Sheila M. Martin-Corbin
Introduction:
Antibiotics and ribosomes: Inhibitors of protein synthesis
Both bacteria and human cells possess similar cell organelle, ribosome, for protein synthesis. However, bacterial and eukaryotic cells have ribosomes which are different in structure in regards to their molecular weight and shape. This difference allows antibiotics the ability to specifically target one type of cell and not the other.
Tetracycline, an antibiotic, inhibits bacterial growth by stopping protein synthesis on ribosome. This antibiotic is capable of accumulating in high concentrations in the cytoplasm of bacterial cells. However, in human cells, tetracycline does not accumulate in such concentrations to stop protein synthesis.
Antibiotics bind to subunits at specific sites on the ribosomes, preventing the attachment of tRNA, and halting the growth of the polypeptide chain.
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Germs are all around us. These microorganisms can be found on many different surfaces such as door knobs, computer mouse, cell phone, desktops, tables to name a few, which are culprits for causing a person to become sick.
For this reason, we need to control and/or minimize the number of microbes around us in an effort to diminish our chances of becoming ill.
Objective:
Students will test different household substances to see which one kills the most bacteria on the surface of their desks. Students will grow colonies of bacteria on agar plates, which provides food and vitamins for bacterial growth. Prior to collecting bacteria cultures, the surface of the desks should be cleaned with the different disinfectants including water.
Materials:
Disinfectants
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Lysol spray
10% Bleach solution
70% Rubbing alcohol
Distilled water
Safety eye goggles
Disposable gloves
Nutrient agar plates
Masking tape
Table/desk tops
Cotton balls
Permanent marker
Sterile cotton tipped applicator
Tweezers
Small plastic cups for disinfectant
Procedure:
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Use masking tape to section off four equal squares on desk/table top. Number each square 1 through 4.
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With protective gear on, use cotton ball to cleanse each square with a different disinfectant. Be sure to control all variables. For example, use the same amount of each disinfectant to cleanse the designated area.
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Allow each area to air dry for a specified amount of time.
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Use a clean cotton swab to obtain bacterial culture from each square onto corresponding marked nutrient agar plate. (Distilled water will be used as a negative control).
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Be sure not to let the tips of the cotton swab to contact or contaminate any other section of the desk top during the application process.
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Carefully replace lids on agar plates and place in an incubator or warm place at room temperature for 1-2 days.
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Observe any growth of bacterial colonies on agar plates.
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Count the number of bacteria colonies on each nutrient agar plate and record results and any other observations in the data table. Pictures may also be taken of the bacterial colonies for comparison.
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Graph the results and compare the activities observed of the different disinfectants resulting in growth or no growth of bacteria.
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Dispose of bacterial culture according to the teachers direction and be sure to wash your hands thoroughly after handling bacterial specimen and other materials used in this laboratory investigation.
Data Table
Petri dish #
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Name of disinfectant
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Number of bacteria colonies
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Observation
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