Microorganisms are extremely important to biology due to their fundamental basis on which life formed upon. However they are impossible to witness with the naked eye, therefore it is necessary to culture microorganisms to be able to see them underneath a microscope. As some microorganisms are pathogens culturing can be reasonably dangerous if not done properly. Aseptic technique is used to avoid any contamination of the culture or to avoid the risk of pathogenic organisms coming in contact with the person.
The first step is to wipe down any surfaces with ethanol, this kills any microorganisms within the vicinity of the culture.
Next a Bunsen burner is lit. The heat emitted causes the air around the flame to rise reducing the number of microorganisms around the area.
With the desired microorganisms in a broth, the top to the test tube is opened. The lip to the test tube is flamed sterilising it. The top is held in the same hand as the innoculating loop to prevent any contamination caused by placing it on the bench.
The innoculating loop is then sterilised by placing it in the hottest part of the roaring flame.
The innoculating loop is then place in the broth, while kept close to the bunsen burner.
The innoculating loop is then streaked across the medium being used, in this case agar. The lid of the petri dish is kept close to the agar to prevent any contaminants from the person or microorganisms from the air falling onto the agar. The agar usually contains nutrients allowing the microorganisms to function, with nitrates used for protein synthesis and DNA replication, this allows for the culture to grow. Other mediums can also be used, such as a nutrient broth. Selective mediums are also used to identify strains of microorganisms and possible antibiotic resistance. MacConkey agar for example grows Gram-negative bacteria.
The lid is placed on the petri dish and tape is used to seal the petri dish so that oxygen can still enter the culture allowing it to respire and grow.
The process is now completed, the culture is placed in a warm dry place for it to grow and after a few days colonies can be seen on the agar surface.
The process is now completed, the culture is placed in a warm dry place for it to grow and after a few days colonies can be seen on the agar surface.