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68 Cards in this Set
- Front
- Back
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Twort
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Worked on Micrococci and Bacteriophages
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d'Herelle
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Lysis of Dysentery Causing Bacteria by a Bacteriophage
Researched Phage as Therapy for bacterial Infections (Used phage to cure bubonic plague in 4 people) He Injected Phage Into Lymph Nodes |
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American Phage Group
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Delbruck, Luria, and Hershey Were Members
One-Step Growth Experiments (Plaque Assays) They Got The Nobel Prize For Replication Mechanism and Genetic Structure of Viruses |
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Phage Structure
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Capsids or Icosahedral Heads
Elaborate Tails (Necessary for Cell membrane/wall penetration) |
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MS2
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Small Bacteriophage with no tail
Propagated from E. coli Small Phage = 2 Protein Types Contains only 4 Genes Icosahedral |
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T4
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Enterobacteriophage Infects E. coli
Very Large Genome Large Phage = 20 Protein Types Contains Over 200 Genes Icosahedral-Myoviridae 1st Genome Ever Sequenced |
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Phage Genome
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DNA or RNA Depending on Type
Length of Nucleic Acid Indicates Complexity |
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Where are Bacteriophage Found?
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Everywhere!
Waste-Water Treatment Facilities as Well |
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Bacteriophage Infection Steps
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Absorb to Surface Receptor of Bacterial Cell
Penetration of Genome Through Tail Tube into Host Cell Phage Circularizes DNA (Protects From Nucleases) Phage Parts Are Produced and Assembled Lysozyme Packaged into Tail Base Plate Phage Released From Cell |
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Types of Phage Infection
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Lytic or Lysogenic (Temperate)
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Lytic Phage Infection
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Key Enzyme: Holin
Cell Destroyed By Release of Phage |
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Lysogenic (Temperate) Infection
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Genome Integrates Into Host's Chromosome
Host Cell Not Killed Integrated Phage Genome Known as "Prophage" |
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The Lytic Cycle
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DNA Injection->Early Genes Transcribed/Translated->DNA Replication Begins->Late Genes Transcribed/Translated->DNA Packaged Into Head and Tails Attach->Lysis of Host Cell
Takes Less Than 1 hr (For Most Phage) |
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Early Genes (Lytic Cycle)
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RNA Transcription by Host RNA Polymerase Begins Immediately.
Genes Encode DNA Polymerase, Primase, DNA Ligase, and Helicase |
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Late Genes (Lytic Cycle)
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mRNA Transcribed From Remaining Phage Genes
Genes Encode for Head and Tail Assembly |
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How Many Phage Are Produced by a Single Infecting Phage?
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Hundreds
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Lysogeny
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Phage in This Type is "Temperate" Phage
Phage DNA Known As ProPhage Bacteria Harbouring Prophage is The "Lysogen" |
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How Do You Know If A Cell Contains A Prophage?
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If The Cell Is Immune To Other Phage Of The Same Kind
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Defective Prophages
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Phage Which Can No Longer Become Infective Due To Deletion of Essential Genes
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Associated Bacterium:
Beta Phage CTX T12 H-19B |
Corynebacterium diphtheria and Clostridium botulinum (Botulinum Toxin)
Vibrio cholerae Streptococcus pyogenes Escherichia coli (For Shiga-Like Toxins) The Presence of These Phage Make The Bacteria Pathogenic |
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Lambda Phage
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Carried Genes which Allow E. coli Host Serum to Become Resistant and Survive Macrophage
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E. coli Shiga Toxins
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Lambda and Lambda-Related Phage Make E. coli Pathogenic by Encoding Toxins Called "Shiga Toxins"
Shiga Toxins First Described in Shigella dysenteriae Composed of 2 Subunits (A/B) Lead To HUS |
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Shiga Toxin Subunit B
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Helps Subunit A Enter The Endothelial Cell
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Shiga Toxin Subunit A
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Removes a Certain Adenine Base From the 28s rRNA and Blocks Translation.
