Fundamental Skills for Microbiology Lab Flashcards
What is a microbial culture?
A medium that contains living microbes
What is a pure culture?
A culture that contains a single species
What does the term ‘aseptic’ or ‘aseptically’ mean?
Transfer microbes from their pure culture to a sterile medium without disease / contamination
What does it mean to ‘culture’ a microorganism?
A sample (inoculum) is introduced to a collection of nutrients (medium)
What is an inoculum?
The source material / sample used for inoculation
What is a medium in the context of culturing microorganisms?
A liquid / gel designed to support the growth of microorganisms
What is a microbial colony?
A culture that is visible on the surface of solid media
What must be done to inoculating instruments to prevent contamination?
Instruments are sterilized immediately before use in a bunsen burner flame
Differentiate between inoculating loops and inoculating needles
- Inoculating loops are used to retrieve liquid media
- Inoculating needles are used to retrieve solid / dense media
What special precautions should be taken with tubes or flasks (specifically the ‘necks’ of these items) to insure aseptic technique is successful?
The mouths / tubes or flasks containing cultures are also incinerated at the time of transfer by passing their opening through a flame
Differentiate between transfer pipettes and pasteur pipettes
- Transfer pipettes have a rubber bulb
- Pasteur pipettes have a glass bulb
How must a tube culture, or any tubed-samples, be held?
By the tube - not the cap
How should the inoculating instrument be held?
Like a pencil - in the dominant hand
How should the Bunsen burner be adjusted for proper use?
Adjust the bunsen burner so the flame has an inner and outer cone
What is a mixed culture?
A microbial culture consisting of 2 or more species
What is the most commonly used isolation technique in microbiology?
The streak plate method
What is the goal of any streak plate isolation method?
To obtain isolated colonies from an inoculum by creating areas of increasing dilution on a single plate
Is the quadrant streak plate method most applicable to cultures having a high or low initial cell density?
High cell density
What tool is used in the streak plate method?
An inoculating loop
Differentiate between ‘colonies’ and ‘colony-forming units’ (CFUs)
- Colonies are groups of bacteria that grew from an original bacterium
- Colony-forming units measure viable cells
Describe serial dilution (2)
- A series of dilutions in which the dilution factor remains the same for each step
- Allows estimation of a sample’s concentration
Describe how the spread plate method of isolation is performed
A method of isolation in which diluted microbial sample is deposited on an agar plate and spread uniformly across the surface
What tool is used in the spread plate method?
A glass rod
