Discussion Questions Unit 1

Question 1

“I was able to track down the source of the cholera epidemic in London.” Who am I?

Answer 1

John Snow

Question 2

“Everyone thought that I was crazy to think that an abnormal protein could cause a neurological disease.” Who am I?

Answer 2

Stanley Prusiner

Question 3

“I was able to disprove the theory of spontaneous generation just by using a Swan-neck flask.” Who am I?

Answer 3

Louis Pasteur

Question 4

Eukaryotic cells are almost always larger than prokaryotic cells. What structures might allow for their larger size?

Answer 4

Membrane bound organelles: RER, Golgi, mitochondria, chloroplast

Question 5

Methylene blue binds to DNA. What parts of a yeast cell (fungus) would be stained by this dye? (Hint: where do you find DNA in a eukaryote? & Which organelles have DNA)

Answer 5

Nucleus & Mitochondria

Question 6

Colchicine is a drug that inhibits microtubule formation. Why does colchicine inhibit phagocytosis, movement of organelles within the cell, and formation of flagella and cilia? (What is cytoskeleton made of?)

Answer 6

No microtubules means that cells can’t build flagella and cilia which means no movemment

Question 7

The smallest single-celled, free-living eukaryote known is a green photosynthetic alga, Ostreococcus tauris. What membranous organelles must this photosynthetic cell have?

Answer 7

Chloroplasts; Since its photosynthetic

Question 8

Even though Clostridium is strictly an anaerobic bacterium, it can be isolated easily from the exposed surface of your skin. Explain how this can be. (Protective structure)

Answer 8

Endospores

Question 9

Some bacterial toxins cause cells lining the digestive tract to secrete ions, making the contents of the tract hypertonic. What effect does this have on a patient’s water balance?

Answer 9

Dehydrations because the water will go towards the tract (diarrhea)

Question 10

Following the bioterrorist anthrax attacks in the fall of 2001, a news commentator suggested that people steam their mail for 30 seconds before opening it. Would the technique protect people from anthrax infections? Why or why not?

Answer 10

No, because 30 seconds of steam is not enough to kill any bacteria

Question 11

After a man infected with the bacterium Escherichia coli was treated with the correct antibiotic for this pathogen, the bacterium was no longer found in the man’s blood, but his symptoms of fever and inflammation worsened. What caused the man’s response to the treatment? Why was his condition worsened by the treatment? (CW, Gram+ or Gram-?)

Answer 11

Gram Negative CW contains an endotoxin called Lipid A, The antibiotic most likely attacked the CW that released Lipid A causing the patients symptoms to worsen

Question 12

I have two parts that must work together for me to function. I have two forms in eukaryotes but one in prokaryotes. If I stop working, then enzymes won’t be made. What cellular structure am I?

Answer 12

Ribosomes

Question 13

Where are ribosomes found? In Eukaryotes and Prokaryotes

Answer 13

Eukaryotes: found both free in the cytoplasm and attached to the endoplasmic reticulum,

Prokaryotes: only free in the cytoplasm

Question 14

As protozoa if I don’t have this cellular structure then I most likely can’t perform aerobic respiration. What organelle am I?

Answer 14

Mitochondrion; because they produce energy

ATP

Question 15

E. coli can perform aerobic respiration but doesn’t have the organelle found in animal cells. So, what structure allows bacteria to siphon electrons from NADH using oxygen as the final electron acceptor to make ATP?

Answer 15

Cell membrane; in E. coli it contains the electron transport chain

Question 16

I protect against osmotic stress in both plants and bacteria. What cellular structure am I?

Answer 16

Cell wall

Question 17

In 1985, an Israeli scientist discovered the single-celled microbe Epulopiscium fishelosoni. This organism is visible with the naked eye. Why did scientists initially think Epulopsicium was eukaryotic? What discovery revealed that the microbe is really a giant bacterium?

Answer 17

Because of its size;

Evidence:
No nucleus (microscopy image)
rRNA information (genetic)

Question 18

Microbiologists announced the discovery of over 30 new species of bacteria that thrive between the teeth and gums of humans. The bacteria could not be grown in the researchers’ laboratories, nor were any of them ever observed via any kind of microscopy. If they couldn’t culture them or see them, how could the researchers know they had discovered new species? If they couldn’t examine the cells for the presence of a nucleus, how did they determine that the organisms were prokaryotes and not eukaryotes?

Answer 18

rRNA

They most likely looked at the genetic information since they had no microscopy evidence

Question 19

A scientist who discovers a prokaryote living in a hot spring at 100°C suspects that it belongs to the archaea. Why does she think it might be archaeal? How could she prove that it is not bacterial?