Interferes With Binding of Translation Factor EF-1a |
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Shiga Toxins (2 Groups)
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stx1 is Encoded in Chromosome of S. dysenteriae and Ricin Toxin in Plants
stx2 Found in Prophage of E coli stx2 is in More Serious Human Diseases |
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Diphtheria
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Pathogenic Corynebacterium Are Lysogenic for Beta Phage Which Carry Genes for 'tox' (Diphtheria Toxin).
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Diphtheria Toxin
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Only Produced in Eukaryotic Hosts
It's an Enzyme That Kills Eukaryotic Cells by Attaching an Adenosine Diphosphate To Translation Factor EF-2 |
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Cholera
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Single-Stranded Filamentous Phage (CTX)
Phage Enters Cell Through the Tol Channel by Attaching a Pilus |
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Cholera Toxin Genes
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ctxA and ctxB
Encode for an AB Toxin B Subunit Helps A Subunit Enter the Eukaryotic Cell |
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Botulism and Tetanus
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These Toxins are Encoded by Lysogen-forming Phage.
Both cleave the same neuronal Protein (Synaptobrevin) in the exact same amino acid sequence |
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SS RNA Bacteriophages
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Leviviridae: Linear Genome..+ Sense
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Leviviridae
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Icosahedral Capsid Made From 180 Copies of Coat Protein Arranged in a T=3 Icosahedral Shell
Makes 4 Virus Coded Proteins: Coat Protein, Maturation Protein, Lysis Protein, and RNA Replicase 2 Genera: Levivirus and Allolevivirus |
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Genus Levivirus
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f2
MS2 R17 |
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Genus Allolevivirus
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Qb (Enterobacteriophage)
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F-Pilus
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Filamentous Structures that Allow F+ Bacteria to Transfer Part of Their Chromosome to F- Bacteria
Found in F+ Males..Conjugative Bacterial Plasmid |
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Loeb and Zinder
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Discovered RNA Phage
Looked at Sewage Samples (NYC) Plaques on F+ but not F- Bacteria |
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f2
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Phage which creates plaques on F+ bacteria but not F- bacteria
Source for pure mRNA |
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RNA Phage
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Found Wherever E. coli is Found
Found in Sewage Samples Some of The Simplest Viruses Used To Detect Enteroviruses in Drinking Water |
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Two Genera of RNA Phage
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Supergroup A (MS2 Levivirus)
Supergroup B (Qb Allolevivirus) |
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RNA Phage Supergroup A
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Shorter Nucleic Acid (3500)
Code for 4 Proteins: Maturation A Protein, Coat Protein, Lysis Protein, and RNA Replicase |
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RNA Phage Supergroup B
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Longer Nucleic Acid (4200)
Code for 4 Proteins: Maturation A2 Protein, Coat Protein, Readthrough a1 Protein, and RNA Replicase These Phage Have No Lysis Protein bc A2 Carries it Out |
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E. coli RNA Phage
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f2, R17, MS2, Qb
All Have Single-Stranded RNA Genome and Code For 4 Proteins: 2 Head Proteins, a Lysin, and Replicase |
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Phage6
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Isolated from Pseudomonas syringe (Subspecies: phaseolicola)
Double-Stranded Genome 3 Segments: S, M, L |
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Maturation Protein
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Bound to the 3' and 5' ends of the encapsidated RNA
Protects Phage from Degredation by RNase Allows Attachment of Phage to the Side of the F-Pilus |
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What Determines Binding of the Ribosome to the Start Codon For Translation?
