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Microbiology Lecture > Exam 2 > Flashcards

Exam 2 Flashcards

(108 cards)

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1
Q

What is gene regulation?

A

It’s how cells decide when and how much of a protein to make.

Example: Your skin cells and your liver cells have the same DNA, but they “turn on” different genes depending on what they need to do.

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2
Q

What is an operon in bacteria?

A

Think of it like a factory with an ‘on/off’ switch, including a promoter, operator, and genes.

  • Promoter: the ‘start’ button where RNA polymerase binds.
  • Operator: a ‘blocker gate’ that can be closed by a repressor.
  • Genes: instructions to make proteins (like enzymes).
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3
Q

What is the Lac Operon example?

A

Bacteria only want to make lactose-digesting enzymes if lactose is around.

If there’s no lactose, the repressor blocks the gene. If lactose is present, it binds the repressor, causing it to fall off and allowing the gene to be read.

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4
Q

What does the Ames Test detect?

A

Whether a chemical causes mutations in DNA.

This can lead to cancer.

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5
Q

How does the Ames Test work?

A

Uses bacteria that can’t grow unless they mutate, specifically they can’t make histidine.

If they start growing after exposure to a suspected mutagen, a mutation occurred.

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6
Q

What is Horizontal Gene Transfer (HGT)?

A

The sharing of DNA between bacteria directly, instead of passing it down to offspring.

There are three types: conjugation, transformation, and transduction.

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7
Q

What is conjugation in HGT?

A

One bacterium builds a tube (sex pilus) to another and sends over a plasmid.

Donor (F⁺) and recipient (F⁻) are required.

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8
Q

What is transformation in HGT?

A

Bacteria pick up DNA floating around them.

The ability to pick up the DNA is called competence.

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9
Q

What is transduction in HGT?

A

Viruses infect bacteria and accidentally carry bacterial DNA from one to another.

Types include generalized and specialized transduction.

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10
Q

What is the lytic cycle?

A

The aggressive mode of a virus where it attaches, penetrates, replicates, assembles, and lyses the host cell.

The host cell dies in this process.

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11
Q

What is the lysogenic cycle?

A

The sneaky mode of a virus where the viral DNA integrates into the host genome and remains dormant until triggered.

The host cell survives until the virus activates.

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12
Q

What are the key differences between the lytic and lysogenic cycles?

A

Lytic: viral DNA separate, host dies, immediate activation. Lysogenic: viral DNA integrated, host survives, activation requires a trigger.

See detailed comparison in the text.

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13
Q

What is selective toxicity?

A

The ability to selectively find and destroy pathogens without damaging the host.

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14
Q

What are broad-spectrum antibiotics?

A

Antibiotics that affect a broad range of gram-positive or gram-negative bacteria.

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15
Q

What is a superinfection?

A

Growth of a target pathogen that has developed resistance to the antibiotic.

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16
Q

True or False: Broad-spectrum antibiotics are always more effective than narrow-spectrum antibiotics.

A

False

Broad-spectrum antibiotics can lead to superinfections.

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17
Q

How does a low concentration of penicillin G select for penicillin-resistant bacteria?

A

It allows resistant bacteria to survive and multiply while sensitive bacteria are killed.

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18
Q

What are antibiotics?

A

Chemicals that kill or stop the growth of bacteria (not viruses!).

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19
Q

List major ways antibiotics work

A
  • Inhibit cell wall synthesis
  • Inhibit protein synthesis
  • Inhibit DNA/RNA synthesis
  • Disrupt cell membranes
  • Block metabolite synthesis
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20
Q

What is antibiotic resistance?

A

The ability of bacteria to survive and multiply despite the presence of antibiotics.

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21
Q

What are the mechanisms of antibiotic resistance?

A
  • Efflux pumps
  • Blocked entry
  • Enzymatic inactivation
  • Target modification
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22
Q

What can lead to antibiotic resistance?

A
  • Random mutations
  • Horizontal gene transfer
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23
Q

What are some solutions to antibiotic resistance?

A
  • Limit use of broad-spectrum drugs
  • Combine drugs
  • Phage therapy
  • Vaccine use
  • New funding models
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24
Q

What are viruses?

A

Acellular infectious agents that need to invade a host cell to reproduce.

