micro exam 4

Efflux pumps

Pump antibiotics out of the cell so they cannot reach effective levels

Reduced permeability

Prevent antibiotics from entering the cell (e.g., altered porins)

Enzymatic inactivation

Break down or chemically modify the antibiotic so it no longer works

Target modification

Change the antibiotic's binding site so the drug cannot attach

Metabolic bypass

Use an alternative pathway to bypass the antibiotic's effect

What are the basic structural components of all viruses?

A nucleic acid core (DNA or RNA) and a protein capsid

How do DNA and RNA viruses differ in terms of genome structure?

RNA- Helical capsid, Helical capsid within envelope

DNA- Icosahedral head: helical tail, Icosahedral capsid

What is a capsid, and what is its function?

a protein coat that protects the viral genome and helps with host infection

What is the role of a viral envelope?

a lipid membrane from the host that helps with entry into host cells and immune evasion

Define host range and tissue tropism

Host range = types of organisms a virus infects

Tissue tropism = specific tissues infected within a host

Why are viruses considered obligate intracellular parasites?

They must use host cell machinery to reproduce

What are the key steps in the lytic cycle of bacteriophages?

Attachment

Penetration

Synthesis

Assembly

Release

How does the lysogenic cycle differ from the lytic cycle?

In lysogenic cycle virus DNA integrates into host genome and does not immediately kill the cell.

What is a prophage?

viral DNA integrated into the host genome

How are viruses classified according to the Baltimore classification system?

Based on genome type and how they produce mRNA

What are prions and how do they cause disease?

infectious misfolded proteins that cause brain diseases (Proteinaceous infectious particles)

List the 3 examples of Prion diseases

Mad cow disease (BSE)

Scrapie

Creutzfeldt-Jakob disease

What are viroids and how do they differ from viruses?

Tiny naked circular RNA molecules (no protein coat) that infect plants.

What are the steps involved in binary fission?

Cell enlarges

DNA replicates

Septum forms

Cell splits into two

What is generation time (doubling time)?

time required for one cell division (doubling)

How does exponential growth occur in microbial populations?

Exponential growth occurs when cells double continuously at a constant rate

What are the four phases of the bacterial growth curve?

Lag

Log (exponential)

Stationary

Death

What characterizes the lag phase?

Cells adjust and prepare for growth

What occurs during the log (exponential) phase?

rapid cell division and exponential increase

What happens during the stationary phase?

growth rate = death rate due to limited nutrients

What factors contribute to the death phase?

cells die due to waste buildup and lack of nutrient

How can microbial growth be measured using culture-based methods?

viable plate count (colony counting)

What are non-culture-based methods for measuring microbial growth?

Turbidity (cloudiness)

Microscopic counts

Flow cytometry

How does a chemostat maintain continuous microbial growth?

Keeps growth continuous by adding nutrients and removing waste/cells. Maintains the culture in a biochemically active state and prevents it from entering the death phase.

What are the main mechanisms of action of antibiotics?

Cell wall inhibition

Protein synthesis inhibition

DNA/RNA inhibition

Membrane disruption

Metabolic inhibition

How do antibiotics that inhibit cell wall synthesis work?

Cell wall inhibitors weaken the wall → cell bursts

Provide examples of antibiotics that inhibit cell wall synthesis

Penicillin

Amoxicilin

Ceftriaxone

How do antibiotics that inhibit protein synthesis work?

Blocks ribosomes --> prevents growth/replication

Provide examples of antibiotics that inhibit protein synthesis

Doxycycline

Azithromycin

Gentamicin

How do antibiotics that inhibit DNA or RNA synthesis function?

Stops replication or transcription

Provide examples of antibiotics that inhibit DNA or RNA synthesis

Ciprofloxacin

Levofloxacin

Rifampin

How do antibiotics disrupt the bacterial cell membrane?

causes leakage and death

Provide examples of antibiotics that disrupt the bacterial cell membrane

Daptomycin

Colistin

How do antibiotics inhibit metabolic pathways?

blocks essential biochemical reactions

Provide examples of antibiotics that inhibit metabolic pathways

sulfa drugs (folate synthesis inhibitors)

What is antibiotic resistance?

Bacteria adapt and then no longer respond to antibiotics

How does mutation contribute to antibiotic resistance?

Mutation can change target proteins → antibiotic no longer works

What role does natural selection play in antibiotic resistance?

Natural selection allows resistant bacteria to survive and reproduce

How does gene flow contribute to the spread of resistance?

Gene flow spreads resistance through horizontal gene transfer

What are common mechanisms bacteria use to resist antibiotics?

Enzyme destruction of drug

Target modification

Efflux pumps

Reduced permeability

How does overuse of antibiotics contribute to resistance?

Overuse of antibiotics increases selection pressure for resistant strains

What are anti-virulence therapies and how do they work?

Block bacterial harmful traits instead of killing them.

What are quorum sensing inhibitors and how do they affect bacterial behavior?

Prevent bacterial communication and coordination

What is drug repurposing in the context of antimicrobials?

Using existing drugs for new antimicrobial uses

What are bacteriophages and how are they used therapeutically?

Viruses that infect bacteria and can be used to kill specific bacterial infections

What are antimicrobial peptides and how do they function?

Destroy bacterial membranes or disrupt cell function

How do microbiome-based therapies help fight infections?

Restore healthy bacteria to outcompete pathogens