Eukaryotic Microbes
A single-celled protist extends temporary projections of its cytoplasm to move and capture food. What group does it belong to?
Amebas
A virus can infect liver cells but cannot infect nerve cells, even though both cell types belong to the same host. What is this preference called?
Tissue Tropism
Explain the difference between antigenic drift and antigenic shift.
-Antigenic drift: Gradual accumulation of small mutations in viral genes that change viral surface antigens.
- Antigenic shift: A major antigenic change caused by reassortment of genome segments when different influenza strains infect the same cell.
This is the lowest temperature at which all microorganisms in a liquid culture are killed in 10 minutes.
Thermal death point
How do sulfonamides work to affect intermediary metabolism?
Compete with PABA and inhibit an enzyme involved in folic acid synthesis. This prevents bacteria from producing folate needed to make nucleotides for DNA synthesis.
A fungus grows as mold at 25°C but changes into a yeastlike form at 37°C. What is this phenomenon called, and why is it clinically important?
Dimorphism
What are the virus-encoded proteins embedded in the viral envelope called, and what is their primary function?
Viral spike proteins (glycoproteins)
Define latent infection and give a good example.
A viral infection in which the virus remains dormant in host cells and can reactivate later. Example: herpes simplex virus (HSV).
What type of sterilization is specifically used for Clostridium botulinum endospores
Commercial sterilization! kills all spores without altering the quality of the food.
What are the drugs that work by poking holes in the bacterial cytoplasmic membrane to kill bacteria?
Gramicidin
Polymixin
A microorganism has a nucleus, linear chromosomes, and membranous organelles. However, it lacks mitochondria and is closely related to fungi. Identify the organism group and explain why its lack of mitochondria makes it unusual.
Microsporidians
Explain the differences between the lytic cycle and the lysogenic cycle. (Bonus: name the specific example listed in lecture for lysogeny)
Lytic cycle: The bacteriophage attaches to a bacterial cell, injects its genetic material, replicates its genome, produces viral proteins, assembles new phages, and eventually lyses (destroys) the bacterial cell to release new viruses.
Lysogenic cycle: The bacteriophage integrates its DNA into the bacterial chromosome, where it is called a prophage. The viral DNA is replicated along with the bacterial DNA as the host cell divides without immediately destroying the cell.
Identify HPV's structural characteristics and explain how its genomic integration can contribute to cancer development.
Integration into the host genome can increase the expression of E6 and E7 oncogenes.
These proteins interfere with normal cell-cycle regulation, promoting cellular transformation and potentially cancer.
A bacterial population begins with 1,000,000 cells. If the D-value is 2 minutes, how many cells remain after 6 minutes?
1,000 cells remain.
Starting population: 1,000,000
D-value: 2 minutes
Total time: 6 minutes
Number of reductions: 3
1,000
A patient takes an antibiotic for pneumonia. Most susceptible bacteria die, but a naturally occurring resistant mutant survives, reproduces, and causes the infection to return. Explain how this resistance developed.
This is natural selection
A random mutation creates a bacterium that is resistant to the antibiotic.
The antibiotic kills the susceptible bacteria but does not kill the resistant mutant.
The resistant bacterium survives and reproduces.
Its offspring inherit the resistance, increasing the resistant bacterial population
Two protozoan cells temporarily join and exchange genetic material rather than simply dividing into daughter cells. What type of sexual reproduction is occurring?
Conjugation
A scientist infects bacterial host cells with bacteriophages and monitors viral production over time.
Explain the difference between the eclipse period and the rise period in the one-step growth curve.
Eclipse period: Newly synthesized viral components are being produced inside the host cell, but complete infectious virus particles are not yet detectable.
Rise period: Newly assembled bacteriophages begin appearing outside the host cells as they are released, often through cell lysis.
Explain how influenza replicates its genome, identify the roles of hemagglutinin (HA) and neuraminidase (NA)
Influenza is an enveloped, segmented, negative-sense, single-stranded RNA virus.
It uses RNA-dependent RNA polymerase to produce positive-sense mRNA and replicate its genome.
HA helps the virus attach to host cells.
Entry occurs through endocytosis.
New viral particles assemble and exit through budding.
NA helps newly formed virions detach from the host cell.
What is the magic bullet concept?
Antibiotics are selectively toxic to bacteria without toxicity to eukaryotic organisms
This antibiotic class binds to penicillin-binding proteins (PBPs), preventing the formation of peptide cross-links in peptidoglycan.
beta-lactam antibiotics
A microorganism has the following characteristics:
It is single-celled.
It is a eukaryote.
It has one or more flagella.
It has a complex parasitic life cycle.
It does not belong to the apicomplexan group.
Identify the most likely protozoan category and explain which characteristics support your answer.
Flagellates (trypanosomes)
Briefly describe how each group in the Baltimore model synthesizes mRNA. Include each group's specific enzymes.
group 1: dsDNA --> mRNA
group 2: ssDNA --> dsDNA --> mRNA
group 3: dsRNA--> RNA-dependent RNA polymerase --> mRNA
group 4: ssRNA(+) --> RNA-dependent RNA polymerase --> mRNA
group 5: ssRNA (-) --> ssRNA (+) --> RNA-dependent RNA polymerase --> mRNA
group 6: ssRNA (-) --> reverse transcriptase --> dsDNA--> mRNA
group 7: dsDNA --> mRNA --> reverse transcriptase --> dsDNA for the viral genome
Explain the stages of HIV replication (Bonus: can you name a drug that works to block HIV replication and where it works?)
Attachment and entry: HIV spike proteins bind host-cell receptors and coreceptors, followed by fusion with the host membrane.
Reverse transcription: Reverse transcriptase converts viral RNA into DNA.
Integration: Integrase inserts viral DNA into the host chromosome.
Transcription and translation: Host machinery produces viral RNA and proteins.
Assembly: Viral components assemble at the host-cell membrane.
Budding and maturation: New virions bud from the cell, and viral protease cleaves polyproteins to produce mature infectious virions.
Define the Minimum Inhibitory Concentration (MIC) as well as the Kirby-Bauer assay and the Zone of inhibition
also
Define the minimal bactericidal concentration (MBC)
Minimum inhibitory concentration (MIC): Lowest concentration of an antibiotic that prevents visible bacterial growth.
Kirby-Bauer assay: Disk diffusion test used to determine bacterial susceptibility to antibiotics by placing antibiotic disks on an agar plate inoculated with bacteria.
Zone of inhibition: Clear area surrounding an antibiotic disk where bacterial growth has been prevented. Its size helps determine bacterial susceptibility.
A bacterium survives antibiotic treatment by actively transporting the drug out of the cell before it can reach an effective concentration. Identify this resistance mechanism.
Efflux pump