Culturing Microorganisms Part 1 | Cells | Biology | FuseSchool

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Culturing Microorganisms Part 1 | Cells | Biology | FuseSchool

Bacteria are a type of microorganism. If they have enough nutrients and are in a suitable temperature, bacteria can multiply once every 20 minutes. So, after one hour a single bacterium could have reproduced to give eight bacteria.

They undergo simple cell division known as binary fission.

Bacteria, and other microorganisms can be grown in a lab. They can be grown in a nutrient broth solution or as colonies on an agar gel plate, but need certain conditions to flourish.

We use cultures of microorganisms to investigate the action of disinfectants and antibiotics. But to do this, the cultures cannot be contaminated. This means that precautions must be taken to stop unwanted microorganisms growing as well.

In this video, we are going to discover how to culture microorganisms on agar jelly in a petri dish. In part 2 we will look at how to do calculations with our colonies, from predicting colony sizes and also calculating areas.

Microorganisms are grown, or cultured, in a growth medium… which is the agar jelly.

To grow, they need carbohydrates for energy, and mineral ions. They may also need extra proteins and vitamins. This is all found in the agar jelly.

When hot, the agar jelly is poured into petri dishes - these shallow round plastic dishes - where it then sets.

Once the agar jelly has cooled and set, an inoculating loop is used to transfer the microorganism onto the agar jelly.

To ensure unwanted microorganisms from the air don’t also grow, the petri dish, agar jelly and inoculating loop must be sterilised first.

We can sterilise our inoculating loop by passing it across a hot flame before use.

The petri dish must have a lid on it always to ensure unwanted contamination doesn’t occur. The lid should be taped on to prevent any accidental removal and stored upside down.

Bacteria grow and reproduce more quickly when they are warm. In labs in schools, the microorganisms are usually kept at about 25 degrees celsius as this is a safe temperature. Although 37 degrees celsius would be better, in schools this is dangerous as it might allow the growth of harmful pathogens which are bad for our health.

In industrial conditions, the cultures can be kept at higher temperatures to allow faster growth and division as better precautions can be taken to control any growth of harmful pathogens.

From this video, we discovered how to culture microorganisms on agar jelly in a petri dish, preventing any contamination.

In part 2 we will look at how to do calculations with our colonies, from predicting colony sizes and also calculating areas.



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