Culturing Microorganisms Flashcards
What is the point of growing microorganisms?
To test how effective different antibiotics, antiseptics, or disinfectants are at killing them.
What does it mean to culture bacteria?
It means t.o grow bacterial cells in a controlled environment, typically using a nutrient rich medium that contains the carbohydrates, minerals, proteins, and vitamins needed for them to grow.
What are the 2 culture mediums that can be used?
A nutrient broth solution or a solid agar jelly
What will bacteria grown on agar plates form?
Visible colonies on the surface of the jelly
How do you make an agar plate?
To make an agar plate, hot agar welly is poured into shallow round plastic dishes called Petri dishes.
When the jelly is cool and set, inoculating loops can be used to transfer microorganisms to the culture
medium.
Alternatively, a sterile dropping pipette and spreader can be used to get an even covering of bacteria.
The microorganisms then multiply.
What temperature are cultures of microorganisms supposed to be kept at?
25°C
Why are you supposed to keep cultured microorganisms at 25°C in a school practical?
Because harmful pathogens are more likely to grow above 25°C.
Un industrial conditions, how can you get cultures to grow faster?
Incubate them at a higher temperature.
Why do you need to use uncontaminated cultures?
So contamination by unwanted microorganisms won’t affect your results.it can also potentially result in the growth of pathogens.
How can you avoid contamination?
The petri dishes and culture medium must be sterilised before use to kill any unwanted microorganisms on them.
If an inoculating loop is used to transfer the bacteria to the culture medium, A should be sterilised first by passing it through aflame.
After transferring the bacteria, the lid of the petri dish should be lightly taped on. This is to stop microorganisms from the air getting in.
The petre dish should be stored upside down to prevent drops of condensation falling onto the agar surface.
What are the steps of testing the action of antibiotics on bacterial growth?
Start off by placing paper discs soaked In different types / concentrations of antibiotics on an agar plate that has an even covering of bacteria. Make sure to leave space between the disks.
The antibiotic should diffuse (soak) into the agar jelly. Antibiotic resistant bacteria will continue to grow on the agar around the paper discs, but non-resistant bacteria will die. A clear area will be left.
Make sure to use a control. This is a paper disc that has not been soaked in an antibiotic. Instead, soak it in sterile water.Then you can be sure that any difference between the growth of the bacteria around the control disc and around one of the antibiotic discs is due to the affect of the antibiotic alone and not something wrong with the paper.
Then leave the plate for 48 hours at 25°C.
What do you call the clear area that shows that bacteria was killed?
Inhibitition zone
How do you know which antibiotic is the most effective?
The more effective the antibiotic is against bacteria, the larger the intibitition zone will be.
How can you calculate the area of an inhibition zone?
Measuring their diameter
What is the equation for calculating area?
Area=πr²
How do you calculate the area if you are given the diameter, not the radius?
Divide the diameter by 2
How do you measure the diameter if the inhibition zone isn’t a perfect circle?
Measure the diameter in more than one direction, and then work out a mean
