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An Investigation to measure the effect of different antiseptics on bacterial cells.

Background Knowledge

Bacteria are unicellular organisms that are only visible under the use of a high power light microscope. They are different to plant and animal cells because they have a single chromosome in the form of a single strand of DNA and it is not contained within a nucleus, Bacterial cells have a cell wall that is sometimes surrounded by a slime capsule.




Some bacteria have filaments (flagella), which flick and allow the bacteria to move.
Bacteria can cause diseases, such as salmonella (food poisoning), gonorrhoea (a sexually transmitted disease) and diphtheria.

Antiseptics are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection or sepsis. Some antiseptics are true germicides, capable of destroying microbes, whilst others are bacteriostatic and only prevent or inhibit their growth. The first antiseptic used was phenol, by Joseph Lister, who would spray the phenol in the air around a wound, and then soak the bandages used to dress the wound in phenol.
In modern operating theatres antiseptic sprays are no longer used. Instead, aseptic techniques are used. This means trying to create an environment that is free from harmful microbes. This is achieved in operating theatres by having the air filtered, using sterile instruments, and the use of facemasks and gloves by surgeons.

We will be working with a type of bacteria found on the skin.

The aim of this investigation is to find out what concentration of antiseptic is the most effective against these bacteria.

Bacteria can be grown on nutrient agar jelly. The agar provides a supply of water and food. Other conditions for growth are a warm temperature and enough oxygen for respiration.

I will create four small wells in...