Bacteria and Disinfectants
Purpose:
How concentration can affect the performance rate of disinfectant in killing micro-organisms.
Hypothesis:
I predict that when the concentration of Savlon is increased that the clear zone size will also increase.
Hypothesis:
I predict that when the concentration of Savlon is increased that the clear zone size will also increase.
Equipment:
- 3 Agar Plates
- Savlon
- Tweezers
- Filter Paper
- Ethanol
- Bunsen Burner
- Yoghurt (for the bacteria)
- Permanent Marker
- Sellotape
- Pipette
- Water
- Spotting Tile
Concentrations:
One control 0% - Water
Savlon
One 100%
One 50%
One 10%
Variables:
- Independent Variable: The concentration of the disinfectant, in this case Savlon
- Dependant Variable: The clear zone. Or the area where the bacteria was not able to grow. We will measure the diameter in mm
- Control Variables: 1) Size of filter paper, used a hole punch of the same size, (2) type of disinfectant, only used savlon and no other type of disinfectant (3) size of agar plate used three of the exact same agar of the exact same size.
Possible factors for a source of error
- Contamination of Agar plate
- Cracking the agar
- Not sterilising tweezers
- amount of yoghurt differing agar to agar
Method:
- With a permanent marker, mark out four sections on the bottom of the plate on the side where the gel is located. These four sections will hold the different concentrations of Savlon and the Control.
- Spread some yoghurt acting as bacteria on top of the gel inside the agar plate.
- once the yoghurt has covered the agar we will drain the excess.
- we will then dilute the Savlon into three concentrations of 100% 50% and 10% using the pipette and Spotting Tile place 10 drops of Savlon in 1 spot of the tile, 5 drops of savlon and 5 drops of water in another spot, then 1 drop of savlon and 9 drops of water in another spot and then 10 spots of water in another one. you should have 4 spots in the tile filled with these solutions.
- using filter paper and a hole punch cut out 12 circles, 4 for each plate
- using these circles and sterilising the tweezers by dipping in ethanol and running through the Bunsen burner after each time, dip the circles into the different concentrations and water then place in the different sections.
- after this we will tape it up, put our initials on it and place it in incubation.
- Then measure the diameter of the clear zone in millimetres.
Outcome:
Conclusion:
After analysing the results of our experiment and placing them in a table and a line graph we have concluded that when the concentration of Savlon is increased the size of the clear zone also increases. The savlon worked by not killing the bacteria but actually preventing it to grow and as we increased the Savlon it worked better and prevented more bacteria from growing.
Discussion:
The active ingredient in Savlon is chlorhexidine. Chlorhexidine is used as a disinfectant and an antiseptic. Savlon is bacteriostatic meaning that it prevents the growth and reproduction of bacteria. bacteriostatic disinfectants work by interupting the growth and reproduction cycle. They do this by interfering with the protein growth within the cell and also the DNA replication. By doing this the cell is not able to create offspring because they are unable to pass on their DNA.
Bacteria is made up of a capsule, cell wall, cell membrane, chromosome, plasmids, ribosomes, pili and a flagellum. The capsule helps keep the cell safe, the cell wall holds the structure of the cell, the cell membrane controls the nutrition and excretion of the cell, the chromosome hold the DNA of the cell, the plasmids hold extra DNA, the ribosomes are where protein is produced, the pili is used for transferring DNA between cells and the flagellum is used to move the cell. Since the cell membrane is what controls what comes in and out this means that the disinfectant breaks through the Cell wall, enters through the cell membrane and destroys the Chromosome which holds the DNA making the Bacteria cell unable to reproduce. Bacteria cells excrete and gain nutrition through their cell membranes. They do this by using active or passive transport.
