Bacteria multiply by a type of simple cell division in which the bacterial cells split in two. This process is known as binary fission.
1. Under optimal conditions (the availability of nutrients and suitable temperature), the bacterial cell prepares for division.
2. The bacterial cell replicates the genetic material inside it and increases in size.
3. Each circular piece of DNA moves to opposite ends.
4. The cytoplasm divides
5. The bacterium cell becomes two daughter cells.
Some species of bacteria, such as E. coli, can replicate in as little as 20 minutes. So, the number of bacteria can increase very rapidly. Two ways bacteria can be cultured are:
They both contain all the essential nutrients that bacteria need to live and grow successfully.
Under optimal conditions, a bacterial cell divides every 20 minutes. Calculate the number of bacteria present after 8 hours.
It is important to sterilise solutions and equipment to kill the bacteria already present. Otherwise, they will grow and contaminate the culture that you are analysing.
An uncontaminated culture of microorganisms can be grown using sterilised petri dishes and agar jelly. First, we sterilise the inoculating loop before use and secure the lid of the Petri dish to prevent unwanted microorganisms from entering. After this, we pour hot agar jelly into a sterilised petri-dish and leave it to set and cool.
Uncontaminated cultures of microorganisms are used to investigate the effects of disinfectants and antibiotics. Bacterial cultures should be incubated at a maximum temperature of 25°C in schools and colleges to reduce the likelihood of pathogens growing that might be harmful to humans.
Aseptic techniques are used to prevent contamination by specific microorganisms, such as bacteria and fungi, in a lab. These techniques are also used to prevent contamination of the room and the people working with the microorganisms.
Let’s look at a few aseptic techniques that are important when growing uncontaminated cultures of bacteria.
Avoiding incubating bacterial cultures at human body temperature (or above 30°C) reduces the risk of growing pathogens that are harmful to humans.