Download Quiz 3 slides - Minot State University

-Woese, Micro. Rev.,
1987
Figure 04.05
Figure 04.07b
Part I - Mysterious Illness
• Well, Becky thought, being a dorm counselor for
freshmen was not going to be that bad. She got a free
room for the year and the food was plentiful - free
steaks last week at an outdoor BBQ followed by a hay
ride in a horse-drawn wagon in their welcome
celebration.
• But, then again, it wasn’t perfect: she had ended up
covered in bug bites; some of the students got sick
from eating steak that was burned on the outside and
raw in the middle; the horses had mucked up the
courtyard; and pigeons had roosted on the dorm roof.
• At least tonight the students were finally settling in and
quieting down, she mused.
1
Part I, continued…
• The quiet was shattered a few minutes later when one
of the other counselors, Ann, yelled through her door:
• “Becky, we’ve got a problem. One of the students
found a homeless kitten, and the girl has been
keeping her in her room. I only found out because the
girl, Ellie, just came to my room complaining of being
sick. I felt sick too when I saw the mess that kitten
made. I thought cats were born housebroken, but I
guess not.”
• “Anyway, now I think Ellie might really be sick,” Ann
continued. “She’s feverish and says she’s going to
throw up.”
2
Part I, continued
• “What do you want me to do?” Becky asked.
• “I’m freaking out!” Ann answered. “Forget about the
mess, just help me figure out what to tell them at the
health center. I don’t know what she’s been exposed
to. Or what we’ve been exposed to for that matter! This
is the second girl this week with aches, fever, and
nausea.”
• “My Mom sent me a bunch of medicine,” Becky
answered. “I’ll make a list of where we’ve been, what
we’ve eaten, and what we’ve possibly been exposed
to. Then we can start taking something right away to
keep from getting it, too.”
3
Becky’s Task
•
The Health Center will be using the
differences between organisms to
diagnose and treat Ellie.
•
In the next 2 minutes, list the clues in the
story that help you identify how Ellie could
have contracted a disease with flu-like
symptoms.
4
Your Task
•
Becky did an Internet search and found 5 possible
suspects that could be causing Ellie’s illness.
•
During this class session we will investigate the
differences between them.
•
Organisms are usually distinguished by the
characteristics you listed in your homework answers
to Table 1. Add any details you missed so that
when you hear the results of the Health Center
tests you will be able to figure out what was making
Ellie sick.
•
Fill in possible drug treatments in Table 2.
5
Ellie’s Diagnosis
• Initial Identification: The Health Center collected
blood samples from Ellie and observed her cells
under a microscope. They identified foreign
structures with DNA and outer membranes. The cells
were gram negative and about 1/10 the size of her
cells.
• “Ah, ha!” said Becky. “That matches one of my
suspects. I knew those were a health hazard. I just
need to re-check the size thing. This internet chart
compares our cells to viruses and stuff.”
6
Metric Review
10-3
1 mm
Cells like
ours
10-4
10-5
meters
• 1 meter (m) = ~3 feet
• 1 meter (m) = 1000
millimeter (mm)
• 1 millimeter (mm) = 1000
micrometer (µm) (smallest
size distinguished by naked
eye)
• 1 micrometer (µm) = 1000
nanometer (nm) (only seen
with light microscope)
• 1 mm poppy seed = (1000
µm/mm) = 1000 µm
10-6
Bacteria
1 µm
10-7
Viruses
10-8
Proteins
10-9
1 nm
Atoms
7
Becky’s Internet Search
Results – List of Suspects
Suspect 1: Coxiella
burnetii causes Q-fever.
Coxiella are often found in
livestock and are excreted in
milk, urine, and feces. Infection
occurs 2-3 weeks after inhalation
of barnyard dust. They are 0.30.5 µm gram-negative bacterium
(prokaryotes) that must invade
and reside inside human cells to
cause infection.
1µm
8
Prokaryotes
•
•
•
Unicellular
Reproduce asexually
Composition
– Protected interior (cytoplasm) that contains genetic material (one
circle of DNA) as well as complexes of protein enzymes to carry
out necessary functions of gathering energy, manufacturing
proteins (ribosomes), etc.
9
Prokaryotes
• Size
– 0.2-10 micrometer (µm)
• Composition
– Phospholipid membrane, many contain
cell wall composed of peptidoglycan
(positive for chemical Gram stain), those
with little or no peptidoglycan called Gram
negative (like Coxiella).