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25
What is the basic structure of a virus?
* Nucleic Acid * Capsid * Envelope (optional) * Spikes
26
How do viruses reproduce?
* Attachment * Entry * Biosynthesis * Assembly * Release
27
What is the difference between lytic and lysogenic cycles in terms of host outcome?
Lytic: host cell bursts and dies. Lysogenic: host survives for a while.
28
What are cytopathic effects?
refers to the structural changes or morphological alterations in host cells caused by viral infection. These changes can range from Cell death, fusion of cells, loss of function, immune evasion. CPE is a valuable diagnostic tool for identifying viral infections and can be used to monitor the progression of viral infections
29
What are oncogenic viruses?
Viruses that can cause cancer. ## Footnote Examples: HPV, Hepatitis B, HTLV.
30
List three types of molecules detected in COVID tests
* RT-PCR test: pieces of RNA genome * Antigen test: viral proteins * Antibody test: antibodies
31
What is pathogenicity?
The ability to cause disease.
32
What is virulence?
The severity of the disease caused.
33
What are common portals of entry for pathogens?
* Mucous membranes * Skin * Parenteral route
34
What is adherence in the context of pathogens?
The ability of pathogens to stick to host cells.
35
What is pathogenicity?
Ability to cause disease.
36
What is virulence?
Severity of the disease caused.
37
What are the portals of entry for pathogens?
* Mucous membranes: respiratory, GI, urogenital * Skin: broken skin, hair follicles * Parenteral route: punctures, bites, injections, surgery
38
What is the most common portal of entry for pathogens?
Mucous membranes.
39
What are adhesins/ligands?
Proteins or glycoproteins on fimbriae or membrane that bind to specific host receptors.
40
What is the consequence of blocking adhesion in pathogens?
Preventing infection.
41
True or False: A drug binding mannose on human cells would prevent bacterial adhesion.
True.
42
What is the function of the capsule in Strep. pneumoniae?
Evades phagocytosis.
43
What is the function of M protein in Strep. pyogenes?
Blocks phagocytosis.
44
What does mycolic acid do in Mycobacterium tuberculosis?
Resists digestion in phagocytes.
45
What is antigenic variation?
Changes surface proteins to dodge immune memory.
46
What is the function of Opa protein in Neisseria gonorrhoeae?
Tight binding to host cells.
47
What does coagulase do?
Forms clots — hides bacteria from the immune system.
48
What is the function of kinase in bacteria?
Breaks down clots — spreads infection.
49
What does hyaluronidase do?
Digests hyaluronic acid (cell glue) — spreads through tissues.
50
What is the function of collagenase?
Breaks collagen barriers — deeper tissue penetration.
51
What does IgA protease destroy?
Mucosal antibodies.
52
What is the primary characteristic of biofilms?
70% of infections involve biofilms.
53
What do biofilms resist?
* Antibiotics * Disinfectants * Immune cells
54
What is the function of siderophores?
Steal iron from host proteins (e.g., transferrin).
55
What are exotoxins primarily produced by?
Mostly Gram positive bacteria.
56
Are exotoxins secreted?
Yes.
57
What is the target specificity of exotoxins?
High — neurotoxins, enterotoxins, etc.
58
Are exotoxins heat-stable?
Usually heat-sensitive.
59
Can exotoxins be toxoids?
Yes (used in vaccines).
60
What are endotoxins produced by?
Gram-negative bacteria only.
61
Where are endotoxins located?
Lipid A of LPS (outer membrane).
62
When are endotoxins released?
During death or division.
63
What effects do endotoxins have?
* Fever * Hypotension * Shock
64
What is epidemiology?
The science that studies where and how diseases spread in populations.
65
What is the formula for incidence rate?
(Number of new cases / Total population) × 100,000
66
What does ID₅₀ represent?
Number of microbes needed to infect 50% of a sample.
67
What does a lower ID₅₀ indicate?
More virulent the pathogen.
68
What does LD₅₀ represent?
Amount of toxin or pathogen needed to kill 50% of a population.
69
What does a lower LD₅₀ indicate?
More toxic the substance.
70
What is the RT-PCR test used for?
Detects viral RNA (the virus’s genetic material).
71
What is the advantage of the antigen test?
Faster results (~15 min) but more false negatives.
72
What does the antibody test indicate?
Past infection, not current.
73
What is the function of interferons?
