MB 6200 L06 Growth Microorganisms-1 PDF

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Growth of Microorganisms PRE-LAB QUESTIONS 1. Why don’t microorganisms in cultures exhibit constant exponential growth? What are some steps you could take to extend the lifespan of a microbial culture? Microorganisms in culture exhibits don’t constant exponential growth because they are unexposed to oxygen, have limited space to grow and limited nutrients. To extend the lifespan of the microbial culture they would need a larger culture or a new culture every so often.

2. Using a textbook or a reputable online source, describe how lab cultures are maintained in a continual pattern of growth. Focus particularly on those used in biotechnology, such as E. coli, which is used to make human insulin. Scientists can use chemostats or turbidostats to allow continual growth in lab cultures. They regulate nutrients and waste. 3. Which of these has a constant growth pattern: an open system or a closed system? An open system has a constant growth pattern. An open system can remove dead cells and provide constant nutrition. 4. A human patient represents what kind of system for bacterial infections? Humans represent an open system. 5. You’re a physician trying to isolate bacterial colonies from the human gut in attempt to diagnose a gastrointestinal infection. You streak your sample on a growth media containing glucose, amino acids, and salts that contain both sulfur and phosphorous with a pH of 7. You incubate the plates in aerobic conditions at 37 ˚C for three days, at which point you can see clear bacterial colonies forming on the plate. Would you feel confident in stating that you had successfully cultured all the bacteria from your gut sample? Why or why not? I would feel confident that I had cultured the bacteria from the gut sample because there was bacterial growth happening.

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Growth of Microorganisms EXPERIMENT 1: FLUID THIOGLYCOLLATE MEDIUM TO ASSESS THE EFFECT OF OXYGEN ON BACTERIAL GROWTH Data Tables Table 1: Experiment 1 Results Sample

Growth Location in FTM

Oxygen Category

Skin

Minimal

Facultative

Nose

1.5” from bottom

Aerotolerant or anerobic

Throat

Minimal

Facultative

Shoe

Throughout tube

Aerotolerant or anerobic

Control

Minimal

Facultative

Post-Lab Questions 1. What does the pink band in the FTM indicate?

Where the oxygen is present.

2. What would be the effect of using FTM tubes with a broad pink zone?

To understand what kind of bacteria grows best with and without oxygen.

3. Provide an explanation as to why bacteria from each location displayed their pattern of growth. Are there any results that surprise you? If so, why?

The shoe and nose samples were able to grow despite the lack of oxygen.

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Growth of Microorganisms 4. Why is it important to pull the inoculating needle out of the FTM via the same path you inserted it?

To be sure you get an accurate sample. You do not want to allow too much oxygen or other things to enter into the sample.

5. Why was it necessary to have separate controls for the agar plates and the FTM tubes?

To understand how things look when there is no bacteria present, to have something to compare the others to.

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Growth of Microorganisms EXPERIMENT 2: EFFECT OF CHEMICAL GERMICIDES ON BACTERIAL GROWTH Data Tables Table 2: Experiment 2 Results Sample

Germicide

Zone of Inhibition (mm)

Skin

10% Bleach

2.6mm

Skin

70% Isopropyl Alcohol

2.6mm

Skin

Hibiclens®

2.6mm

Skin

Deionized Water (Control)

2.6mm

Nose

10% Bleach

2.6mm

Nose

70% Isopropyl Alcohol

2.6mm

Nose

Hibiclens®

2.6mm

Nose

Deionized Water (Control)

2.6mm

Throat

10% Bleach

2,6mm

Throat

70% Isopropyl Alcohol

2.6mm

Throat

Hibiclens®

2.6mm

Throat

Deionized Water (Control)

2.3mm

Shoe

10% Bleach

2.6mm

Shoe

70% Isopropyl Alcohol

2.3mm

Shoe

Hibiclens®

2.6mm

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Growth of Microorganisms Sample

Germicide

Zone of Inhibition (mm)

Shoe

Deionized Water (Control)

2.3mm

Post-Lab Questions 1. Which germicide was most effective for each sample? Was the same germicide the most effective for microorganisms isolated from the different sources? What could explain this similarity or difference?

I, unfortunately, did not have much of a range in my samples. There was growth only on the shoe sample in the control and the alcohol portions. This leads me to believe that bleach and hibiclens are more effective germicides.

2. Which germicide was least effective? Was the same germicide the least effective for microorganisms isolated from the different sources? What could explain this similarity or difference?

It seems as though the alcohol and the control were the least effective germicides in the one sample that had growth on it.

3. Were any of the cultured microorganisms particularly resistant to the germicides tested? If so, which culture? What could explain this strong resistance?

No, I had very minimal growth in my lawn plates.

4. Why was it necessary to dip one of the filter paper pieces in deionized water?

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Growth of Microorganisms To have a control to compare the other germicides to.

5. Look up the chemical formulas for bleach, isopropyl alcohol, and chlorhexidine gluconate (the active ingredient in Hibiclens®). How does each chemical achieve its germicidal properties on the molecular level?

Bleach: NaClO oxidizes molecules in the cells and kills them.

Alcohol: C3H8O denatures the cell. The cell’s wall loses it’s intergral structure.

Hibeclins: C22H30Cl2N10 destabilizes the cell wall and interferes with osmosis. Once the cell wall is down it attacks the cell membrane.

6. What are some real-world applications for a study like this? For instance, how would these results influence cleaning practices in a doctor’s office or treatment of a disease?

A doctor’s office is a great example of where these cleaning products should be tested and considered differently. It is important to use germicides that properly kill bacteria to prevent the transfer of bacteria to a new patient.

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