Lab 11: Bacteria of the Skin
Learning Objectives:
• Identify the growth of skin bacteria on different types of selective and differential media.
• Identify pathogenic from non-pathogenic bacteria
Introduction:
Our skin forms the first line of defense. It has several characteristics that makes it an inhospitable environment for the growth of most microbes. Some of
these characteristics of skin include: high percentage of salt, low pH from 4-5.5, sebum, antimicrobial chemicals; an outer layer of dead skin cells that acts
as a barrier to pathogens; mechanical defenses such as continuous sloughing off of skin, and dendritic macrophages. Skin also harbors a range of resident
microbiota including Staphylococcus and Diptheriae species that act as normal antagonist microbiota….. Continue
Materials:
MSA plates, nutrient agar plates, sterile water, sterile swabs, marker, ruler, pure cultures of B. subtilis, E. coli, S. marcescens and S. epidermidis, inoculating
loops, incinerators
Method:
1. For this experiment, you will work in a team of 4 students.
2. Obtain two MSA plates and two nutrient agar plates per team.
3. Take one MSA plate and divide it in four parts.
4. Label each quadrant correctly with the name of the bacteria. Don’t forget to write initials of your names on each plate.
5. For the given broth cultures, use aseptic technique and streak bacteria on the plate appropriately as labeled.
6. Take the second MSA plate and divide it in three parts. Label each part correctly with the name of the bacteria.
7. Swab your skin and streak the appropriate area.
8. Repeat the above listed steps for the two nutrient agar plates.
9. Incubate the plates at 37◦C overnight.
10. Observe the sealed plate for growth and record your observations in the lab report and answer all questions.
11. Once observation is completed, immediately put the plates in appropriate waste container for autoclaving.
Lab Report:
Purpose: Describe the purpose of this lab.
Results:
Source of Skin inoculum:_____
Questions
Learning Objectives:
• Identify the growth of skin bacteria on different types of selective and differential media.
• Identify pathogenic from non-pathogenic bacteria
Introduction:
Our skin forms the first line of defense. It has several characteristics that makes it an inhospitable environment for the growth of most microbes. Some of
these characteristics of skin include: high percentage of salt, low pH from 4-5.5, sebum, antimicrobial chemicals; an outer layer of dead skin cells that acts
as a barrier to pathogens; mechanical defenses such as continuous sloughing off of skin, and dendritic macrophages. Skin also harbors a range of resident
microbiota including Staphylococcus and Diptheriae species that act as normal antagonist microbiota….. Continue
Materials:
MSA plates, nutrient agar plates, sterile water, sterile swabs, marker, ruler, pure cultures of B. subtilis, E. coli, S. marcescens and S. epidermidis, inoculating
loops, incinerators
Method:
1. For this experiment, you will work in a team of 4 students.
2. Obtain two MSA plates and two nutrient agar plates per team.
3. Take one MSA plate and divide it in four parts.
4. Label each quadrant correctly with the name of the bacteria. Don’t forget to write initials of your names on each plate.
5. For the given broth cultures, use aseptic technique and streak bacteria on the plate appropriately as labeled.
6. Take the second MSA plate and divide it in three parts. Label each part correctly with the name of the bacteria.
7. Swab your skin and streak the appropriate area.
8. Repeat the above listed steps for the two nutrient agar plates.
9. Incubate the plates at 37◦C overnight.
10. Observe the sealed plate for growth and record your observations in the lab report and answer all questions.
11. Once observation is completed, immediately put the plates in appropriate waste container for autoclaving.
Lab Report:
Purpose: Describe the purpose of this lab.
Results:
Source of Skin inoculum:_____
Questions