Answer 19

Most hyperthermophiles are archaea;

she can prove it is not bacterial through rRNA

Question 20

Joe Micro observed his TSA plate to determine whether he used proper aseptic technique. On his plate, he noticed two different types of colonies of bacteria yellow, shiny, opaque, small colonies growing along the edges of the plate & beige, dry, crusty growth in a single line in the middle of the plate. After looking at his lab notebook, he noted that the culture he used was beige, dry-looking growth & that he made a single streak line in the middle of the plate. What is one possible explanation for this observation?

Answer 20

Cross contamination

There might have been accidental contamination to create the different colonies

Question 21

If you were to gram stain Mycoplasma sp., then what color would these cells be? Why?

Answer 21

They would be colorless (or pink) because mycoplasma lacks a cell wall (but the dye can still stain)

Question 22

If you were to gram stain Archaeal cells, then what color would the cells be? Why?

Answer 22

They would likely appear pink (or Gram-negative) because most archaea lack peptidoglycan in their cell walls, a key component that retains the crystal violet stain in Gram-positive bacteria.

Question 23

Jo Micro gram stained a bacterial sample that she was told was a 24-hour culture of a Gram negative rod-shaped bacteria. When Jo looked at her stained smear under the microscope, all she saw were purple monobacillus. What could have been the problem?

Answer 23

Under-decolorization; the alcohol may not have been applied long enough, causing the Gram-negative bacteria to retain the crystal violet dye, making them appear purple

Question 24

Miki came home from microbiology lab with green fingers and a bad grade. When asked about this, she replied that she was doing a Gram stain but that it never worked the way the book said it should. Christina overheard the conversation and said that she must have used the wrong chemicals. What dye was Miki probably using, and what structure does that chemical normally stain?

Answer 24

Miki was likely using malachite green;

Malachite green is used to stain endospores

Question 25

Pasteur had cultured a sample of Clostridium botulinum in the 1860’s. A French microbiologist just found a tube of what looked like a bacterial culture in the home of Louis Pasteur. He took a sample and did two things: (1) made a new culture and (2) looked at the original culture under microscopy. The culture grew without issue after centuries. The microscopic smear had cells with what structure inside of them that allowed them to survive centuries? What staining procedure did this microbiologist do to determine the reason the new culture was able to grow after centuries?

Answer 25

The structure inside the cells that allowed them to survive for centuries was endospores;

The microbiologist likely performed an endospore stain to identify these structures.

Question 26

You are a Medical Lab technologist. You are given a sputum sample from Patient ER56 suspected of having tuberculosis (TB). You make a smear. What stain would you do in order to determine whether this patient’s sample could possibly have the TB bacteria?

Answer 26

Acid-fast stain

Question 27

Problem with staining procedure: Hypothesize what the problem with the staining procedure might have been based upon what you know about the staining procedure.
a) Acid fast staining: All cells of a mixed bacterial culture were blue. (note: only one was acid-fast.)

Answer 27

a) Acid-fast staining: The issue likely arose during the carbol fuchsin staining step or the decolorization step.

If the carbol fuchsin stain was not properly applied or not given enough time to penetrate the acid-fast cell wall none would be red

or if over-decolorization occurred, even acid-fast bacteria would lose their stain and appear blue after the methylene blue counterstain.

Question 28

Problem with staining procedure: Hypothesize what the problem with the staining procedure might have been based upon what you know about the staining procedure.

b) Endospore staining: Pink rods with clear oval inside. (note: broth sample was 72 hours old that should be enough time to sporulate.)

Answer 28

b) Endospore staining: The clear ovals suggest that the endospores did not take up the stain.

This could have happened if the malachite green stain was not heated enough to penetrate the tough spore coat, or if the staining process was not carried out long enough.

As a result, the spore remained unstained (clear), while the vegetative cells appeared pink due to the safranin counterstain.

Question 29

What are NAM and NAG?

Answer 29

NAM and NAG are monosaccharides (sugars) that make up the cell wall of bacteria

Question 30

What is NAM and what does it do?

Answer 30

N-acetylmuramic acid (NAM) is a component of the peptidoglycan layer in bacterial cell walls. It provides structural support and stability by forming cross-links with peptide chains, which helps maintain the integrity of the cell wall.

Question 31

What is NAG and what does it do?

Answer 31

N-acetylglucosamine (NAG) is another key component of the peptidoglycan structure, and it alternates with NAM in the polymer chain.

NAG contributes to the overall strength of the cell wall and is essential for the formation of the glycan strands that provide rigidity and shape to the bacterial cell.