Growth Microorganisms - Lab 6 PDF

Preview

Summary

lab 6...

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 do not exhibit constant exponential growth because they grow on the medium. They may run out of nutrients, become poisoned by too much waste being built up or because the PH levels have been altered. You could try to extend the lifespan of a microbial culture by adding more nutrients to the medium or possibly transferring the bacteria to a new plate.

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.



Lab cultures are maintained in a continual pattern of growth with a device called a chemostat. This continuously supplies new medium that limits an essential nutrient, allows bacterial growth, and removes bacterial cell 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 due to being able to provide unlimited nutrients, while a closed system has limited nutrients and microbes will no longer be able to grow.

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

©eScience Labs, 2018

Growth of Microorganisms 

A human patient is continuously removing waste and providing ourselves with nutrients. We represent an open system, providing a perfect place for a bacterial infection to grow.

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 in stating that I had successfully cultured all the bacteria from the gut sample. I would not feel confident because there is oxygen that has been applied to my sample, and there could be anaerobic bacteria that is causing issues in the stomach. These anaerobic bacteria may not show up due to the aerobic experimental setting.

©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

On top of the surface

Obligate aerobes

Nose

More on the surface, but also throughout the tube

Facultative anaerobes

Throat

Throughout the tube

Aerotolerant anaerobes

Shoe

More on the surface, but also throughout the tube

Facultative anaerobes

Control

Nothing

Nothing

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



The pink band in the FTM indicates that there is oxygen present.

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



Anaerobes would be affected using FTM tubes with a broad pink zone. Aerotolerant anaerobes would still be able to grow regardless of the broad pink zone.

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 grew on the surface indicating it was obligate aerobes. The nose and shoe bacteria grew on the surface and throughout the tube, indicating they were facultative anaerobes. The throat bacteria grew throughout the tube indicating it was aerotolerant anaerobes. I was surprised that the nose and throat were not obligated aerobes, since they are part of our respiratory system and figured would need high oxygen to survive.

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



It is important to pull the inoculating needle out of the FTM via the same path as you inserted it to minimize the amount of oxygen.

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



It is necessary to have a separate control for the agar plates and the FTM tubes to make sure that I am using the proper techniques and that nothing was 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

6

Skin

Hibiclens®

3

Skin

Deionized Water (Control)

0

Nose

10% Bleach

10

Nose

70% Isopropyl Alcohol

4

Nose

Hibiclens®

0

Nose

Deionized Water (Control)

0

Throat

10% Bleach

10

Throat

70% Isopropyl Alcohol

4

Throat

Hibiclens®

2

Throat

Deionized Water (Control)

0

Shoe

10% Bleach

11

Shoe

70% Isopropyl Alcohol

8

Shoe

Hibiclens®

6

©eScience Labs, 2018

Growth of Microorganisms Sample

Germicide

Zone of Inhibition (mm)

Shoe

Deionized Water (Control)

none

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?



For my experiment, the most effective germicide was 10% bleach. I believe this was because all the samples came from the body, being the similar source of environment.

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?



For my experiment, Hibiclens was the least effective germicide. There was little to no effect for controlling growth. This could be because it is used to cleanse the skin.

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



Cultured microorganisms from my nose were particularly resistant to the germicides tested. This could be because they are more resistant to antibiotics.

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

©eScience Labs, 2018

Growth of Microorganisms 

It was necessary to dip on of the filter paper pieces in deionized water to use as a control. This makes sure the results are accurate and should not be affected by the growth.

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’s chemical formula has sodium hypochlorite which causes unfolding of the proteins in bacteria. Isopropyl alcohol kills bacteria, fungi, viruses, uncapable of killing spores. Chlorhexidine gluconate disrupts the membrane and kills the bacteria.

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?



This study helps us see how cleaning and disinfecting with what products kill certain bacteria. It is especially important to do so to help stop the spread of bacteria and provide the safest and cleanest environment for patients, especially those who are immunocompromised.

©eScience Labs, 2018...