BIOLOGY 251L

MICROBIOLOGY

PRACTICUM 1 STUDY GUIDE

 

Your exam will cover everything from week 1 through week 6.  This is only a study guide.  Not all of the materials you’re responsible for are in this guide.  Go over your lab manual, lab reports, handouts, quizzes, and notes.

 

 

Week 1 covered Exercises 1 & 4

 

  1. Know the following terms: limit of resolution, parfocal lens system
  2. Know how to calculate the magnification of an object you’re viewing through the microscope.
  3. Know the parts of the Bright-field Light Microscope.
  4. Why do we use oil immersion for bacterial cultures?
  5. Know the three domain classification system.
  6. Know the different bacterial shapes and arrangement.
  7. These are the organisms you studied in week 1:

Micrococcus luteus-cocci, nonmotile, Brownian movement on live cultures

Bacillus anthracis non-motile & Bacillus subtilis-rod, motile

Nostoc-hetorocysts for N fixation

Saccharomyces cerevisiae-yeast reproduces by budding/binary fission

Amoeba proteus-pseudopodia, cytoplasmic streaming

Euglena-green cells

Paramecium-move by cilia

  1. Be able to recognize organisms under the microscope.  Be aware of specific structures (presence or absence of a nucleus, etc.)
  2. What’s the difference between a Bright-field Light Microscope and a Phase-Contrast Microscope?

 

 

Week 2 covered Exercises 13 & 14

 

  1. What are the three physical forms of media?
  2. Know the differences between the types of media we discussed (i.e. chemically defined vs. complex).
  3. What is sterilization?  What are some of the ways we sterilize media and materials?
  4. What is subculturing?  What is the purpose of subculturing?
  5. Why is aseptic technique important in lab?
  6. What are some of the methods we can use to maintain pure cultures?
  7. You studied Serratia marcescens in week 2.  What specific characteristic does this organism has that makes it easy to identify?

 

 

Week 3 covered Exercises 7, 16, & 15

 

  1. What is a bacterial smear?  What is the difference between preparing a bacterial smear from a both culture and a solid medium?
  2. Why do we have to heat-fix our bacterial smears?
  3. What is simple staining? What is its purpose?  What’s the difference between acidic and basic dyes? How does each one work?
  4. Be able to recognize the kind of stain used on a slide of specimen (crystal violet, methylene blue, carbolfuchsin)
  5. What’s the purpose of the streak-plate and spread-plate techniques?
  6. Be able to demonstrate a streak-plate on the exam.
  7. What is a colony?
  8. The organisms you studied in week 3 are: Serratia marcescens, Micrococcus luteus, Rhodospirillum rubrum, Escherichia coli, Bacillus subtilis. 

 

Week 4 covered Exercises 8, 10, 14 (part 2), & 15 (colony characteristics)

 

  1. What type of stain is the Gram stain?  What are the reagents we use?
  2. Why do we use a mordant on the Gram stain?  Know what each reagent does.
  3. Know the Gram stain procedure and how it works.
  4. What does it mean to be gram variable?
  5. What type of stain is the endospore stain?  What is an endospore?
  6. Why do we use heat in the endospore stain?
  7. What is the medical significance of the endospore stain?
  8. Know the endospore stain procedure.

9.  The organisms you worked with in week 4 are: Escherichia coli (gram – rods, not an endosporeformer), Staphylococcus epidermidis (gram + cocci), Bacillus subtilis (rod, endosporeformer), Clostridium sporogenes ( short rod with a central spore)

 

Week 5 covered Exercises  9, 11, 18

 

  1. What type of stain is the acid-fast stain?  Why do we use this stain on certain bacteria?  What is unique about acid-fast organisms? Hint: characteristic of their cell wall
  2. What is the medical significance of this stain? 
  3. Know the acid-fast stain procedure.  Why do we use heat?
  4. What is a capsule?  Why are capsules important to bacterial cells?
  5. How does the capsule staining works? Hint: it’s a negative stain

6.   What are some of the mechanisms motile bacteria use to self propel?

  1. What is Brownian movement and what causes it?
  2. Know the following bacterial characteristics: obligate aerobes, facultative anaerobes, obligate anaerobes, aerotolerant anaerobes, microaerophiles.
  3. What are some of the ways we can determine the oxygen requirement of microorganisms?
  4. The organisms you studied in week 5 are:  Mycobacterium tuberculosis (acid-fast bacterium), Klebsiella pneumoniae (a bacterium with a capsule), Proteus vulgaris (motile, facultative anaerobe), Bacillus subtilis ( motile, obligate aerobe), Micrococcus luteus (nonmotile, obligate aerobe), Staphylococcus epidermidis (nonmotile, facultative anaerobe), Clostridium sporogenes (obligate anaerobe), Escherichia coli (facultative anaerobe)
  5. Be able to recognize ALL of the organisms mentioned in this guide on a slide under a microscope, on a plate, in a tube.  Know their patterns of growth in different types of media.

 

Week 6 covered Exercises 19 & 45

 

  1. What’s the difference between the standard or viable plate count method and the spectrophotometric (turbidemetric) analysis?  What is their purpose?
  2. Be able to recognize and work through a dilution problem.  Know how to calculate the CFU/ml.  What does CFU stand for and what is the concept behind it?
  3. What are the four phases of bacterial growth?  What are the differences between them?
  4. Be able to calculate the generation time from a growth curve. 

 

 

REMINDERS:  You have to know both names of the organism and underline it.  Go through the demos.

 

 

GOOD LUCK!! 

 

 

* See your lab manual appendix for more dilution problems they have answers.