Microscopy and Laboratory Culture of Microorganisms

A set of vocabulary flashcards defining key microscopy techniques, electron microscopy, staining procedures, and laboratory culture media concepts.

Resolution

The ability to distinguish two adjacent objects as distinct and separate.

Total Magnification

The overall magnification of a compound light microscope, calculated by multiplying objective magnification by ocular magnification, with an upper limit of about $2000\times$.

Immersion Oil

A substance used in light microscopy to increase the amount of light that enters the lens, thereby improving resolution.

Bright-Field Microscopy

A form of light microscopy where specimens are visualized due to slight differences in contrast between them and their surroundings.

Basic Dyes

Positively charged stains, such as methylene blue, crystal violet, and safranin, that bind to negatively charged cell components including nucleic acids, proteins, and cell surfaces.

Differential Stains

Staining procedures, such as the Gram stain, that stain different kinds of cells different colors.

Gram Stain

A differential stain that divides Bacteria into two major groups based on cell wall structure: gram-positive (purple) and gram-negative (pink).

Acid-Fast Stain

A differential stain used to identify acid-fast organisms (such as genus Mycobacterium) whose cell wall surface is attached to mycolic acid, producing a wax-like hydrophobic coating.

Phase-Contrast Microscopy

A form of light microscopy that uses a phase ring to amplify subtle differences in how materials slow light, visualizing darker cells on a light background.

Dark-Field Microscopy

A form of light microscopy in which the central portion of the light beam is blocked so light reaches the specimen from the sides only, visualizing light cells on a dark background.

Fluorescence Microscopy

Microscopy used to visualize specimens that emit light of one color after absorbing light of another color, relying on natural fluorescence or fluorescent dyes like DAPI.

Differential Interference Contrast (DIC) Microscopy

Microscopy that uses a polarizer and prism to generate two distinct light beams, enhancing subtle structural differences to give cells a 3-dimensional appearance.

Confocal Scanning Laser Microscopy (CSLM)

A computerized microscope coupled with a laser source that compiles images from individual focus planes to construct 3-dimensional views with resolution improved to $0.1\,\mu\text{m}$.

Transmission Electron Microscopy (TEM)

Microscopy that passes an electron beam through ultrathin tissue sections ($20 - 60\,\text{nm}$) stained with heavy metals to achieve an image resolution of $0.2\,\text{nm}$.

Scanning Electron Microscopy (SEM)

Microscopy in which an electron beam scans back and forth across a heavy-metal-coated specimen to produce black and white surface images.

Macronutrients

Chemical compounds and elements required by cells in large amounts to support growth and metabolism.

Micronutrients

Trace chemical elements required by cells in small amounts, typically less than $0.01\%$ of total mass.

Defined Media

Culture media prepared with precise amounts of pure chemicals in distilled water, where the exact chemical composition is known.

Complex Media

Culture media made from digests of microbial, animal, or plant products (such as casein, beef extract, or yeast extract) whose precise nutritional composition is not known.

Selective Media

Culture media containing specific compounds that inhibit the growth of some microorganisms while allowing others to grow.

Differential Media

Culture media containing indicators or additives that allow microorganisms to be distinguished based on the appearance of the colony or surrounding media.

Enriched Media

Complex culture media supplemented with extra nutritious additives like serum or blood (e.g., blood agar or chocolate agar) for growing nutritionally demanding microbes.

Aseptic Transfer Technique

Laboratory handling methods used to prevent contamination of sterile objects, media, or microbial cultures.

Streak Plate

A method used to produce isolated colonies and obtain pure cultures by drawing sequential streaks of inoculum across an agar plate using a sterile loop.