Investigating Biological Spread Essay Sample

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Aim: To design and perform an experiment that will show the difference between microbial growth after washing and not washing your hands.


* 8 Sterile Agar plates

* Standard soap

* Sterile paper towel

* A growth medium

Method: Eight agar plates filled with a sterile growth medium had lines drawn down the middle of the lid and a ‘W’ and a ‘U’ were drawn at the top, standing for washed and unwashed. Seven students were then asked to press three fingers into the ‘W’ side of an agar plate. The students then washed their hands thoroughly with standard soap and dried their hands with sterile paper towels. The unwashed ‘U’ side of the agar plates then also had three fingers pressed into it the same way as before. All seven agar plates and one agar plate that hadn’t been touched were left in an incubator for a week at 35?C. The results found were then researched using the Internet to find out what the different microbes were.

Results: The experiment has shown that even washing your hands doesn’t kill all microbes as seen in all agar plates except number two. This means that the experiment wasn’t conclusive however it did provide some useful information. Most of the microbes that survived the hand washing were large colonies of fungi. The control used to stop pathogens and/or contamination had to be strict while conducting the experiment and these measures were that the lids were only taken off for the shortest possible amount of time and no one was to breath on the plates. The agar plate that wasn’t touched during the process grew some microbes.


Discussion: The experiment has been a success in determining whether washing hands helps to kill bacteria and fungi. It was clear from agar plates four, five and six that some germs and fungi are resistant to soap, this could be due to natural selection which could happen when people don’t wash their hands properly and the strongest germs survive and reproduce to make a new stronger generation. However it could also be due to human error if someone didn’t wash their hands properly or someone breathed on the agar plate and it became contaminated.

From this experiment it is possible to draw the conclusion that fungi grows more rapidly if it doesn’t have to compete with other organisms. This can be seen in agar plate number four, five, seven and three where no fungi can be seen in the unwashed section yet in the washed section with no other competitors it thrives.

The most frequently found microbe on the unwashed side of the agar plate was the staph, however on all of the plates except number four, the staph were either killed or significantly slowed down. One explanation for number four to be the only one to still have a significant number of staph after washing is that it is a different or stronger strain of staph.

It is clear that some contamination was present in all of the agar plates because the eighth plate was not opened, it was just left near the others while the experiment was carried out.

Conclusion: The experiment showed the difference between microbial growth when you wash and don’t wash your hands. However the results returned were not as expected as in some of the agar plates’, large quantities of microbes were found.

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