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BIO 425: Microbiology > Lecture 6/7: Growth Control and Molecular Biology > Flashcards

Lecture 6/7: Growth Control and Molecular Biology Flashcards

1
Q

What are the mechanisms of drug resistance?

A
  1. Impermeability - drug can’t get into cell
  2. Efflux - infected cell ejects drug from cell w/ enzyme
  3. Inactivation - enzyme degrades drug
  4. Mutation in target - drug target mutates
  5. Absence of target
  6. Alternative Biochem pathway - cell uses different pathway to get around target of drug
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2
Q

What are the origins of the evolution of drug resistance?

A

Drugs are produce by microorganisms b/c the microorganisms must be able to resist their own antibiotics There is no universal antibiotic Antibiotics also function as signaling molecules

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3
Q

How has antibiotic resistance spread?

A

Overuse

  • 20 percent of patients need antibiotic treatment
  • 80 percent of patients receive antibiotic treatment
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4
Q

How is gonorrhea a case study of antibiotic resistance?

A

Penicillin used from 1940-1990

Ciprofloxacin used in early 1990s

Ceftriaxone used in late 1990s

Antibiotics only effective as long as we have a continuous supply of new types of antibiotics

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5
Q

How is antibiotic resistance spread through non-medical overuse?

A

50-70 percent of antibiotics used for livestock/agriculture

We select for antibiotic-resistant bacteria by creating these antibiotic rich habitats

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6
Q

What is an ‘‘invincible’’ pathogen? What is an example?

A

Resistance to all known microbial agents

MRSA -Methicillin-Resistant Staphylococcus aureus

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7
Q

How do we reverse antibiotic resistance?

A

decrease usage = decrease selection = decrease prevalence of resistance

-large scale coordinated effort

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8
Q

How do we deal with antibiotic resistance? What is the economic paradox of antibiotics that makes dealing with it less likely?

A

We can discover and develop new antibiotics

Economic paradox is

  • low return on investment b/c not a lifelong medicine
  • loss of value over time b/c resistance of development
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9
Q

How do we discover new drugs?

A
  1. New analogs of existing compounds
  2. Computer drug design
  3. Natural products
  4. Drug combinations
  5. Bacteriophage therapy
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10
Q

How do we use new analogs of existing compounds to search for new antimicrobial drugs?

A

Semisynthetic approach

-changing functional groups on existing compounds

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11
Q

How do we use computer drug design to search for new antimicrobial drugs?

A

Computer based design of new molecule to mimic/outcompete normal substrate of disease enzyme

  • competitive inhibition
  • must know very detailed information about disease like shape/structure
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12
Q

How do we use natural products to search for new antimicrobial drugs?

A

Most antibiotics found in soil

  • actinomycetes found in soil and important for antibiotic production
  • more difficult but can find antibiotics in marine sediment
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13
Q

How do we use drug combinations to search for new antimicrobial drugs?

A

Using an antibiotic+compound inhibiting resistance

  • finding something that inhibits the mechanism for antibiotic resistance and combining it with an antibiotic
  • eg. efflux pump inhibitor + antibiotic
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14
Q

How do we use bacteriophage therapy to search for new antimicrobial drugs?

A

We use viruses to destroy specific pathogens

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15
Q

What are the functions of the different genetic elements?

A

Replication - DNA to DNA

Transcription - DNA to RNA

Translation - RNA to protein

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16
Q

What is the function of DNA/RNA?

A

DNA - deoxyribonucleic acid

  • genetic blueprint for cell
  • information replication and storage

RNA - ribonucleic acid

  • converts blueprint to amino acids
  • information processing
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17
Q

What is the structure of DNA?

A

Double stranded

  • sugar-phosphate backbone
  • held together by Nitrogenous bases

Antiparallel

-5’ to 3’ and 3’ to 5’

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18
Q

What are the different types of grooves in the DNA double helix pictured?

A

Major groove and Minor grooves

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19
Q

How is DNA packaged into the cell? What enzyme is responsible for this?

A

DNA Supercoiling

-twisting DNA into coils takes up less space

Topoisomerases are responsible for this

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20
Q

What are the types of Topoisomerases?

A

Class I Topoisomerases

-Single stranded break

Class II Topoisomerases

  • Double-stranded break
  • eg DNA Gyrase
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21
Q

DNA is supercoiled in order to fit into cells. What needs to happen in order to access the DNA?

A

Relaxation

-for DNA transcription and replication

22
Q

What are the differences between chromosomes and plasmids?

A

Chromosomes

  • main genetic element
  • large
  • Essential genes (housekeeping)

Plasmids

  • additional genetic element
  • small
  • Non-essential genes
23
Q

How do chromosomes and plasmids transmit genetic material?

A

Chromosomes - vertical transmission

-parent to offspring

Plasmids - Vertical+Horizontal transmission

  • transmit via pili
  • don’t need to be same species
24
Q

What are R-Plasmids? What is it called when R-Plasmids are transferred to other bacteria? What are some examples?

