Intro to microbiology

Question 1 of 12 2.0 Points

All of the following are considered microbes except A.viruses B.bacteria C.protozoa
Correct D.worms

Answer Key: D

Question 2 of 12 2.0 Points

Microbiologists investigate problems by designing and carrying out experiments. What is true about the scientific method? A.a hypothesis is the definitive explanation to account for the observation and therefore does not need to be tested B.a prediction is the factor that can change but is prevented from changing during the duration of the experiment
Correct C.a good hypothesis is one that offers the simplest most reasonable explanation and can be tested. D.the goal of an experiment is to prove that scientists are always correct in their predictions

Answer Key: C

Question 3 of 12 2.0 Points

Microbiology continues to be an important research field for all of the following reasons, except:
Correct A.all infectious diseases have had vaccines developed and therefore can be prevented B.many forms of genetic engineering depends on microorganisms C.new and emerging diseases like AIDS and SARS D.microorganisms can be used as factories to cheaply produce drugs, hormones and vaccines

Answer Key: A

Question 4 of 12 2.0 Points

Electron microscopes A.that are scanning have better resolution than those that are transmission
Correct B.are much more expensive and take up more space than light microscopes C.can use the same preparations of specimens that have been prepared for viewing with a light microscope D.have a resolving power approximately 10 times better than the best light microscope

Answer Key: B

Question 5 of 12 2.0 Points

Transmission electron microscopes have a maximum magnification of A.1,000X B.100,000X
Correct C.500,000X D.1,000,000X

Answer Key: C

Question 6 of 12 2.0 Points

Which stain would be the best choice for detecting mycobacterium (the bacteria responsible for tuberculosis and leprosy)? A.simple stain B.endospore stain
Correct C.acid-fast stain D.Gram stain

Answer Key: C

Question 7 of 12 2.0 Points

Which type of staining results in a clear object being viewed against a dark background? A.simple stain
Correct B.negative stain C.endospore stain D.flagellar stain

Answer Key: B

Question 8 of 12 2.0 Points

A simple stain
Correct A.uses only a single dye B.requires only one step to stain a slide C.distinguishes between two different parts of an organism D.is composed of an equal balance of acid and basic dyes

Answer Key: A

Question 9 of 12 2.0 Points

Which of the following statements about preparing a specimen is false?
Correct A.organisms must be heat fixed before viewed in a hanging drop slide B.smears are loopful of medium spread on the surface of a glass slide C.wet mount preparations give good views of microbial mobility D.the depth of a smear affects the results as too thin you may find no organisms

Answer Key: A

Question 10 of 12 2.0 Points

Three dimensional views of cells and other small objects could best be obtained using a A.phase contrast microscope B.dark-field microscope
Incorrect C.transmission electron microscope D.scanning electron microscope

Answer Key: D

Part 2 of 2 - Part II 10.0 Points

Question 11 of 12 5.0 Points

What is the germ theory of disease? What did people believe caused disease to be transmitted before the germ theory of disease? Describe one experiment that supported the germ theory. Name an important innovation that arose from the germ theory of disease.The Germ theory states that actions of specific micro-organisms within the body cause many diseases. Prior to the Germ theory, many people believed that a disease was a punishment for a person's evil behavior or their sin’s. One experiment that supported the germ theory was bottles of sour wine being contaminated with microbes. Pasteur observed wine that had soured and compared it to wine that had not. He found that all soured wines contained larger numbers of cells. Yeast cells are required for fermentation of wine, so even great wine has yeast cells. Sour wine, however, was full of many smaller cells that were not yeast. Pasteur determined that the microbes, which had contaminated the wine, were the cause of the poor quality. The use of aseptic surgical techniques and sanitation in medical settings was a development that came from the Germ theory. The germ theory paved the way for better medical treatment.

Model Short Answer: The germ theory of disease posits that microbes invade other organisms and are the agents of disease.

The belief was that microbes originated from non-living things. This concept was known as spontaneous generation.

One experiment that supported the germ theory was by Franseco Redi who placed gauze over meat demonstrating that no flies could come out of the covered meat no matter how rotten it was.

A critically important innovation that resulted from the germ theory of disease was Robert Koch's method of staining and identifying the bacterium that caused tuberculosis.

Question 12 of 12 5.0 Points

Describe the gram stain. What does it distinguish?The Gram stain is a staining technique that is used to classify bacteria. The Gram stain is used to differentiate two large groups of bacteria based on their different cell wall constituents. The Gram stain distinguishes between Gram negative and Gram positive groups by coloring these cells violet or red. Gram positive bacteria will stain violet because of the presence of a thick layer of peptidoglycan in their cell walls. This layer will retain the crystal violet that the cells were stained with. On the other hand, Gram negative bacteria will stain red. This is because their cell wall is thinner and does not retain the crystal violet.

Model Short Answer: The Gram stain was invented by Christian Gramm. It is a commonly used differential stain where bacterial cells take up crystal violet then iodine is added to help certain cells retain the stain. Those cells that cannot retain violet are decolorized with 95% ethanol or ethanol-acetone solution, rinsed and counterstained with safranin.

The Gram stain distinguishes between four different groups of organisms which are: Gram-positive, gram-negative, gram-non reactive, and gram-variable organisms.