Signaling proteins made by virus-infected cells that help protect neighboring cells by alerting them to strengthen their antiviral defenses
74
What is the basic virus life cycle?
* Attachment * Entry * Uncoating * Replication & Transcription * Translation * Assembly * Release
75
What characterizes the lytic cycle?
Virus immediately hijacks host to make more viruses and ends with cell lysis (death).
76
What characterizes the lysogenic cycle?
Virus DNA becomes part of host DNA (prophage) and is dormant.
77
What is the AMES test used for?
Detecting mutagens.
78
How do bacteria become resistant to antibiotics?
* Mutation * Gene Transfer (Conjugation, Transduction, Transformation)
79
What are the main mechanisms of antibiotic resistance?
* Efflux pumps * Blocked entry * Enzymatic destruction/modification
80
What is conjugation in the context of plasmid exchange?
A mechanism of genetic exchange where plasmids are transferred between bacteria.
81
What is transduction?
The process of transferring genetic material between bacteria using viruses.
82
What is transformation in bacteria?
The uptake of DNA from the environment by bacteria.
83
What are efflux pumps?
Mechanisms in bacteria that pump drugs out of the cell.
84
What does blocked entry refer to in bacterial resistance?
Alteration of porins in the bacterial membrane to prevent drug entry.
85
What is enzymatic destruction/modification in bacteria?
The use of enzymes, like beta-lactamases, to break down antibiotics.
86
What is target alteration in bacteria?
Mutations in bacterial targets of antibiotics, such as ribosomes or enzymes.
87
True or False: Taking antibiotics for viral infections contributes to antibiotic resistance.
True
88
What are the key aspects of combination therapy?
Using two drugs together to enhance effectiveness, e.g., amoxicillin + clavulanic acid.
89
What is phage therapy?
A treatment that uses viruses specific to bacteria to target infections.
90
What are lysins in the context of bacterial treatment?
Purified enzymes produced by bacteriophages to break down the bacterial cell wall. Lysins are highly specific to certain bacterial species, making them a promising tool in developing targeted antibacterial therapies.
91
What is economic restructuring in antibiotic development?
A model where companies are paid for access to drugs rather than volume sold.
92
List three prevention strategies to combat antibiotic resistance.
* Better sanitation * Limiting antibiotic use in farming * Vaccines to prevent infections
93
What are capsules in bacteria?
Polysaccharide structures that help bacteria evade phagocytosis.
94
What role does the M protein play in Streptococcus pyogenes?
Prevents phagocytosis and aids in bacterial attachment.
95
What is mycolic acid?
A waxy coat in Mycobacterium tuberculosis that resists digestion inside phagocytes.
96
What is the significance of antigenic variation in bacteria?
Bacteria change surface proteins to avoid detection by the immune system.
97
What function does hyaluronidase serve?
Breaks down hyaluronic acid, facilitating tissue penetration.
98
What does collagenase do?
Breaks down collagen, a component of connective tissue.
99
What is the function of streptokinase/staphylokinase?
Breaks down clots (fibrin) to aid bacterial spread.
100
Fill in the blank: Coagulase forms ________ to hide from the immune system.
clots
101
What are biofilms?
Communities of microbes that stick to surfaces and each other, surrounded by a protective matrix.
102
Why are biofilms dangerous?
* Antibiotic resistance * Immune evasion * Chronic infections
103
Give an example of a biofilm-related infection.
* Staphylococcus aureus on catheters * Pseudomonas aeruginosa in cystic fibrosis * Dental plaque
104
What are exotoxins?
Toxic proteins secreted by living bacteria, mostly Gram-positive.
105
What are endotoxins?
Lipid A from LPS, found only in Gram-negative bacteria, released upon cell death.
106
What is the pyrogenic response to endotoxins?
* Macrophage eats Gram-negative bacteria * Releases endotoxin * Triggers cytokine release leading to fever
107
What is the LAL assay used for?
To detect endotoxins in medical products using horseshoe crab blood.
108
What is the difference between food infection and food intoxication?
* Food infection: live bacteria ingested, symptoms take longer * Food intoxication: pre-formed toxins ingested, symptoms appear rapidly

Microbiology Lecture (5 decks)

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