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How to handle bacteria, culture bacteria and observe the bacteria Essay

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.

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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.

Bacteria are one-celled organisms visible only through a microscope. Bacteria live all around us and within us. The air is filled with bacteria, and they have even entered outer space in spacecraft. Bacteria live in the deepest parts of the ocean and deep within Earth. Most bacteria are less than 1 micron (0.001 mm/0.00004 in) in length. However, colonies of bacteria, such as those found on a laboratory culture plate or on the surface of salt marsh mud, can be viewed easily without a microscope. A variety of classification systems are used to order bacteria. Bacteria are described as prokaryotes, organisms whose cells lack nuclei, to distinguish them from eukaryotes, organisms such as fungi, plants, and animals, whose cells contain nuclei. Bacteria are often classified on the basis of their physical shapes. Bacteria can be culture in three different medias in the laboratory. In solid medias (LB agar), liquid media (LB broth, nutrient broth, glucose broth etc.) and semisolid media (use to study the movement of bacteria). In these activities, we will use LB agar to culture our bacteria.

In order to study more about bacteria, we will collect samples, which are suspected to contain bacteria and culture it on LB agar. We will also test for the bacteria on our thumb before and after washing of hands. Thereafter, to observe the bacteria more closely and clearly, we will remove one colony from the plate and Gram stain it to observe it under the microscope.

Gram’s Stain is a widely used method of staining bacteria as an aid to their identification, devised by Hans Christian Joachim Gram, a Danish physician. This method help scientist to identify and characterize bacteria, as they are colourless and cannot be viewed under the microscope clearly. The bacteria will either retain the strong blue color of gentian violet or red. They can be identified as spherical (cocci), rod-shaped (bacilli), or corkscrew-shaped (spirochetes). The thickness of their cell wall and their arrangements can also be determined.

I expect to see bacteria growing on or near the streaked line on the LB agar and that the area where the thumb was pressed on the LB agar before washing would be more dense with bacteria than after washing of our hands with soap and drying them. As for the Gram’s staining, I expect to see the bacteria with different colours (e.g. blue, purple, red) revealing the thickness of their cell walls. The shape and arrangements of the bacteria would be visible under the microscope.

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