Garlic and mint core practical – investigating the antibacterial properties of plants
Introduction
Plants are susceptible to infections by bacteria and fungi; they do everything to repel one another. Several plants are known to or even thought to inhibit the growth of certain bacteria. A plant with such properties is known as an antibacterial. Chemicals within them are toxic to bacteria and interfere with the metabolism in some way. In order to protect themselves they produce anti-bacterial and anti-fungi agents. Garlic is said to be used to treat infections with bacteria, yeast, fungi, and parasites, and can be used to treat high blood sugar levels. They also say it has properties that may help stomach and abdominal problems. The use of garlic has also been claimed to reduce risk of heart disease, lower serum cholesterol, and reduce blood pressure.
Aim
The aim of this experiment is to investigate the antibacterial properties of plants (garlic, mint, and methylated spirit) and to develop a certain experiment skills.
Hypothesis
My hypothesis is that garlic will be least affected by the bacteria as it will be able to protect itself whereas, the methylated spirit and the mint will be more susceptible to it.
Variables
Controlled variable: temperature and the time
Dependant variable: the bacteria
In order to ensure the experiment is fair I will be using the same amount of each substance I will also be using the same temperature and the same amount of time. The temperature must remain at 25 degrees when the Petri dishes are put into the incubator, as this is the optimum temperature and anything above it may create inaccurate results.
Size of paper disk-the bigger the paper disk the more anti-bacterial cells that it will contain, therefore there will be a larger clear area around the disk. This will need to inaccuracy, and I will not be able to determine whether the mint or the garlic has the most resistance to bacteria.
Amount of bacteria used-I will need to make sure that the bacterium is spread evenly across the whole agar plate. If there is a denser area of bacteria this will affect the size of the clear area and will lead to inaccuracy.
Plant Extract-make sure that plant extract is taken from the same plant.
Time-I will need to ensure that the agar plates remain in the 25°C incubator for 24 hours.
Equipment
Agar plate seeded with bacteria – this will be a key component in the experiment while testing the plants as they will be used to see the affect it has
Plant material – the garlic and mint leaves – these are the plants I will be using to test for bacteria
Sterile pipette this will allow me to precisely measure the two antibacterial.
Paper disks – this will allow me to get hold of the garlic from the Petri dish
2 sterile Petri dishes – the Petri dishes will give me a good sample of the surface area needed to test the plant. Other than this it is transparent so I can see what is happening inside
3 sterile forceps-the forceps will allow me to pick the bits of garlic and mint to see my results
Tape – the tape it is important as it not only will secure the Petri dish but will also be applied in a cross because any excluded air that will encourage the risk of anaerobic bacteria from being formed which will release pathogens that can potentially cause diseases. Hence by taping it in this way we prevent this from happening.
Marker pens – the marker pens will be used to label the Petri dish in order for us to identify where the garlic and mint is.
Incubator set at 25 degrees – the incubator will be set at this temperature when the Petri dishes are complete and will be put inside it. This is the optimum temperature for them to be in.
Bunsen burner – the Bunsen burner will be used to flame the neck of the ecolyte to get rid of any bacteria.
Ecolyte – the antibacterial that will be used in the experiment
Pestle and mortar – this will be used to crush the garlic and mint
White tile – the tile will be used to place the garlic on and the paper disks to make it easily visible.
Method
- Follow the full sterile technique to avoid any hazards. Wash your hand with the antibacterial hand wash. Then clean the bench area you will be working on with a disinfectant.
2. Firstly you will find that the agar plate has already been pre-prepared for you and seeded with bacteria.
3. Add 3g of the chosen plant was crushed with 10 cm of Methylated sprit. This is used to kill any bacteria. The mixture would have to shaken regularly.
4. Then using a pipette 0.1cm 3 of the extract was put onto the sterile paper and would be left to dry for 10 minutes on open sterile Petri dishes.
5. This would be repeated but changing the plant extract, so leaving you with three filter paper discs.
6. Using the sterile forceps the discs will be placed on the bacterial plate. Each Petri dish will be clearly labelled using a marker. When the Petri dishes was not in use they were not opened because excess bacteria will enter the dish meaning the experiment would not be successful and the results would be unreliable.
7. The Petri dish would then be taped shut in the same technique making a cross on top and bottom. And would then be left incubated for 24 hours at 25 C
8. The plates would then be observed and measurements would be taken.
Safety
· To ensure safety I will be using sterile technique-before beginning the experiment I washed my hands with antibacterial hand wash and cleaned the bench area with the a disinfectant.
· When opening the Petri dish I held the lid above to minimise the risk of contamination of air born bacteria and dust.
· At the end when the agar was setting in place I put the lid slightly to one side to allow the condensation to escape. If this were not done condensation would have built up inside the Petri dish and distorted my results.
· Aseptic techniques- whenever the lid is of the bottle is removed, you need to flame the neck of the bottle to ensure that any germs or bacteria are destroyed, before screwing the lid back on.
· Methylated Spirits-are toxic and highly flammable. Therefore when the aseptic technique is applied, be sure to keep away from Bunsen burner. Also it’s toxic, so it must not be consumed or inhaled.
· At the end I taped the dish in a cross as shown in the diagram below:
·
The reason for this is that by doing we excluded any air. To prevent the risk of the growth of anaerobic bacteria which is pathogenic and could be the cause of the development of a disease.
Mint / 7,0,0,0,0,0 / 1.16
Garlic / 22,0,22,21,11.13 / 14.83
Control / 12,8,15,3,9,8 / 9.16
Conclusion:
The above results illustrate that
1. The anti microbial is garlic as the average was 14.38.
2. The mint had the weakest anti microbial effect.
Hence it can be concluded that my hypothesis was correct, as the results I have obtained are reflective of this. My results show that the bacteria least affected garlic; therefore this shows that it had greater anti bacterial properties making it more resistant to the bacteria. The mint was the weakest showing that it had no antibacterial properties making it much more susceptible.
Evaluation:
The results I have found are accurate, as they have been replicated. However, the reliability of my data is good as they are all close together. I believe that many factors may have contributed to the inaccurate results formed:
1. A wide range of data of results were used which were obtained from the whole of the class. For mint there seems to be an obvious anonymous result as one of the six groups that conducted the experiment got a 7mm clear ring while the rest got 0mm.
2. This may have occurred due to the Petri dish being left fully open allowing anaerobic conditions to develop and affecting the end result of the experiment. However improvements could be made. To get some results I could have used a venire calliper, which is accurate to 0.1mm.
3. Another cause of inaccuracy was time as when the plant material was crushed with 10cm3 of Methylated spirit it had to be kept in there for 10 minutes.
4. Also when another error, which may have resulted in unreliable results, was the collecting of the mint, more care could have been taken whilst doing so to ensure that only the leaves of the mint plant were taken. This is because while carrying out our experiment there were a few parts of a stem that were crushed with the plant extract.
If I were to carry out this experiment again, I would use larger paper disks, so that there was a larger surface area for the anti-bacterial cells to repel against the bacteria. This would therefore create better and measurable results, from which I could confidently conclude whether the garlic or the mint is better.