Isolation Methods

What kind of culture contains more than one type of organism?

Mixed culture

What method is used here

Quadrant streak plate method

What kind of culture contains only one species of organism, with all members genetically identical?

Pure culture

What type of methods do you need to get a pure culture?

Isolation methods (e.g., streak plate or pour plate)

What does CFU stand for?

Colony‑forming unit

What kind of plate establishes a concentration gradient of bacteria across the agar surface to separate the cells and get isolated colonies?

Streak plate

What is the method used to make a streak plate called?

The streak‑for‑isolation method (also called quadrant streaking)

Do you obtain additional samples from the culture for quadrants 2, 3, and 4 when making a streak plate?

No. You only dip into the culture once; the rest is dilution by streaking

What type of method involves a bacterial culture being diluted into a series of liquified agar tubes, and then poured into plates for solidification?

Pour plate method

What is the term for cooling the agar tubes so they won’t kill the bacteria, but remain liquid?

Tempering

What happens if you don’t pour the agar tubes quickly?

They will solidify in the tube (and you can’t pour them).

What two types of colonies can you get when making pour plates?

Surface colonies, Subsurface (embedded) colonies

Would strict aerobes make subsurface colonies?

No. Strict aerobes only grow where oxygen is available — the surface.

Which isolation method requires less skill, but more time and materials?

Pour plate method

Which isolation method allows for quantification?

Pour plate method (because you can count CFUs from known dilutions)