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-Base Complementarity bw 16s rRNA and the Shine-Dalgarno Sequence
-Interaction of Anticodon on Initiator fmet-tRNA with AUG on mRNA -Binding of Ribosomal Protein S1 to Pyrimidine Rich S-D seq |
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RNA Secondary Structure
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Regions of Self-Complementary Base Sequences Which Form Stem-Loop Structures
Prevents Interaction of mRNA With Ribosomes Controls Translation of Lysis and Replicase Genes |
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Translation of the Coat Gene
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Disrupts Secondary Structure (Allowing Replicase Translation)
Every Time a Coat Gene is Translated, Stem MJ Base Pairing is Disrupted, Allowing Replicase Translation to Begin |
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Translation of the Lysis Gene
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Depends on Termination of Coat Gene Translation
Once Coat Protein is Released, Ribosome Goes To Either Lysis or Replicase Proteins on mRNA |
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Genome Replication Requirements
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4 Host Proteins and Replicase:
EF-Tu (E. coli Translational E.F.) EF-Ts (E. coli Translational E.F.) S1 Protein (E. coli Small Ribosomal Subunit) Host Factor (E. coli-Unwinds 3' Terminal Hairpin on +RNA Strand) |
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Polymerase
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Active Enzyme, 4 Host Cells Proteins, and Phage-Encoded Replicase
Synthesis of - RNA (From + RNA Template) is From 3' to 5' - RNA to + RNA Does not Require S1 of Host Factor |
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Maturation Protein Translation
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Gene Lies Near End of 5' End of Phage RNA
Ribosomes Only Bind to Maturation Start site on RNA Chains That Are Being Synthesized |
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Bacteriophage T7
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Naked Icosahedral Capsid (T=7)
Linear dsDNA 56 Genes for 59 Proteins Infect Marine Bacteria Ex: T3, H, SP6, gh-1 (All Phage II) |
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T7 Genes
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Described in Classes I-III (Early, Middle, Late)
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HUS
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Hemolytic-Uremic Syndrome
Caused by E. coli Shiga Toxins Signs: Bloody Diarrhea With No White Blood Cells No Fever Abdominal Pain Children Lose Kidney Function |
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T7 Hosts
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Yersinia, Serratia, Klebsiella, and Pseudomonas
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T7 Class I
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"Early"
Located on the Left Side of the Genome Expressed Within 6-8 Minutes of Infection |
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T7 Class II
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"Middle"
Phage DNA Replication |
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T7 Class III
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"Late"
Phage Structural Proteins and Proteins Needed for DNA Maturation and Packing |
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Entry of T7 Phage DNA Into The Cytoplasm
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T7 Phage Binds to LPS
3 Proteins Inserted Through Tail DNA Enters 1st 850 bp on Left Side Transcribed by Host RNA Polymerase (Class I Genes) |
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Class II and Class III Transcription
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Monomeric RNA Polymerase (Product of Class I) is Required For Class II / III Transcription
2 Other Important Genes: 1 Inhibits Host Type I Restriction Endonucleases and 2 Inhibits Host RNA Poloymerase |
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Selected Class II Gene Products
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1.3
2. 2.5 3. 3.5 4. 5. 6. 3 & 6 Degrade Host DNA 1.3, 2.5, 4, & 5 Act as Replication Fork to Make Progeny DNA 2 Inhibits Host RNA Polymerase |
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Selected Class III Gene Products
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8-12, 14-17, 17.5, 18, and 19
8 = Portal Protein 9 = Scaffolding Protein 10 = Capsid Protein 11 = Tail Protein 14-16 = Core Proteins Forming DNA Channel 17 = Tail Fiber 17.5 = Holin Access of Lysozyme to Cell Wall for Lysis 18-19 = Maturation Proteins and DNA Packing |
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Special Features of T7 Family of Phages
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Phage Encoded RNA Polymerase (Specific for Phage Promoters)
Mechanism for Modulating Classic Host Restriction Modification System Ability to Grow Efficiently Only in E. coli (Lack Fertility Plasmid F Making Them F-Restricted Phage) |
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How Do Bacteria Resist Phage Attack?
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Alteration of Cell Wall Receptor
Restriction Endonucleases CRISPR System |
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CRISPR System
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"Clustered Regulatory Interspaced Short Palindromic Repeats" of DNA
Phage Outnumber Bacteria (10:1) First Recognized in E. coli Present in Bacteria and Archaea |
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Components of CRISPR
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Palindromic DNA Sequences (26-71 bp) Are Spaced Apart About 21-48 bp
May be More Than 1 CRISPR in Bacteria/Archaea (As Many As 18!) Usually Located Near cas Genes |
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cas Genes
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Include Members That Encode For Nucleases and Helicases
Allows Host To Integrate Novel CRISPR Spacers |
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Dynamic Flux
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CRISPR Can Change Rapidly, Producing Hypervariability Regions That Set Apart Closely Related Strains From One Another
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