tools of the laboratory

Inoculation

Introduces a tiny sample into a container of nutrient medium.

Incubation

Placed in a temperature controlled chamber to encourage growth.

Isolation

Once the cultures have grown, they may need to be re-inoculated in such way that separate species are obtained.

Inspection

The colonies on the agar or broth cultures are observed macroscopically and microscopically, possibly with the aid of staining.

Identification

the identity of the isolated microbe is determined, usually to the species level.

General purpose media

Designed to grow as many different types of microbes as possible

Enriched medium

Contains complex organic substances such as blood, serum, and hemoglobin, or special growth factors.

Fastidious

Bacteria that require growth factors and complex nutrients.

Selective medium

Contains one or more agents that inhibit the growth of a certain microbe or microbes.

Differential media

Allow multiple types of microorganisms to grow but are designed to display visible difference among their colonies.

Hemolysins

Enzyme that function to lose red blood cells for the purpose of releasing iron-rich hemoglobin for growth.

Reducing medium

Contains a substance that absorbs oxygen or slows the penetration of oxygen in the medium, which reduces it availability.

Carbohydrate fermentation media

Contains sugars that can be fermented and a pH indicator to show this reaction.

Transport media

Used to maintain and preserve specimens that have to be held for a period of time before clinical analysis to sustain delicate species that die rapidly if not held under stable conditions

Assay media

Used by technologists to test the effectiveness of antimicrobial drugs and drug manufacturers to assess the effect.

Pure culture

A container of medium growing only a single known species or type of microorganism.

Mixed culture

Is a container that holds two or more identified, easily differentiated species of microorganisms.

Contaminated culture

Once pure or even intentionally mixed but has since had contaminants introduced into it.

Refraction

The bending or change in the angle of the light ray as it passes through a medium such as lens.

Real image

Objective forms the initial image of the specimen.

Virtual image

The ocular lens forms a second image

Resolving power

The minimum distance two objects can be apart and still be distinguished separately.

Refractive index

Refers to the degree of bending that light undergoes as it passes from one medium to another medium.

Positive stain

The dye actually sticks to the specimen and gives it color.

Negative stain

The dye does not stick to the specimen but settles around its outer boundary.

Simple stains

Requires only a single dye

Differential stains

Uses two colors of dye

Gram-positive

Gram stain is PURPLE

Gram-negative

Gram stain is PINK - RED