10
CQ1: “That’s great,” Becky said. “My Mom sent
me 3 different antibiotics to kill bacteria.”
Given the description of Ellie’s test results,
which antibiotic will definitely NOT work:
Penicillins blocks the enzyme
that normally creates
bacterial cell walls.
Streptomycin blocks bacterial
ribosomes.
Ciprofloxacin blocks a bacterial
DNA replication enzyme
CQ2: “Wait a minute!” Ann said. “The doctor
said the blobs in Ellie’s blood were 1/10th the
size of her cells. Could they be Coxiella?”
10-3
1 mm
Cells like
ours
10-4
meters
10-5
10-6
Bacteria
1 µm
10-7
Viruses
10-8
Proteins
10-9
1 nm
Atoms
Part II: Microscope Analysis
Becky and Ann talked together outside the student’s room at the
student health center the next morning.
“You’re right!” Becky exclaimed after viewing photographs of
Ellie’s blood up close. “I wish I hadn’t started taking the
antibiotics. The little crescent shaped structures that I thought
were the bacteria may not be. They aren’t too big to be
bacteria, but they aren’t too small to be mitochondria or some
kind of protozoan parasite.”
“Wait a minute,” Ann replied. “The things on the right are the
pathogens? Look at their insides, they can’t be bacteria.”
“Why not?” Becky asked.
13
Part II, Continued
“Wait a minute,” Ann replied.
“The things on the right are
the pathogens? Look at their
insides, they can’t be
bacteria.”
“Why not?” Becky asked.
1µm
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CQ3: “Well,” Becky admitted, “there should be differences between Ellie’s
cells and the little blobs they saw. Otherwise, it might mean one of my
other suspects is the cause. These are some of the structures normally
found in all cells.”
“No,” Ann answered, “one isn’t.”
Which structure is NOT found in all cells?
Becky’s Internet Search
Results – List of Suspects
Eukaryote - Suspect 2:
Cryptococcus neoformans
2.5-10 µm encapsulated fungus found
in decaying pigeon or chicken
droppings. Inhaled as spores that
eventually spread to the brain causing
meningoencephalitis. Has a black
pigmented layer that can be seen
sometimes on bird seed.
17
Becky’s Internet Search
Results – List of Suspects
Eukaryote - Suspect 3:
Toxoplasma gondii
• 4-6 µm single-celled
protozoan parasite of mammals
& birds.
• Most likely acquired through
ingesting cysts in undercooked
meat.
Toxoplasma gondii cyst
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Toxoplasma movie
2
9
Becky’s Internet Search
Results – List of Suspects
Suspect 3:
Toxoplasma gondii
• Usually no symptoms, but can cause
flu-like complaints.
• Sexual life cycle occurs in cats, so
infection can follow contact with cat
feces.
19
Eukaryotes
• Uni- or multicellular.
• Reproduce asexually &
sexually.
• Composition:
– Genetic material (long linear strands of
DNA chromosomes) enclosed in a double
membrane (nucleus)
– Some have cell walls (plants have
cellulose, fungi ß-glucan)
20
Eukaryotes
• Size 10-100 (µm)
• Composition:
– CM and internal membranes are a
phospholipid bilayer outside.
– Internal membranes separate
functions such as gathering and
transforming cellular energy and
manufacturing macromolecules.
21
Eukaryotic Organelles
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Becky’s Anti-Eukaryotic Medicines:
•Pyrimethamine, Sulfonamides: Interfere with enzymes used to
make the folic acid needed to make thymine and uracil
nucleotides.
•Polyenes combine with a component of fungal and some
bacterial membranes, disrupt and break them.
One of these drugs specifically affects one of the two eukaryoti
suspects. Which test of Ellie’s blood would help you tell which
eukaryotic suspect she was infected with?
A: Presence of DNA.
B: Presence of ß-glucan-containing cell walls.
C: Presence of cellulose.
D: Presence of peptidoglycan cell walls.
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One of these drugs specifically affects one of the two
eukaryotic suspects. Which test of Ellie’s blood would
help you tell which eukaryotic suspect she was infected
with?
Part III: Viruses
• Becky and Ann are back at the dorm waiting for the
results of more tests.
