Rapid Freezing and Cryo-SEM-EDS Imaging of Foraminifera (Unicellular Eukaryotes) Using a Conductive Viscous Cryogenic Glue.
Microsc Microanal
; 30(2): 359-367, 2024 Apr 29.
Article
em En
| MEDLINE
| ID: mdl-38578298
ABSTRACT
Spatial distribution of water-soluble molecules and ions in living organisms is still challenging to assess. Energy-dispersive X-ray spectroscopy (EDS) via cryogenic scanning electron microscopy (cryo-SEM) is one of the promising methods to study them without loss of dissolved contents. High-resolution cryo-SEM-EDS has challenges in sample preparation, including cross-section exposure and sample drift/charging due to insulative surrounding water. The former becomes problematic for large and inseparable organisms, such as benthic foraminifera, a unicellular eukaryote playing significant roles in marine ecosystems, which often exceed the size limit for the most reliable high-pressure freezing. Here we show graphite oxide dispersed in sucrose solution as a good glue to freeze, expose cross-section by cryo-ultramicrotome, and analyze elemental distribution owing to the glue's high viscosity, adhesion force, and electron conductivity. To demonstrate the effectiveness and applicability of the glue for cryo-SEM-EDS, deep-sea foraminifer Uvigerina akitaensis was sampled during a cruise and plunge frozen directly on the research vessel, where the liquid nitrogen supply is limited. The microstructures were preserved as faithfully in cryo-SEM images as those with the conventional resin-substituted transmission electron micrograph. We found elements colocalized within the cytoplasm originating from water-soluble compounds that can be lost with conventional dehydrative fixation.
Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Espectrometria por Raios X
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Adesivos
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Microscopia Crioeletrônica
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Foraminíferos
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Congelamento
Idioma:
En
Revista:
Microsc Microanal
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Microsc. microanal
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Microscopy and microanalysis
Ano de publicação:
2024
Tipo de documento:
Article
País de afiliação:
Japão