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BioSc221/325
Exam 1
Name ______________________________
Multiple choice. (1 point each) Choose the one best answer to each of the following questions.
____ Based on evidence from fossilized stromatolites, the earliest microorganisms came into existence at least
A.
B.
C.
D.
6000 years ago
3 million years ago
60 million years ago
3.5 billion years ago
____ Thiomargarita namibiensis (sulfur jewel of Namibia) holds the current worlds record as the largest prokaryotic organism
(some cells are greater than one millimeter in diameter). Why are prokaryotic organisms of this size unusual?
A.
B.
C.
D.
The low surface of volume ratio of such large cells creates problems for intracellular transport processes.
The membranes of such large cells become very unstable.
Synthesis of the peptidoglycan polymer for making the cell wall becomes limiting.
The organelles of such large cells become too large.
____ Escherichia coli strain O157:H7 is a dangerous strain that can cause severe illness, particularly in young children,
immunocompromised adults and the elderly. The O157 part of the strain designation refers to
A.
B.
C.
D.
the location where the strain was isolated
the number of the gene that produces the bacterial toxin which causes the severe symptoms
a specific polysaccharide component of the lipopolysaccharide found on the surface of the bacterium
the first outbreak was associated with a contaminated bottle of Heinz 57 steak sauce used at Jack-in-in-the-Box.
____ The diamino acid containing pentapeptide involved in cross-linking adjacent peptidoglycan polymers is associated with
which component of the peptidoglycan chain
A.
B.
C.
D.
NAM
NAG
N-acetyl --Lysine
bactoprenol
____ The enzyme lysozyme which is found in human tears helps protect the eyes from bacterial infection. Lysozyme damages
bacteria by
A.
B.
C.
D.
penetrating the cytoplasmic membrane and lysing the cell from within
degrading porin proteins in the outer membrane and preventing nutrient uptake
cleaving the -1,4 linkage of the peptidoglycan polymer
degrading lipoteichoic acid
____ Which of the following would be found in the cell wall of Gram-negative but not Gram-positive bacteria?
A.
B.
C.
D.
lipopolysaccharide
teichuronic acid
teichoic acid
fimbrae
____ Which of the following distinguishes prokaryotic flagella from eukaryotic flagella?
A.
B.
C.
D.
Prokaryotic flagella are make entirely of protein
Prokaryotic flagella are not surrounded by a cell membrane
Prokaryotic flagella rotate like a motor
All of the above distinguish prokaryotic flagella from eukaryotic flagella
____ Approximately 2 billion years ago, a dramatic increase in biodiversity is observed in fossilized stromatolites. This
coincides with what significant event?
A.
B.
C.
D.
E.
The sudden appearance of eukaryotic organisms.
The sudden appearance of photosynthetic organisms.
An significant increase in molecular oxygen in the atmosphere.
The sudden appearance of animals
The sudden appearance of plants.
____ Where is lipopolysaccharide found?
A.
B.
C.
D.
In the cytoplasmic membrane
In the periplasm
In porins
In the outer membrane
____ What is a protoplast?
A.
B.
C.
D.
A bacterial cell that has lost its peptidoglycan layer causing it to round up and become osmotically sensitive
An intracellular structure containing chloroplasts
A round bacterial cell
The first bacterial cell
____ Which of the following is NOT an intracellular feature of bacteria?
A.
B.
C.
D.
gas vacuoles
poly--hydroxybutyric acid (PHB)
metachromatic granules
fimbrae
____ Curved bacteria that are shaped like a simple "bent rod" are called
A.
B.
C.
D.
spirilla
spirochaetes
vibrios
commas
____ The Winogradsky column is
A.
B.
C.
D.
an enrichment culture
named for a microbiologist
a way to see growth and succession of anaerobes
all of the above
____ An organism that uses light as its energy source and carbon dioxide as its carbon source is called a
A.
B.
C.
D.
Photoautotroph
Photoheterotroph
Chemoautotroph
Chemoheterotroph
____ Sergei Winogradsky discovered chemoautotrophic organisms by setting up enrichment cultures containing
A.
B.
C.
D.
Only H2S as an energy source and only CO2 as a carbon source
Only glucose as an energy source as well as a carbon source
Only H2S as an energy source and only glucose as a carbon source
Only light as an energy source and only glucose as a carbon source
____ MacConkey medium is a common medium used in the clinical microbiology laboratory. MacConkey medium contains
peptone, lactose and a pH indicator so that lactose fermenting organisms turn red and oxygal, a compound that inhibits the
growth of Gram-positive bacteria. MacConkey would best be described as a ___ medium.
A.
B.
C.
D.
defined
differential
selective
both selective and differential
____ Which of the following is not a technique for isolating a pure culture of a specific bacterium?
A.
B.
C.
D.
Streak plate
Dilution
Enrichment
All of the above techniques are used for isolating bacteria
____ Which of the following is the most accurate method for counting bacteria?
A.
