounted for 17 ± 10% and 7 ± 6% of the total NO 3 – pool in the Δδ 18 O NO3 -negative layer. Considering a substantial contribution of the regenerated (nitrification-sourced) NO 3 – to the total NO 3 – pool especially in the Δδ 18 O NO3 -positive layer, caution should be taken that the new production assessed by the rates of NO 3 – uptake may be significantly overestimated in the SCS. These findings not only highlight the importance of these biogeochemical processes to NO 3 – dynamics in the upper water column of marginal seas, but also with important implications for the estimation of biological carbon pump and/or the f -ratio.
    Materialart: Online-Ressource
    ISSN: 2296-7745
    Sprache: Unbekannt
    Verlag: Frontiers Media SA
    Publikationsdatum: 2022
    ZDB Id: 2757748-X
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    Online-Ressource
    Online-Ressource
    Frontiers Media SA ; 2021
    In:  Frontiers in Marine Science Vol. 8 ( 2021-8-2)
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 8 ( 2021-8-2)
    Kurzfassung: To distinguish between the distribution and activity of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in the Pearl River estuary (PRE), we investigated the DNA- and cDNA-based β-proteobacterial and archaeal amo A genes on three size-fractionated particles of & gt;3.0 μm, 0.45–3.0 μm, and 0.22–0.45 μm. Results showed that AOB were more abundant in the freshwater with high concentrations of ammonium (NH 4 + ) and low dissolved oxygen, whereas AOA were dominant in the NH 4 + -depleted seawater and sensitive to temperature. Obvious shifts in ammonia-oxidizing communities were found along the salinity gradient in the PRE. AOB clearly presented a particle-associated nature, as evidenced by higher relative abundance of amo A genes attached to the large particles ( & gt;3.0 μm) and their transcripts exclusively detected on this fraction. Moreover, higher transcriptional activity (indicated by the cDNA/DNA ratio) of AOB on the large particles, suggesting AOB were actively involved in ammonia oxidation despite their lower abundance in the mid- and lower estuarine regions. In contrast, AOA exhibited higher transcriptional activity on the 0.45–3.0 μm and 0.22–0.45 μm particles, implying the free-living strategy of these microbes. Together, these findings from field observations provide useful information on the ecological strategies of ammonia-oxidizing communities in response to different environmental conditions.
    Materialart: Online-Ressource
    ISSN: 2296-7745
    Sprache: Unbekannt
    Verlag: Frontiers Media SA
    Publikationsdatum: 2021
    ZDB Id: 2757748-X
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
    Online-Ressource
    Online-Ressource
    Frontiers Media SA ; 2022
    In:  Frontiers in Marine Science Vol. 9 ( 2022-12-12)
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 9 ( 2022-12-12)
    Kurzfassung: Estuaries channel large amounts of anthropogenic nitrogen (N) from continents to the offshore where productivity is widely limited by N and phosphorus. Ammonium and urea, two reduced forms of anthropogenic N commonly observed, are the preferred substrates for various microorganisms (e.g., uptake by phytoplankton or bacteria and oxidation by nitrifier). Yet, it remains underexplored how they transform and their concentrations vary during transport in the estuary which may influence the offshore microbial community. We applied 15 N isotope tracer incubation techniques to determine the two main bio-consumption processes, i.e., uptake and oxidation, of ammonium and urea, in the dark for the Jiulong River Estuary, a eutrophic estuary in southeastern China. Results showed that light penetration depth ranged from 0.8-3.3 m leaving 76% of estuary water bodies to stay in dark situations throughout a day. Ammonia oxidation, which favors dark conditions, dominates the estuarine regenerated-N cycle, showing the rank: ammonia oxidation & gt; ammonium uptake & gt; & gt; urea uptake ≈ urea oxidation. By compiling the reported case studies, we found the relatively low ratio of urea oxidation to ammonia oxidation was accompanied by a relatively high ammonium concentration. Microorganisms’ high preference for ammonium over urea may lead to an inhibitory-like phenomenon. An analogous effect was evident by the increased urea uptake at downstream when ammonium was down to a few µM. The obstructed urea utilization resulted in 10 times longer lifetime for urea relative to ammonium (surface: 19 ± 9 days; bottom 12 ± 7 days). Such an inhibitory-like effect allows urea to be preserved in the estuary and allows urea to be transported farther offshore to stimulate microorganisms capable of utilizing urea, which may have significant impacts on offshore ecology.
    Materialart: Online-Ressource
    ISSN: 2296-7745
    Sprache: Unbekannt
    Verlag: Frontiers Media SA
    Publikationsdatum: 2022
    ZDB Id: 2757748-X
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 7
    Online-Ressource
    Online-Ressource
    Frontiers Media SA ; 2023
    In:  Frontiers in Microbiology Vol. 14 ( 2023-4-20)
    In: Frontiers in Microbiology, Frontiers Media SA, Vol. 14 ( 2023-4-20)
    Kurzfassung: Green sulfur bacteria (GSB) are a distinct group of anoxygenic phototrophic bacteria that are found in many ecological niches. Prosthecochloris , a marine representative genus of GSB, was found to be dominant in some coral skeletons. However, how coral-associated Prosthecochloris (CAP) adapts to diurnal changing microenvironments in coral skeletons is still poorly understood. In this study, three Prosthecochloris genomes were obtained through enrichment culture from the skeleton of the stony coral Galaxea fascicularis . These divergent three genomes belonged to Prosthecochloris marina and two genomes were circular. Comparative genomic analysis showed that between the CAP and non-CAP clades, CAP genomes possess specialized metabolic capacities (CO oxidation, CO 2 hydration and sulfur oxidation), gas vesicles (vertical migration in coral skeletons), and cbb 3 -type cytochrome c oxidases (oxygen tolerance and gene regulation) to adapt to the microenvironments of coral skeletons. Within the CAP clade, variable polysaccharide synthesis gene clusters and phage defense systems may endow bacteria with differential cell surface structures and phage susceptibility, driving strain-level evolution. Furthermore, mobile genetic elements (MGEs) or evidence of horizontal gene transfer (HGT) were found in most of the genomic loci containing the above genes, suggesting that MGEs play an important role in the evolutionary diversification between CAP and non-CAP strains and within CAP clade strains. Our results provide insight into the adaptive strategy and population evolution of endolithic Prosthecochloris strains in coral skeletons.
    Materialart: Online-Ressource
    ISSN: 1664-302X
    Sprache: Unbekannt
    Verlag: Frontiers Media SA
    Publikationsdatum: 2023
    ZDB Id: 2587354-4
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
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