A

R-Plasmids are resistance plasmids that confer antibiotic resistance

When transferred to other bacteria it is called CONJUGATION

Examples are B-lactamases and rRNA methylases

25
What are virulence plasmids?
Plasmids, or secondary genetic material, that make a particular bacteria a pathogen They confer 1. Ability to colonize the host 2. Ability to produce toxins Different types of same microbe can be dangerous or good depending on virulence plasmids
26
What molecules and enzymes are involved in DNA replication?
**Molecules** - DNA Template - Primer-gets new strand started - Nucleotides-used to build new strand **Enzymes** - DNA Helicase-unwinds DNA - Primase-synthesize RNA primer on ssDNA - DNA Polymerase
27
What is significant about prokaryotic chromosomes?
They are circular - so there are two replication forks resulting in fast DNA replication - called bidrectional replication
28
What is Polymerase Chain Reaction?
DNA replication in vitro -not entire genome, only pieces
29
What are the molecules and enzymes involved in PCR?
Molecules - DNA Template - Primer - Nucleotides Enzymes - Heat instead of DNA Helicase - Designed and added primase instead of RNA primase - DNA polymerase III
30
What are the steps of PCR?
1. **Denaturing** - Heat to 94 degrees Celsius - dsDNA to ssDNA 2. **Anneailng** - Cool to 55 degrees Celsius - Primers bind 3. **Extension** - Heat to 72 degrees Celsius - Polymerase builds DNA 4. **Repeat** - 25-35 cycles - DNA Doubles each cycle=exponential growth
31
What machine is responsible for PCR?
Thermocycler machine
32
What are the applications of PCR?
High output of information very fast -DNA sequencing, barcoding, identifying microbial communities Very sensitive
33
What are the nitrogenous bases of DNA/RNA?
DNA -Adenine, Thymine, Cytosine, Guanine RNA -Adenine, Uracil, Cytosine, Guanine
34
What is different about Uracil?
- Similar to cytosine, 1 func group difference - Less stable than thymine - high mutation rate w/ RNA due to Uracil
35
What is the structure of RNA?
Single stranded - one backbone The secondary structure is formed by hydrogen bonds -forms non-linear stems and loops
36
What are the types of RNA?
**mRNA** - genetic info carrier - from genome to ribosome **tRNA** -codes for protein synthesis **rRNA** -form ribosomes, site of protein synthesis
37
What molecules and enzymes are involved in the initiation step of transcription?
Molecules - promoter Enzymes/Proteins - Sigma factor - binds to DNA at promoter region to recruit RNA polymerase - RNA polymerase binds to sigma factor to begin transcription
38
What molecules and enzymes are involved in the elongation step of transcription?
RNA Polymerase begins transcription - sigma factor released - RNA chain grows
39
What molecules and enzymes are involved in the termination step of transcription?
**RNA Polymerase reaches the termination site** - Chain growth stops - RNA Polymerase and newly synthesized mRNA are released from DNA template **Termination controlled by Signal DNA sequences** 1. Inverted repeats 2. Run of Uracils
40
What is different about transcription in archaea than in bacteria?
1. RNA Polymerase structure 2. Promoter region 3. Presence of introns
41
What is significant about RNA Polymerase structure in archaea?
- More similar to eukaryotes - more complex than bacteria
42
Do arachaea have introns?
Yes but rare - absent in bacteria - present in eukaryotes
43
What are the functions of transcription, replication, translation?
**Replication and Transcription** - nucleic acids to nucleic acids - DNA to DNA OR DNA to RNA **Translation** -nucleic acids to proteins
44
What is tRNA?
**THE TRANSLATOR** - Links codons in mRNA to Amino Acids in proteins - short, ssRNA **Gets its secondary structure from internal base pairing** **Anticodon** **-**Complimentary to mRNA codon **Has Amino Acid binding site** **-**attaches corresponding amino acid
45
What is the initiation step of translation?
Form Ribosome-mRNA Complex mRNA binds at Ribosome binding site -recognizes the Shine-Dalgarno Sequence
46
What is the elongation step of translation?
Match tRNAs and Add Amino Acids Amino Acids are linked by Peptide Bonds
47
What is the Termination step of translation?
Release factors release newly synthesized protein Recognize stop codon
48
What are the levels of protein structure?
**Primary** - Amino Acid sequence -formed by translation **Secondary** - alpha helix or beta sheet - formed by H-bonds - stability, helix more stable than sheet b/c more H-bonds **Tertiary** - 3D Structure -formed by hydrophobic interactions, H, ionic, and disulfide bonds **Quaternary** - greater than 1 polypeptide -each polypeptide called a subunit
49
What does protein structure determine?
Protein function - loss of structure=loss of function - primary structure will remain even after denaturing
50
What are molecular chaperones, chaperonins?
Assist in protein folding -either newly synthesized or partially denatured proteins

BIO 425: Microbiology (22 decks)

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