Lab 6 - microbiology lab assignment PDF

Preview

Summary

microbiology lab assignment...

Description

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 cultures are not able to exhibit constant exponential growth because they consume all the nutrients provided in the media, or either the pH no longer supports their growth and also, the waste may be becomes a poison to them.

I would transfer the microorganisms to another plate with fresh growth media.

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.

-Continual pattern of growth of lab cultures can be maintained through use of devices like chemostat, where fresh medium is continuously supplied into growth chamber at a rate that limit the growth of bacteria. It also allows the bacteria to grow at the same rate that bacteria cells are removed by the overflow.

3. Which of these has a constant growth pattern: an open system or a closed system?

-An open system because it provides unlimited nutrients allowing the microbes to grow constantly.

©eScience Labs, 2018

Growth of Microorganisms

4. A human patient represents what kind of system for bacterial infections?

-

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?

No. I would not feel confident because the only bacteria that will grow are aerobes, meaning that the patient could be having infection due to anaerobic bacteria which in this experiment will not grow.

©eScience Labs, 2018

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

top

Obligate aerobes

Nose

Throughout the tube, but more concentrated at the tube

Facultative anaerobes

Throat

Throughout the tube

Aerotolerant anaerobes

Shoe

Throughout the tube, more concentrated at the top

Facultative anaerobes

Control

none

none

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

-The pink band indicates presence of oxygen

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

-it would make it harder for anaerobes to grow except for aerotolerant anaerobes which can grow regardless of oxygen concentration.

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?

©eScience Labs, 2018

Growth of Microorganisms -The skin bacteria displayed their pattern of growth on the top of the tube, meaning that they are obligate aerobes which grow only in presence of high oxygen. Bacteria in nose, and shoe were present throughout the tube but concentrated on the top area, meaning that they are facultative anaerobes which can thrive in presence of oxygen but also can grow in its absence. Bacteria in throat displayed their pattern throughout in the tube meaning that they are aerotolerant anaerobes.

These results surprised me because I expected throat and nose bacteria to be obligate aerobes because they are in our respiratory system.

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

-To minimize amount of oxygen exposed into the medium

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

6. Because they both need to have separate control for each procedure. For agar plate we want to make sure that agar and cotton swab are not contaminated, and for the FGM tube, tube and sterile inoculating needle are not contaminated.

©eScience Labs, 2018

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

14

Skin

70% Isopropyl Alcohol

5

Skin

Hibiclens®

3

Skin

Deionized Water (Control)

0

Nose

10% Bleach

9

Nose

70% Isopropyl Alcohol

3

Nose

Hibiclens®

0

Nose

Deionized Water (Control)

0

Throat

10% Bleach

9

Throat

70% Isopropyl Alcohol

5

Throat

Hibiclens®

2

Throat

Deionized Water (Control)

0

Shoe

10% Bleach

10

Shoe

70% Isopropyl Alcohol

7

Shoe

Hibiclens®

2

©eScience Labs, 2018

Growth of Microorganisms Sample

Germicide

Zone of Inhibition (mm)

Shoe

Deionized Water (Control)

0

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?

-According to my plates,10% Bleach was most effective germicide. Yes similar results were obtained in all samples because they were obtained from same body.

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?

-According to my plates, Hibiclens was least effective germicide for all samples, especially nose. There was no effect of controlling growth in nose and little effects on throat. Probably because Hibiclens are normally used for general external skin and mouth cleansing.

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

Microorganisms found in nose seemed to be the most resistant to germicide. Alcohol had no effect on controlling growth, bleach and Hibiclens had a little effect.

©eScience Labs, 2018

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

Filter paper in deionized water was used as negative control to ensure test results are accurate. 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 -NaOCL (sodium hypochlorite). Hypochlorite, works similar to heat stress, causing denature of the proteins to clump together.

Isopropyl alcohol-C3H8O, dimethyl carbine. When bacteria cell is exposed to isopropyl alcohol, the amphiphile alcohol molecules bond with the molecule of the bacteria cell membrane making it more soluble in water. This causes the cell membrane to lose its structural integrity and fall apart. Alcohol molecules enter the cell then begin to dissolve the proteins through denaturation.

Hibiclens-C22H30CL2N10 (chlorhexidine gluconate). It destabilizes the cell wall and interferes with osmosis damaging the cell wall. Then chlorhexidine crosses into the cell itself and attacks the inner membrane, leading to cell death.

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?

©eScience Labs, 2018

Growth of Microorganisms -This will help to determine the effective germicide in different environments, and how much it can eliminate growth of different types of bacteria growing in different environment.

©eScience Labs, 2018...