Bacteria grow by replicating the DNA of the parent cell, after this they grow/elongate, after this stage they then split into two seperate cells and the reproduction cycle is complete. Bacteria reproduce very rapidly as they split into two from every parent cell. This means that the Bacteria is asexual. Since the Bacteria is self producing, when one Bacteria's DNA is destroyed there is no way for any more Bacteria to be reproduced from that certain cell. When the disinfectant is spread through a whole colony all of those Bacteria are rendered unable to reproduce. Passive transport is when there is a high concentration of molecules outside of the cell and a low concentration inside and the cell naturally diffuses the high concentration inside of the cell. Active transport is when there is a low concentration outside of the cell and a high concentration inside and the cell has to use energy to transport the molecules. So when a disinfectant is introduced to a bacteria cell it will enter the passive transport cycle and naturally diffuse into cell causing the chromosome to be destroyed.
Evaluation:
The Method we used was very effective, they were easy to follow and nothing went wrong. The method was reliable as the size of the clear zone varied because of the different concentration which is what we wanted. The size of the clear zones from each concentration on the different agars differed slightly but they remained relatively close. The averages are probably a little close together which could come down to not enough time letting the bacteria grow or putting to much Savlon on the filter paper resulting in the results not being extremely varied.
Research:
https://en.wikipedia.org/wiki/Chlorhexidine
https://en.wikipedia.org/wiki/Bacteriostatic_agent
https://en.wikipedia.org/wiki/Savlon
Discussion:
The active ingredient in Savlon is chlorhexidine. Chlorhexidine is used as a disinfectant and an antiseptic. Savlon is bacteriostatic meaning that it prevents the growth and reproduction of bacteria. bacteriostatic disinfectants work by interupting the growth and reproduction cycle. They do this by interfering with the protein growth within the cell and also the DNA replication. By doing this the cell is not able to create offspring because they are unable to pass on their DNA.
Bacteria is made up of a capsule, cell wall, cell membrane, chromosome, plasmids, ribosomes, pili and a flagellum. The capsule helps keep the cell safe, the cell wall holds the structure of the cell, the cell membrane controls the nutrition and excretion of the cell, the chromosome hold the DNA of the cell, the plasmids hold extra DNA, the ribosomes are where protein is produced, the pili is used for transferring DNA between cells and the flagellum is used to move the cell. Since the cell membrane is what controls what comes in and out this means that the disinfectant breaks through the Cell wall, enters through the cell membrane and destroys the Chromosome which holds the DNA making the Bacteria cell unable to reproduce. Bacteria cells excrete and gain nutrition through their cell membranes. They do this by using active or passive transport.
Bacteria grow by replicating the DNA of the parent cell, after this they grow/elongate, after this stage they then split into two seperate cells and the reproduction cycle is complete. Bacteria reproduce very rapidly as they split into two from every parent cell. This means that the Bacteria is asexual. Since the Bacteria is self producing, when one Bacteria's DNA is destroyed there is no way for any more Bacteria to be reproduced from that certain cell. When the disinfectant is spread through a whole colony all of those Bacteria are rendered unable to reproduce. Passive transport is when there is a high concentration of molecules outside of the cell and a low concentration inside and the cell naturally diffuses the high concentration inside of the cell. Active transport is when there is a low concentration outside of the cell and a high concentration inside and the cell has to use energy to transport the molecules. So when a disinfectant is introduced to a bacteria cell it will enter the passive transport cycle and naturally diffuse into cell causing the chromosome to be destroyed.
Evaluation:
The Method we used was very effective, they were easy to follow and nothing went wrong. The method was reliable as the size of the clear zone varied because of the different concentration which is what we wanted. The size of the clear zones from each concentration on the different agars differed slightly but they remained relatively close. The averages are probably a little close together which could come down to not enough time letting the bacteria grow or putting to much Savlon on the filter paper resulting in the results not being extremely varied.
Research:
https://en.wikipedia.org/wiki/Chlorhexidine
https://en.wikipedia.org/wiki/Bacteriostatic_agent
https://en.wikipedia.org/wiki/Savlon
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