Microscopy, Staining, and Classification

Practice flashcards covering microscopy principles, types of microscopes, staining techniques, microbial nomenclature, and prokaryotic morphology based on lecture slides.

Meter ($m$)

The standard metric unit of length, approximately equal to $39.37$ inches.

Micrometer ($\mu m$)

A metric unit of length equivalent to $1/1,000,000$ meter or $10^{-6}\,m$, typically used to measure white blood cells ($5-25\,\mu m$).

Nanometer ($nm$)

A metric unit of length equivalent to $1/1,000,000,000$ meter or $10^{-9}\,m$, typically used to measure viruses like poliovirus ($25\,nm$).

Resolution

The ability to distinguish two points that are close together; better resolution allows two nearby objects to be distinguished more clearly.

Contrast

Differences in intensity between two objects or between an object and its background, which is important for determining resolution.

Bright-Field Microscope

A type of compound light microscope that uses a series of lenses to pass light through a specimen; it often requires stained specimens for better visibility.

Total Magnification

Calculated by multiplying the magnification of the objective lens by the magnification of the ocular lens.

Oil Immersion Lens

A high-power lens (typically $100\times$) that uses immersion oil to increase resolution by preventing light rays from refracting away from the lens.

Phase-Contrast Microscope

A microscope commonly used to view living organisms and internal organs without staining, depending on light and dark areas for contrast.

Differential Interference Contrast (Nomarski) Microscope

A microscope that produces three-dimensional images by using differences in refractive index as light passes through the specimen.

Dark-Field Microscope

A microscope that highlights specimens against a dark background; it is useful for detecting organisms like Treponema pallidum, the causative agent of syphilis.

Fluorescence Microscopy

A technique that uses ultraviolet light to examine materials that emit light when struck by specific wavelengths.

Confocal Scanning Laser Microscope

Uses a laser to fluoresce only one plane of the specimen at a time to create detail sectional views or three-dimensional pictures of thick structures like biofilms.

Transmission Electron Microscope (TEM)

A microscope that transmits electrons through a specimen to observe fine internal details, with a resolving power of approximately $0.2\,nm$.

Scanning Electron Microscope (SEM)

A microscope that scans the surface of a specimen with electrons to produce three-dimensional surface images; it does not show internal structures.

Atomic Force Microscope

A type of probe microscope that measures the deflection of a laser beam aimed at a probe tip to observe living specimens at molecular and atomic levels.

Heat Fixation

The process of passing a slide through a flame to attach the specimen to the slide before staining.

Simple Stains

Stains composed of a single basic dye, such as crystal violet, safranin, or methylene blue, used to determine cell size, shape, and arrangement.

Differential Stains

Stains that use more than one dye to distinguish between different types of cells, chemicals, or structures; examples include the Gram stain and acid-fast stain.

Gram Stain

A four-step differential staining procedure involving a primary stain (crystal violet), a mordant (iodine), a decolorizer (acetone alcohol), and a counterstain (safranin).

Acid-Fast Stain

A differential stain used for organisms in the genera Mycobacterium and Nocardia, which have high mycolic acid content in their cell walls.

Endospore Stain

A special stain (such as the Schaeffer-Fulton stain) used to highlight the presence of endospores produced by species in the genera Bacillus and Clostridium.

Negative Stain

A staining technique that colors the background but leaves the specimen (such as a bacterial capsule) unstained or colored with a simple stain.

Binomial Nomenclature

A two-word naming system developed by Linnaeus consisting of a capitalized genus name and a lowercase species name, both of which are italicized or underlined.

Carl Woese

A scientist who proposed three domains (Eukarya, Bacteria, and Archaea) based on differences in ribosomal RNA (rRNA) nucleotide sequences.

Serological Tests

Tests that study antigen-antibody reactions to identify microorganisms that trigger an immune response.

Phage Typing

A method of identifying bacteria using bacteriophages, which are viruses that specifically infect certain host bacterial cells.

Dichotomous Key

A taxonomic tool consisting of a series of paired statements used to identify organisms based on presence or absence of specific characteristics.

Coccus

A spherical or berry-shaped prokaryotic cell.

Bacillus

A rod or cylinder-shaped prokaryotic cell.

Vibrio

A prokaryotic cell shape characterized as a curved rod.

Pleomorphic

A term used to describe bacteria that are able to vary their shape.

Streptococci

An arrangement of spherical bacteria that remain in chains after dividing in a single plane.

Sarcina

A cubical packet arrangement of eight cocci formed by division along three perpendicular planes.

Staphylococci

Grape-like clusters or sheets of cocci formed by division along several random planes.