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  • 1
    In: Earth Science, Systems and Society, Frontiers Media SA, Vol. 2 ( 2022-6-23)
    Abstract: In 1964, exploration drilling in the German Sector of the North Sea hit a gas pocket at ∼2900 m depth below the seafloor and triggered a blowout, which formed a 550 m-wide and up to 38 m deep seafloor crater now known as Figge Maar. Although seafloor craters formed by fluid flow are very common structures, little is known about their formation dynamics. Here, we present 2D reflection seismic, sediment echosounder, and multibeam echosounder data from three geoscientific surveys of the Figge Maar blowout crater, which are used to reconstruct its formation. Reflection seismic data support a scenario in which overpressured gas ascended first through the lower part of the borehole and then migrated along steeply inclined strata and faults towards the seafloor. The focused discharge of gas at the seafloor removed up to 4.8 Mt of sediments in the following weeks of vigorous venting. Eyewitness accounts document that the initial phase of crater formation was characterized by the eruptive expulsion of fluids and sediments cutting deep into the substrate. This was followed by a prolonged phase of sediment fluidization and redistribution widening the crater. After fluid discharge ceased, the Figge Maar acted as a sediment trap reducing the crater depth to ∼12 m relative to the surrounding seafloor in 2018, which corresponds to an average sedimentation rate of ∼22,000 m 3 /yr between 1995 and 2018. Hydroacoustic and geochemical data indicate that the Figge Maar nowadays emits primarily biogenic methane, predominantly during low tide. The formation of Figge Maar illustrates hazards related to the formation of secondary fluid pathways, which can bypass safety measures at the wellhead and are thus difficult to control.
    Type of Medium: Online Resource
    ISSN: 2634-730X
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2022
    detail.hit.zdb_id: 3106190-4
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  • 2
    Online Resource
    Online Resource
    Frontiers Media SA ; 2021
    In:  Frontiers in Immunology Vol. 12 ( 2021-3-22)
    In: Frontiers in Immunology, Frontiers Media SA, Vol. 12 ( 2021-3-22)
    Abstract: Although the crucial role of professional phagocytes for the clearance of S. aureus infections is well-established, several studies indicate an adverse role of leukocytes in the dissemination of S. aureus during infection. Since only little is known about macrophages in this context, we analyzed the role of macrophages, and in particular reactive oxygen species deficiency, for the seeding of S. aureus metastases. Infection of bone marrow-derived macrophages (BMDM) with S. aureus revealed that NADPH oxidase 2 (NOX2-) deficient, but not NOX1- or NOX4-deficient, BMDM failed to clear intracellular S. aureus . Despite of larger intracellular bacterial burden, NOX2-deficient BMDM showed significantly improved survival. Intravenous injection of mice with in vitro -infected BMDMs carrying intracellular viable S. aureus led to higher bacterial loads in kidney and liver of mice compared to injection with plain S. aureus . An even higher frequency of liver abscesses was observed in mice infected with S. aureus -loaded nox2 −/− BMDM. Thus, the improved intracellular survival of S. aureus and improved viability of NOX2-deficient BMDM is associated with an aggravated metastatic dissemination of S. aureus infection. A combination of vancomycin and the intracellularly active antibiotic rifampicin led to complete elimination of S. aureus from liver within 48 h, which was not achieved with vancomycin treatment alone, underscoring the impact of intracellular S. aureus on the course of disease. The results of our study indicate that intracellular S. aureus carried by macrophages are sufficient to establish a systemic infection. This suggests the inclusion of intracellularly active antibiotics in the therapeutic regimen of invasive S. aureus infections, especially in patients with NADPH oxidase deficiencies such as chronic granulomatous disease.
    Type of Medium: Online Resource
    ISSN: 1664-3224
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
    detail.hit.zdb_id: 2606827-8
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