How to Culture Microorganisms in the Lab

Pour plate

Used to identify the number of colony forming units in a solution - may involve a serial dilution

Lawn plate

Use a spreader to spread out the bacterial colonies

These can be used to identify colonies that have been genetically engineered

Streak plate

Used to separate colonies of bacteria

Why do we use aseptic conditions?

To avoid any unwanted microbes that would:

- compete for nutrients

- change the conditions in a fermenter

- decrease the yield of product

- contaminate the batch

Plates should not be incubated at 35 degrees

Could lead to the growth of human pathogens

Flaming the neck of tube

Causes air to expand and push bacteria away, so less likely to settle in the tube.

Also kills bacteria on the neck of the tube

The lid should be held above the dish when adding solutions

Avoids contamination with bacteria from the air

When incubating the plate, they should be kept upside down

Prevents condensation droplets from forming on the lid and dripping onto the agar surface, which can contaminate the culture and interfere with colony growth