Binary Fission Flashcards
What type of cells use binary fission?
Prokaryotic cells e.g. bacteria
What is binary fission?
A means of asexual reproduction or cell division
What are
What are plasmids?
They are circles of DNA which contain non essential genes.
What are the aims of the practical for culturing microorganisms practical?
.to investigate the effects of antiseptics or antibiotics on bacterial growth
What is a culture medium?
It contains the carbohydrates, minerals, proteins and vitamins the bacteria need to grow.
What two culture mediums can be used?
Agar jelly and nutrient broth solutuion
How do you uses nutrient broth solution to culture microorganisms?
It involves making a suspension of bacteria to be grown and mixing with sterile nutrient broth stoppering the flask with cotton wool to prevent air from contaminating it and shaking regularly to provide oxygen for the growing bacteria.
What happens when we use agar jelly?
The bacteria will form visible colonies on the surface of the jelly or spread out to give an even covering of bacteria.
Aseptic techniques
- Wash hands and clean surfaces
- Sterilise petri dishes and culture mediums
- Sterilise inoculating loop
- Seal the lid of the petri dish
- Incubate petri dish upside down
- Incubate at 25ºC
Why should you wash your hands and clean the work surfaces before beginning?
To prevent contamination
How do you sterilise the petri dishes and culture mediums?
by heating to a high temperature) often done by an autoclave (oven) or UV light. If it’s a glass petri dish you need to sterilise it or you can just buy pre-sterilised plastic ones.
Why should you sterilise the petri dishes and culture mediums before use?
If this step doesn’t take place they can be contaminated with other microorganisms. These could be harmless and compete with the desired bacteria for space. They can also be harmful and potentially produce a new pathogen.
How do you sterilise the inoculating loop?
By passing it through a hot flame.
Why do we need to sterilise the inoculating loop?
Kills unwanted microorganisms.If this step doesn’t take place they can be contaminated with other microorganisms. These could be harmless and compete with the desired bacteria for space. They can also be harmful and potentially produce a new pathogen
How do you seal the lid of the petri dish?
Seal it with tape but not completely
Why do we need to seal the petri dish in this way?
This stops airborne microorganisms from contaminating the culture. But it shouldn’t be sealed all the way to prevent harmful anaerobic bacteria from growing due to the lack of oxygen.
Why should the petri dish be stored/incubated upside down?
This is to prevent condensation from the lid landing on the agar surface and disrupting growth
When do we usually incubate the culture at 25ºC?
in school labs
Why do we incubate the culture at 25ºC?
This is because, if it were incubated at a higher temperature closer to 37ºC (human body temp) it’s be more likely that bacteria that could be harmful to humans could grow as this is their optimum temperature. At lower temperatures (25ºC), colonies of such harmful bacteria wouldn’t be able to grow.
When are cultures incubated at higher temperatures?
In industrial conditions
