17 Questions
What is the purpose of using sterile technique when inoculating an agar plate?
To ensure the growth of a single species of bacteria
Why is it important to cool the inoculating loop after heating it in the flame?
To handle the inoculum safely
What is the purpose of flaming the inoculating loop between each quadrant?
To sterilize the loop
Why are agar plates incubated upside down?
To reduce bacterial contamination and prevent water condensation
What is the purpose of labelling an agar plate?
To identify the agar plate
What is the primary goal of aseptic technique in a laboratory setting?
To prevent contamination of the environment with the organism in the culture
What happens to microbial suspensions after use?
They are placed in a biohazard bag and autoclaved
Why is it important to keep test tube caps and petri dish covers on media?
To reduce contamination of the media
What is the definition of sterilization?
The process of killing or removal of ALL microorganisms in a material or on an object
Why is it important to label test tubes and petri plates?
To keep track of the date, exercise number, and table number
What is the term for the absence of microbial contamination?
Asepsis
What is the purpose of flaming the wire loop after each streaking in the Streak Plate Method?
To sterilize the wire loop and prevent contamination
What is the primary goal of the Streak Plate Method?
To separate individual cells and obtain a pure culture
What is the term for a population of cells arising from a single cell?
Colony
What is the purpose of using a sterile wire loop in the Streak Plate Method?
To inoculate the agar plate with bacteria
What is the result of streaking the bacteria onto the agar plate in the Streak Plate Method?
Multiple colonies form, each derived from a single bacterial cell
What is the importance of storing agar plates in a labelled plastic bag at 4 °C?
To prevent contamination and preserve the plates for future use
Study Notes
Aseptic Technique and Sterilization
- Aseptic technique is used to prevent microbial contamination in laboratory experiments
- It involves preventing contamination of cultures with environmental microbes and preventing contamination of oneself or the environment with the organism in the culture
- Sterilization is the process of killing or removing all microorganisms, including spores, from a material or object
- There are no degrees of sterility; sterility means that there are no living organisms in or on a material
Preparation of Agar Plates
- Agar plates must be labelled with name, name of organism, date, table number, exercise number, and other relevant details
- Plates must be incubated upside down to reduce bacterial contamination and prevent water condensation from dropping onto the agar
- Plates can be stored in labelled plastic bags at 4°C (refrigerator) for future use
Streak Plate Method
- The streak plate method is used to obtain pure cultures of bacteria
- A wire loop is used to pick up a small amount of bacteria and streak it onto the agar surface in four quadrants
- The wire loop is flamed between each quadrant to prevent contamination
- The goal is to separate individual bacterial cells and obtain isolated colonies in the later quadrants
- Colonies are masses of offspring from an individual cell, also known as colony-forming units (CFU)
General Laboratory Practices
- Inoculation loops must be heated in a flame and cooled before use to prevent contamination
- Samples must not be dumped down the drain or in the trash can; they must be placed in biohazard bags and autoclaved
- Test tubes and petri dishes must be labelled and kept upright to prevent leakage and contamination
- Laboratory surfaces must be cleaned and disinfected regularly to prevent microbial growth
Learn about microbiology lab techniques such as the streak plate method, pour plate method, and spread plate method for obtaining pure cultures of bacteria.
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