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Natural Science 161 - Health Science I

Course Goal: Acquire a general familiarity with the principles of Microbiology in order to understand the role of microorganisms in pathology and to understand the principles behind and execution of a Gram stain.


Homework Preparation for Online Class:

  • Read the section in Chapter 4 on the Cell Wall, pgs. 50–65 in ‘Principles of Microbiology’, by Tortora, Funk and Case, 10th Edition by Pearson Publishers. This will explain the science behind the Gram stain and why it is so useful to us.
  • View the PowerPoint slides for that section of the chapter, as a review of what you just read in Course Documents; when present depress ‘Click and CTRL’ (simultaneously) to see ANIMATION sections in the slides.

Online Class:

Write a post (new thread) on the DISCUSSION BOARD under the topic GRAM STAIN. Answer the following questions:

  • Which is Penicillin effective against -– Gram-positive cells or Gram-negative cells?
  • What are the differences between the two cell walls (Gram + and Gram -)?
  • Which of the cells walls has techoic acid?
  • Which of the cells walls has an extra layer of LPS (lipopolysaccharide)?
  • Which of the cells has Lipid A -– an endotoxin?

POST by midnight on Tuesday, April 6.

  • Read and respond to at least three of your classmates. Look to see if their answers are correct. If not, explain what they did wrong. POST responses by midnight on Friday, April 9.


Read Exercise #5 in your lab book: ‘Microbiology Lab for NVCC Woodbridge’ in preparation for next weeks lab session on Wednesday, April 7. You will read about the technique and materials used and will be ready to do your own Gram stain in lab.

In Class

Wednesday, April 7
Microbiology Lab
Exercise #5 - Gram Stain

  • Read through the procedure again, and I will review it with the class.
  • The material will be pointed out to you and found in the back of the lab.
  • Each student will be performing the Gram stain on the bacteria made available to you.

Homework “Food for Thought” Scenario:

A patient walks into the emergency room where you work. He has a terrible cough that is deep and productive of sputum (thick mucus from the lungs vs saliva which is thin and from the mouth). The working diagnosis is pneumonia. What’s a quick way to determine what, if any, antibiotic is needed? As you’ll see in lab, a Gram stain takes less than 15 minutes to perform.

Alice Weisz