• “I’ve also got some tamiflu,” Becky volunteered. “I
mean, what if those cells in the picture aren’t really
making her sick. Maybe she just has the plain old
flu.”
• “What do you mean?” Ann asked. What’s the
difference?”
• “Flu is a virus,” Becky answers. “I’ve actually got
two suspects that are viruses. They’re probably
the most different from the prokaryotes and
eukaryotes. They’re not even cells.”
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Becky’s Internet Search
Results – List of Suspects
Electron micrographs
4. Influenza Virus: Spread primarily
through respiratory droplets from
sneezing or coughing. Virus has
single strand of RNA surrounded by
phospholipids/protein envelope (80120nm).
5. West Nile Virus: Spread by
mosquitoes that have previously fed
on infected birds. 20% of infected
people show symptoms. Single
stranded RNA, phospholipid/protein
envelope (50nm).
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Viruses
• Not cells
• Cannot reproduce alone
– hijacks a host cell to replicate itself.
• Composition
– Outer shell: repetitive protein often inserted
into a lipid envelope (responsible for
recognition and infection of host cell.)
27
Viruses
• Size
– 100 times smaller than bacteria
• Composition
– Protected interior that contains genetic
material (DNA or RNA) with important
protein enzymes required for duplication.
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virus replication
4
0
Table 1
Take a few minutes to complete the homework table comparing
viruses, bacteria, and eukaryotes.
31
Part IV: DNA Analysis
“Well, it isn’t viral,” Becky said, closing her cell
phone. “No neuraminidase. But, they found some
foreign DNA with the sequence: AACGTGGTCGTT.
The closest match is a gene used to make
ribosomes (rDNA). They are searching a huge DNA
database of sequences to find the organism that
has the closest match.”
33
CQ6: Foreign DNA sequence isolated from Ellie:
ACGTGGTCGTT.
Which sequence is the best match with this
foreign DNA?
A: Ellie’s nucleus
ATGGTCTCAATG
B: Ellie’s mitochondria
TTGGTCCGTCAG
C: Coxiella bacteria
TTGGTCGGTCAG
D: Toxoplasma nucleus
AACGTGGTAGTT
E: Cryptococcus nucleus
ATGGTGGCAATG
Strange Similarities
“What’s weird is that Ellie’s mitochondrial DNA
matches the Coxiella sequence so closely.”
Ellie’s mitochondria TTGGTCCGTCAG
Coxiella bacteria
TTGGTCGGTCAG
“That makes sense in a way,” Ann answered.
“There is a lot of evidence that points to
mitochondria being descendents of gram-negative
bacteria just like Coxiella.”
“What type of evidence?” Becky asked.
35
Eukaryotic Organelles & Endosymbiosis
prokaryote
N
C
N
Strange similarities:
1. Chloroplasts and mitochondria are the same
size as prokaryotes.
2. Both have circular DNA without histones with
similar sequence to photosynthetic bacteria
(cyanobacteria) and obligate intracellular
rickettsia bacteria.
3. Both divide like prokaryotes.
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Eukaryotic Organelles & Endosymbiosis
prokaryote
N
C
N
Strange similarities:
4. Have their own protein synthesis machinery
(ribosomes) more like bacteria than eukaryotes
(sensitivity to Streptomycin).
5. Inner membrane of mitochondria contains
unusual phospholipid characteristic of bacterial
membranes.
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Finale: Ellie’s Prognosis
“Well, Ellie’s responding well to the pyrimethamines that the
doctors prescribed,” Becky commented to Ann while checking
her email a few days later at the dorm.
“Yeah, and we’re lucky the cipro we took couldn’t harm our
cells,” Ann replied. “We were so wrong! I’m never selfmedicating again. Do you think we should warn the other
students. They might have had contact with the kitten, too.”
“We don’t know if it was from cat poop,” Becky answered. “I
learned that something like 25-40% of American adults are
already infected with Toxoplasma gondii, and not because of their
cats—usually it’s from eating raw meat. Plus, apparently the
oocysts in fresh cat poop aren’t infectious for a couple of days.
So, if you scoop the box right away you don’t have to worry.”
“So now I have to know how often the cat box is cleaned?! I
don’t think I’m cut out for this job!” Ann moaned.
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“Take Two and Call Me in the
Morning”
A Case Study in Cell Structure and Function
by
Peggy Brickman
University of Georgia