2, 6, 7, 8 Lab Exercise

Aseptic technique

Practices done to prevent contamination of culture and possibility of the culture contaminating you and others

» washing hands before and after lab

» disinfecting desktop before and after lab

» work close to bunsen burner → keep environment sterile

» keep cultures and media covered

» wear gloves

Culture

Growth of bacteria in/on culture media

Culture medium

What bacteria grow on. Can be liquid or solid (has agar applied to it)

» liquid → broth

» solid→ agar plate: has high SA. enables you to count visible formations of colonies and their morphology

→ agar slant: high SA. enables you to observe growth on surface

→ agar deep: low SA. enables you to observe bacteria’s movement accoding to its oxygen requirements

Agar

Compound added to culture medium to turn it solid. Used over gelatin as it cannot be consumed by bacteria

Bacterial colony

Visible mass of cells arising from a single cluster of cells

Can be used to grow a

» pure culture: culture that contains only one type of organism (clones that arose from a single, separated [__]!)

» mixed culture: culture that contains colonies of multiple species

Streak-plate method

Method to isolate colonies by streaking a medium, sterilizing our loop, and pulling from previously streaked area into 4 quadrants

» streaking dilutes bacterium across a solid agar and thereby isolates them!

Pure culture

The importance of obtaining a [__], often done by isolating for a single colony by the streak-plate method, is to:

» study properties of individual species without interference from other species

» determine how many types of bacteria are present in a medium

» identify those likely to be causing the patient’s disease

» test which antimicrobial agents will be effective for treatment

Subculture

To [__] (verb), you transfer a single colony to a fresh new agar plate

» each colony grown in this [__] will be a clone as they were derived from that single cell → how pure cultures are made

[__](n.): new pure culture of isolated organisms

» you can tell it’s a pure culture by if it has the same colonial morphology, biochemical and immunological properties

nutrient

Media are chosen based on if they provide nutrients essential for growth of the microorganism studied

• All media require 3 components to support microorganisms:

» protein materials (peptides, proteoses, peptones, amino acids)

→ often provided as meat extracts and partially cooked meats

» carbon source (carbohydrates)

» mineral salts (osmotic/pH buffer)

• can be further enriched into various forms of media, such as a blood agar

• A [__] broth or [__] agar plate the most basic form of media you can have → basal broth prepared from meat extract and lacking special enrichment

autoclaving

Creating a culture media first takes form in a dehydrated powder that gets added to distilled water

It then undergoes:

» boiling to dissolve the powder

» [__] to sterilize the agar media mixture

» aseptic addition of agar to solidify the mixture

inverted

Agar plates are stored [__] or incubated agar-side up because

» prevents condensing moisture to accumulate on agar surface

» prevent bacterial colony merging and smearing by such condensation

Colonial morphology

[__]: Observation of the noticeable, gross features of colonies

1. color

2. density (translucent, opaque?)

3. consistency (creamy, dry, flaky?)

4. form: top view of shape

5. elevation: side view of shape

in addition to their oxygen tolerance (in liquid medium, telling of their anaerobic tendencies) can help identify species

Circular

Type of form you can see colonies as

Irregular

Type of form you can see colonies as

Filamentous

Type of form you can see colonies as

Punctiform

Type of form you can see colonies as

Means “pinpoint”

Flat

Type of elevation you can see colonies as

Raised

Type of elevation you can see colonies as

Convex

Type of elevation you can see colonies as

Umbilicate

Type of elevation you can see colonies as. Collapsed in the center.

Umbonate

Type of elevation you can see colonies as. Heaped