Introduction to Microbiology Culturing and Microscopy

Vocabulary practice cards covering the five I's of culturing, media types, microscopy varieties, and staining techniques for microbiology.

Culture

The growth that appears in or on growth media after inoculation or when microorganisms are introduced to the media.

Mixed culture

A culture that contains more than one species of microorganism.

Pure culture

A culture that contains a single species of microorganism; also referred to as axenic.

Axenic

A term used interchangeably with pure culture to describe a growth containing only one species.

Subculture

A method used to obtain a pure culture by sampling a single colony from a mixed culture plate and growing it on a new plate.

Contaminants

Microorganisms that are unintentionally introduced to a culture, usually caused by poor aseptic technique.

The Five I's

The basic techniques used in the laboratory for culturing microorganisms: inoculation, incubation, isolation, inspection, and identification.

Inoculation

The process of introducing a small sample into a growth medium.

Inoculum

The small sample of microorganisms used for inoculation.

Incubation

The step where a culture is kept at an appropriate temperature, usually for "twenty four" to "forty eight" hours, to allow for growth.

Isolation

The process of separating individual species from a mixed culture using techniques like the streak plate, pour plate, or spread plate.

Inspection

Observing a culture both microscopically (with a microscope) and macroscopically (with the naked eye) after incubation.

Identification

The final step of culturing using additional tests such as biochemical, immunologic, and genetic analysis to determine the organism type.

Broth

A common name for growth media in a liquid physical state.

Semi-solid media

Media containing a small amount of agar that acts as a solidifying agent, resulting in a thick liquid or soft gel consistency.

Agar

A solidifying agent used to give growth media a firm consistency similar to gelatin or jello.

Solid media

Media that holds its shape even at warm incubation temperatures, often referred to as agars.

Defined media

Also called synthetic media, this classification has all chemical components known and quantified by a precise recipe.

Complex media

Media containing at least one unknown component, such as blood agar, where the exact composition may vary.

General purpose media

Media designed to support the growth of many different types of organisms.

Enriched media

Media containing special organic substances or growth factors, like vitamins or amino acids, required by fastidious organisms.

Fastidious

A term describing microorganisms that are "picky eaters" and require specific nutrients in enriched media to grow.

Selective media

Media containing substances that inhibit the growth of certain organisms while allowing others to grow.

Mannitol salt agar (MSA)

A selective medium with high salt concentration that inhibits many organisms but allows the isolation of Staphylococcus species.

Differential media

Media that allows multiple types of organisms to grow but differentiates them based on colony appearance or changes in the surrounding agar.

Bright field microscope

A microscope where light is transmitted through the specimen, usually requiring the application of dye to create contrast.

Dark field microscope

A microscope that uses a dark background with illuminated cells, allowing for the observation of living specimens without dye.

Phase contrast microscopy

A technique where different densities of the specimen appear as different colors, revealing internal structures without staining.

Differential interference microscopy

A microscopy type that visualizes internal structures without stain, producing images that appear more three-dimensional than phase contrast.

Fluorescent microscope

A microscope used diagnostically that utilizes antibodies with an attached fluorochrome to identify specific pathogens like the rabies virus.

Fluorochrome

A fluorescent pigment attached to an antibody used in fluorescent microscopy.

Transmission electron microscopy (TEM)

An electron microscopy method that shows a thin cross-section of a specimen to reveal internal structures.

Scanning electron microscope (SEM)

An electron microscopy method that creates a detailed surface image of the specimen.

Smear

A liquid suspension of cells spread into a thin film on a slide and allowed to air dry.

Fixation

A process using heat or chemicals to stick cells to a microscope slide and kill them.

Simple stain

A staining technique that uses a single dye to determine the relative size, shape, and arrangement of cells.

Differential stain

A staining technique using two or more dyes to distinguish between different types of cells or internal cell structures.

Gram stain

A differential stain using a two-dye technique to determine the structure of bacterial cell walls, identifying gram positive or gram negative cells.

Endospore stain

A differential stain that distinguishes between the vegetative cell (red) and the internal endospore (green).

Vegetative cell

The active, living cell identified in an endospore stain, which stains red.