B.
C.
D.
Direct count
Viable count
Turbidity
Cell mass measurement
____ A chemostat is used for
A.
B.
C.
D.
large scale batch culturing of bacteria for commercial use
enriching for chemoheterotrophs
continuously counting bacteria
continuous culturing of bacteria under constant, defined conditions
____ Which of the figures below shows the behavior of bacteria [viable count (solid line) and total count (dashed line] after
addition of a bacteriostatic agent?
A.
B.
C.
D.
Figure A
Figure B
Figure C
None of the Above.
____ Catalase activity is a classic diagnostic tool for certain groups of bacteria. The function of catalase in a bacterial cell is
A.
B.
C.
D.
to detoxify the toxic oxygen species - hydrogen peroxide
to protect the cell from osmotic stress
to protect the cell from elevated pH
to cause cat-scratch disease
____ Halophilic bacteria protect themselves from potentially dangerous osmotic imbalance by either producing or acquiring
A.
B.
C.
D.
a thick cell wall
a high G+C content in their DNA
new phospholipids
compatible solutes
____ Listeria monocytogenes grows optimally at 30 degrees centigrade but also grows at 4 degrees centigrade, it would be best
described as
A.
B.
C.
D.
Psychrophilic
Mesophilic
Thermophilic
Hyperthermophilic
____ Which of the following is not a strategy used by bacteria to tolerate elevated growth temperatures?
A.
B.
C.
D.
Changing the lipid composition of their cytoplasmic membrane
Producing and acquiring compatible solutes
Having DNA composed of a high G+C content
Modifying critical enzymes to be more stable at higher temperatures
____ What is a decimal reduction time?
A.
B.
C.
D.
The time it takes to reduce the viable population of bacteria 90%
The time it takes to reduce the viable population of bacteria 10%
The time it takes to kill viable spores
The time it takes to kill viable vegetative cells
____ Which of the following is not an effective method of sterilization?
A.
B.
C.
D.
E.
High temperature and pressure
Gamma radiation
Ethylene oxide gas treatment
Filter sterilization
All of the above are effective methods of sterilization
____ Minimal inhibitory concentration (MIC) is defined as
A.
B.
C.
D.
The size of the zone of inhibition surrounding a filter disk containing an antimicrobial compound
The concentration of an antimicrobial compound that produces a zone of inhibition of 2 centimeters
The effective dose of a chemotherapeutic agent
The lowest concentration of an antimicrobial compound that completely inhibits growth
Matching. (1 point each) Match the historical figure in the left column with the appropriate discovery they are associated with
in the right column. Note, not all terms in the column on the right will be used.
____ Edward Jenner
A. Discovered “animalcules”
____ Sergei Winogradsky
B. Identified the cause of childbed fever
____ Ignaz Semmelweis
C. Solved an outbreak of Cholera in London
____ John Snow
D. Discovered spores
____ Antoni van Leeuwenhoek
E. Created the first vaccine, using cowpox to prevent smallpox
____ John Tyndall
F.
Discovered autotrophy
G. Discovered Salvarsan, the first chemotherapeutic agent
Short answer. (1 point each)
Describe the following shapes or arrangements of bacteria using the appropriate terminology.
_____________________
________________________
_________________________
You are observing a new bacterial isolate in a wet mount with your phase-contrast microscope. You notice that the bacteria
swim about somewhat randomly but the vast majority of the bacteria seem to be congregating at the outer edges of the
coverslip. What do you think is happening?
What is the purpose of the Safranin (red) dye in the gram stain procedure?
When nutrient concentrations are low, many bacteria will attach to surfaces. A classic example of this is Caulobacter
crescentus which attaches to surfaces via a “stalk”. Briefly explain an advantage a bacterium derives from attaching to a
surface.
What are Koch’s postulates? (i.e. name them)
What are the 3 main structural parts of a bacterial flagellum?
What is the difference between a selection strategy for isolating a specific type of organism and a screening strategy?
Short Essay Questions. Please answer 3 of the following 4 short essay questions (5 points each - 5 bonus points possible for
answering all 4 questions)
Draw a bacterial growth curve that plots optical density (Absorbance at 600 nm) versus time over a period of several days.
Assume that a bacterial culture was allowed to grow to saturation and for several days and then inoculated into fresh medium.
Be sure to label the axis, indicate the phases of the growth curve and explain what is happening during each phase.
What are stromatolites? How are they formed and what do fossilized stromatolites tell us about the origins of life on Earth.
Describe how thioglycolate medium is used to determine the relationship of an organism to oxygen. Explain the function of
the various key ingredients of the thioglycolate medium. Describe the growth pattern you would expect to observe for a strict
aerobe, strict anaerobe, facultative and microaerophilic organism (a labeled drawing would be sufficient).
Describe the key features and advantages/disadvantages of brightfield, phase contrast, dark field and electron microscopy.