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The main aim in the life science lessons is to learn how to handle bacteria, culture bacteria and observe the bacteria.

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Introduction

Summary The main aim in the life science lessons is to learn how to handle bacteria, culture bacteria and observe the bacteria. My hypothesis is that the bacteria in the collected sample would grow on or near the streaked line on the LB agar and there would be fewer bacteria on our thumbs after washing our hands with soap and drying it as compared to before washing. As for the Gram's staining, the bacteria would be of different colours (e.g. blue, purple, red) revealing the thickness of their cell walls. Their shape and arrangements would also be visible under the microscope. In order to test our hypothesis, we had to collect samples, which were suspected to contain bacteria and culture it on LB agar. We also had to test for bacteria on our thumb before and after washing of hands. Thereafter, we had to observe the bacteria more closely and clearly by removing one colony from the plate and Gram staining it to observe it under the microscope. There were both positive and negative results to the experiment. The results for culturing bacteria from 2 collected sample showed some negative results due to contamination and the differences of the ph level between the LB agar and the sample (Vitagen and Yakult). The two other results (left over water and fish tank water) were positive and bacteria was seen growing on the line were the bacteria was streaked. The test for bacteria on the thumb before and after washing of hands also had some negative results for 2 samples due to a dirty cloth use to wipe the thumbs. The other two had positive results. The result for Microscopy (Gram's staining) was positive and the bacteria were stained with different colours (e.g. blue, purple, red) revealing the thickness of their cell walls. Their shapes and arrangements were also visible under the microscope. Introduction The main aim of the life science lessons is how to handling bacteria and how to culture them and observe them. ...read more.

Middle

Thereafter, using an inoculation loop, we aseptically transferred a tiny colony (petri dish 3, before section) to the glass slide and smear it within the marked circle. Thereafter, the glass slide passed through a Bunsen burner flame very quickly. This would kill the bacteria so that the staining would be successful. Staining bacteria- Firstly, we flooded the smear with Crystal violet solution for 1 minute. Next the glass slide was washed with water. Again, we flooded the smear with iodine solution for 30 seconds and washed with water. Thereafter, we flood the smear with ethanol (for about 3 seconds), until the violet coloration on the smear disappears. Finally, the smear is flooded with Safranin for 1 minute, rinsed off with water and blot dry with a paper towel. Microscopy-After the nose of the objective lens is rotated to the 4x objective lens and the glass slid is placed on the stage and secured by the stage clips, the stage is lifted up to the highest with the coarse adjustment knob. The power was then switched on and the light intensity is adjusted until comfortable to the eye. The course adjustment knob is adjusted again to obtain clearer image and the fine adjustment knob is adjusted to get a sharper image. The objective lens was rotated to10x and 40x objective lens to view the bacteria at a bigger magnification. Results These were the results for the culturing of bacteria. Petri Dish 1 Sample- Water from fish tank. Observations There were many colonies of bacteria growing on the line where the sample was streaked. The colonies were about 0.5 in diameter. There were also several confluent growths. As for the bacteria which was collected from the thumb, there were many small colonies and a big confluent growth in the center in the before section. There were also a few colonies of bacteria in the after section. ...read more.

Conclusion

The main reason to the problem was probably due to talking and sneezing while culturing the bacteria. Another problem in Petri Dish 3 and Petri Dish 4 was that the cloth used to wipe the thumbs probably had a lot of bacteria, which made the experiment an unfair one. The third problem is that the bacteria in petri Dish 3 and petri Dish 4 couldn't grow due to the LB agar being less acidic. Recommendations The biggest problem that was encountered was, contamination due to talking and sneezing during the experiment, which was extremely visible in Petri Dish 3 and Petri Dish 4 (culturing bacteria from sample). Another problem in Petri Dish 3 and Petri Dish 4 was that the cloth used to wipe the thumbs probably had a lot of bacteria, which made the experiment an unfair one. The third problem is that the bacteria in petri dish 3 and petri dish 4 couldn't grow due to the LB agar being less acidic. One good way, which I recommend to reduce contamination due to talking and sneezing during the experiment, is to use mouth mask that covers the mouth and nose. As for the problem about the dirty cloth used to wipe the thumbs, I recommend that clean paper towels should be used to wipe the thumbs dry so that the experiment is a fair one. Lastly, for the third problem, I recommend that a sample used should have a ph lever closer to that of LB agar. The Conclusion The main aim of the life science lessons is to learn to handle and culture bacteria and observe the bacteria. If the steps of the experiment were carefully followed, I can conclude that bacteria in the collected sample will grow on the streaked area (if there's no contamination and if the sample has a ph level not to far from LB agar), washing hands with soap can reduce bacteria (if the cloth used to wipe dry is clean) and Gram's staining would make the shape and arrangement of bacteria visible under the microscope as while as the thickness of their cell wall. ...read more.

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