Microbial Genetics (Micr340)

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Microbial Genetics (Micr340)

• Lecture 9
• Lytic Bacteriophages (I)

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Definitions

• Bacteriophages - viruses that infect bacteria
  (also called phages for short)
• Capsids - isocahedral heads of bacteriophages
  made of viral genome plus protein coats (for
  protection)
• Plaques - holes (killing of bacterial cells by
  phages) on a lawn of bacterial growth

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Bacteriophage Lytic Cycle

• Absorption to cell
• Viral genome injected into cell
• Viral gene transcription
• Early genes
• Middle genes
• Late genes
• Assembly of viral particles
• Cell lyse

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Bacteriophage lytic cycle
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Regulation during lytic cycle
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Phage T4

• Large virus
• Well studied
• A new sigma factor
• Replication-coupled transcription

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Phage T4 replication-coupled transcription
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Phage DNA replication

• Single-stranded circular DNA
• Linear DNA that forms concatemers

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Single-stranded circular DNA- phage f1
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Single-stranded circular DNAM13
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Single-stranded circular DNAM13
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M13 based cloning vector
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M13 based cloning vectorUse in site-specific
Mutagenesis
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Linear DNA that forms concatemers T7
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Linear DNA that forms concatemers T4