Cell Structure
Which of the following "clinically relevant" microbes are classified as prokaryotic?
a) Fungi b) Viruses c) Bacteria d) Protozoa
c) Bacteria
After a Gram stain, what color do Gram-negative bacteria appear?
Pink or red
What is the general purpose of adhesion structures for bacteria?
To stick to surfaces and cells, which is often important for causing disease.
In which two forms do most fungi spend their lives?
Mold and yeast forms.
Which protozoan genus causes malaria?
Plasmodium
What are the three major types of helminths?
Trematodes (flukes), Cestodes (tapeworms), and Nematodes (roundworms).
All cells, both prokaryotic and eukaryotic, share which four common structures?
Plasma membrane, cytoplasm, ribosomes, chromosome(s)
What is the primary material that makes up the thick layer of a Gram-positive cell wall?
Peptidoglycan
What is an endospore, and what does it mean to say endospores are dormant?
An endospore is the cell's chromosome wrapped in protective protein layers; dormant means it is metabolically inactive and does not undergo cell division.
What is the generic name for the visible "body" of a mold?
Mycelium.
How do humans typically become exposed to Giardia infection?
By consuming Giardia cysts in contaminated food or water, often from unsanitized natural sources.
What are the intermediate hosts for beef tapeworm and pork tapeworm?
Cows for beef tapeworm, and pigs for pork tapeworm.
What is a key difference between prokaryotic and eukaryotic ribosomes?
Eukaryotic ribosomes (80S) are larger and have a more complex structure than prokaryotic ribosomes (70S).
What component of Gram-negative bacteria, also known as endotoxin, can make infections especially dangerous by causing high fever and organ stress?
Lipopolysaccharide (LPS), specifically Lipid A
What are two significant benefits of biofilms for bacteria that make them a problem in medical microbiology?
They provide adhesion and layers of protection, making bacteria resistant to antibiotics and the immune system.
What is one important way fungal spores are different from bacterial endospores in terms of resistance?
Fungal spores are not nearly as tough/resistant as bacterial endospores.
What is a "latent infection" and how does Toxoplasma cause it in humans?
A dormant infection inside the human body, where Toxoplasma forms dormant tissue cysts after a brief infection, which can remain for decades.
What are the three major anatomical parts of an adult tapeworm?
Scolex (has suckers and hooks to attach the worm to the intestine wall), Neck (site of growth of the worm’s proglottids), and Proglottids (long chain of reproductive structures).
A new antibiotic is being developed that specifically targets and binds to 70S ribosomes, blocking protein synthesis. Why would this antibiotic be effective against bacterial infections but generally safe for human cells and eukaryotic microbes like fungi?
Because human cells and eukaryotic microbes have 80S ribosomes, which have subtle structural differences preventing the antibiotic from binding, while bacterial cells have 70S ribosomes that are targeted.
A Gram stain is performed on a patient's throat swab, revealing numerous purple, spherical cells arranged in chains. What is the likely Gram stain result (Gram + or Gram -) and cellular arrangement, and if the infection is confirmed to be bacterial, why might penicillin be an effective first-line treatment?
Gram-positive, streptococci; penicillin would be effective because it targets the thick peptidoglycan layer characteristic of Gram-positive bacteria.
Bacteria that cause urinary tract infections often use fimbriae to adhere to host cells. Why are adhesion structures like fimbriae particularly critical for bacteria to cause disease in environments with fluid flow, such as the urinary tract?
Without adhesion structures, bacteria would be easily washed away by the continuous flow of urine, preventing them from establishing an infection.
Where are Candida yeasts normally found in the body, and why are they considered opportunistic pathogens?
Candida can be found in the "healthy microbes" (normal microbiota) of the skin, mouth, intestinal, urinary, and vaginal tracts; they are opportunistic pathogens because if the normal physiological balance in these places is thrown off, Candida will overgrow and cause infections.
What are the characteristic cyclical symptoms of uncomplicated malaria, and why do they occur in a 12-72 hour cycle?
Flu-like symptoms with cyclical fever, chills (full body shaking), and profuse sweating, occurring every 12-72 hours, corresponding with the death of red blood cells in each cycle of parasite replication in the red blood cell stage.
Larvae in contaminated soil penetrate the skin (often via bare feet), then migrate through the body, eventually reaching the intestine; "Ground itch" is caused by the larvae penetrating the skin.
Larvae in contaminated soil penetrate the skin (often via bare feet), then migrate through the body, eventually reaching the intestine; "Ground itch" is caused by the larvae penetrating the skin.
Imagine you're observing an unknown cell under a powerful microscope. You notice it has a distinct nucleus containing multiple linear chromosomes, as well as several membrane-bound structures like mitochondria and a Golgi apparatus. Based on these observations, would you classify this cell as prokaryotic or eukaryotic?
Eukaryotic, because it has a nucleus containing chromosomes and membrane-bound organelles.
A patient is diagnosed with tuberculosis. Why would a standard Gram stain be inadequate for identifying the causative Mycobacterium tuberculosis, and why is the required antibiotic treatment typically prolonged (3-6 months) and with special medications?
Gram stains are inadequate because M. tuberculosis has an acid-fast cell wall containing mycolic acid that resists Gram staining; treatment is prolonged and requires special antibiotics to penetrate this waxy layer and overcome its resistance to destruction.
A hospital needs to ensure all surgical instruments are free of Clostridium species, which are known to form endospores. Why would simple disinfection with water-based cleaners or even boiling the instruments be insufficient to achieve sterility in this case?
Endospores are highly resistant, dormant structures that cannot be killed by disinfection; they require sterilization methods like autoclaving or strong chemical agents to destroy their protective layers.
If there is a dimorphic yeast inside the body during a fungal infection, what might it tell you about the typical conditions (like temperature) it experiences inside the human body compared to its mold form?
Inside the human body, at body temperature (37°C), dimorphic yeasts are typically found in their yeast form.
A pregnant woman is strongly advised to avoid handling cat litter and to ensure all meat she consumes is thoroughly cooked. Explain the reasoning behind these specific precautions.
Toxoplasma gondii can be transmitted through fecal cysts in cat litter and tissue cysts in undercooked meat. If a pregnant woman becomes infected, the parasite can cross the placenta and cause congenital toxoplasmosis in the fetus, leading to severe developmental issues, blindness, or miscarriage.
A person is diagnosed with taeniasis (intestinal tapeworms) after eating undercooked beef, while another person who ingested tapeworm eggs develops neurocysticercosis (larval cysts in the brain). Compare and contrast the severity of these two diseases and explain the key difference in how each infection is acquired.
Taeniasis is typically asymptomatic and caused by ingesting larval cysticerci in undercooked meat (human is definitive host), while neurocysticercosis is a severe disease affecting the brain, caused by ingesting tapeworm eggs (human acts as intermediate host).