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Chapter 4: Microscopy, Staining, and Classification Units of Measurement The meter is the standard unit of measurement for length. All other measurements are fractions of a meter with bases of 10: Decimeter- 1/10 of a meter Centimeter- 1/100 of a meter Millimeter- 1/1 000 of a meter Micrometer (micron)- 1/ 1 000 000 of a meter Nanometer- 1/ 1 000 000 000 of a meter Microscopy General Principles of Microscopy -wavelength of radiation-magnification-resolution-contrastLight Microscopy- uses various types of light to examine microscopic specimens -Bright-field microscope-Dark-field microscope-Phase microscopes-Fluorescent microscopes-Confocal MicroscopesElectron Microscopy- uses electrons to increase the resolution of specimens. -TEM-SEM- 1 Probe Microscopy- uses pointed electronic probes -Scanning Tunneling Microscope-Atomic Force MicroscopeStaining Preparing Specimens for Staining Principles of Staining -dyes used for staining are either acidic (negatively charged) or basic (positively charged) -staining occurs due to the bonding of the dyes to various parts of the cell -some stains do not create chemical bonds, but accumulate in certain parts of the cell. Simple Stains- Differential Stains- -Gram Stain is the most frequently used stain in microbiology, the four steps in the process: 1. 2. 3. 4. 2 -Acid-Fast Stain is used to identify the genera Mycobacterium and Nocardia, causes many human diseases -cells have large amounts of waxy lipid, do not readily stain with simple water-based dye. The steps for acid-fast staining: 1. 2. 3. 4. -Endospore Stain is used to identify bacteria that form endospores -Histological Stains are used mainly for tissue samples Special Stains- simple stains designed to reveal special microbial structures -Negative and Capsule Stain-Flagellar Stain- Classification and Identification of Microorganisms TaxonomyTaxaLinnaeus and Taxonomic Categories -Linnaeus created the current system of taxonomy in 1758 -divides organisms into increasingly detailed groups: 3 -uses binomial nomenclature to create a scientific name, uses the genus and species names. -scientific names are usually descriptive. Domains- Proposed in 1976, three different domains: Eukarya Bacteria Archaea Taxonomic and Identifying Characteristics -Bergey’s Manual- Two manuals that are used for identification of prokaryotes. -Physical Characteristics-Biochemical Tests-Serological Tests-Phage Typing-Analysis of Nucleic Acids-Taxonomic Keys- 4