Compositional contrast of uncoated fungal spores and stained section-face by low-loss backscattered electron imaging. 2009

Ki Woo Kim, and Heiner Jaksch
National Instrumentation Center for Environmental Management, Seoul National University, Seoul 151-921, Republic of Korea. kiwoo@snu.ac.kr

Comparative surface imaging was performed on uncoated fungal spores and stained section-face by field emission scanning electron microscopy with an in-column energy-selective backscattered electron detector. Epoxy resin thin sections (ca. 200 and 500 nm thick) of the osmicated and uranyl acetate/lead citrate-stained fungus were examined with the microscope. Topographical contrast was evident in secondary electron imaging by either a below-lens or an in-lens detector. Meanwhile, low-loss backscattered electron images showed mainly compositional contrast at low accelerating voltages (mostly below 1 kV). With attenuated topographical contrast, several different electron densities could be detected, exhibiting several levels of electron density even on a flat plane of spines. Minute differences in topography on epoxy resin sections as seen by secondary electron imaging represented the periphery of the fungal spores and hyphae. On the other hand, the compositional contrast could be retrieved from stained section-face in low-loss BSE imaging, revealing subcellular entities after contrast inversion. The resolution of low-loss BSE imaging was sufficient to resolve plasma membrane, and various types of vacuoles and vesicles. These results suggest that low-loss backscattered electron imaging could potentially provide compositional information to resolve surface chemical features of uncoated microbial cells and stained section-face with heterogeneous surface compositions.

UI MeSH Term Description Entries
D006999 Hypocreales An order of fungi in the phylum ASCOMYCOTA that includes a number of species which are parasitic on higher plants, insects, or fungi. Other species are saprotrophic. Hypocreale
D008855 Microscopy, Electron, Scanning Microscopy in which the object is examined directly by an electron beam scanning the specimen point-by-point. The image is constructed by detecting the products of specimen interactions that are projected above the plane of the sample, such as backscattered electrons. Although SCANNING TRANSMISSION ELECTRON MICROSCOPY also scans the specimen point by point with the electron beam, the image is constructed by detecting the electrons, or their interaction products that are transmitted through the sample plane, so that is a form of TRANSMISSION ELECTRON MICROSCOPY. Scanning Electron Microscopy,Electron Scanning Microscopy,Electron Microscopies, Scanning,Electron Microscopy, Scanning,Electron Scanning Microscopies,Microscopies, Electron Scanning,Microscopies, Scanning Electron,Microscopy, Electron Scanning,Microscopy, Scanning Electron,Scanning Electron Microscopies,Scanning Microscopies, Electron,Scanning Microscopy, Electron
D003287 Contrast Media Substances used to allow enhanced visualization of tissues. Radiopaque Media,Contrast Agent,Contrast Agents,Contrast Material,Contrast Materials,Radiocontrast Agent,Radiocontrast Agents,Radiocontrast Media,Agent, Contrast,Agent, Radiocontrast,Agents, Contrast,Agents, Radiocontrast,Material, Contrast,Materials, Contrast,Media, Contrast,Media, Radiocontrast,Media, Radiopaque
D013172 Spores, Fungal Reproductive bodies produced by fungi. Conidia,Fungal Spores,Conidium,Fungal Spore,Spore, Fungal
D013194 Staining and Labeling The marking of biological material with a dye or other reagent for the purpose of identifying and quantitating components of tissues, cells or their extracts. Histological Labeling,Staining,Histological Labelings,Labeling and Staining,Labeling, Histological,Labelings, Histological,Stainings
D025301 Hyphae Microscopic threadlike filaments in FUNGI that are filled with a layer of protoplasm. Collectively, the hyphae make up the MYCELIUM. Hypha,Hyphas

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