Think of viruses like the ultimate spies in a sci-fi movie!

• Host Target: E. coli, a common bacterium.

• Weapon: Proteins at the tips of its tails that bind to E. coli.

• Mission: Enter the host cell through its tubular tail, then choose one of two paths:
  • Lysogenic Cycle: Like a spy hiding undercover, the viral DNA integrates into the bacterial DNA, waiting for the right moment. No new virus particles are produced. More on this in Section A2.3.4.
  • Lytic Cycle: Like a spy on a destructive mission, the virus reproduces and bursts out of the host cell, killing it. Bacteriophage lambda is like a ferocious warrior when it follows this cycle because it wipes out its host.

• The Catch: If the virus kills all its host cells, it risks dying out itself! Imagine a spy without a mission.

• Bacteriophage Lambda

  • Type: DNA virus
  • Envelope: No
  • Genetic Material: One double-stranded DNA molecule
  • Distinctive Features: Can follow either the lytic or lysogenic cycle
  • Host: E. coli

• COVID-19

  • Type: Coronavirus, an RNA virus
  • Envelope: Yes, like wearing a crown
  • Genetic Material: Single-stranded RNA
  • Distinctive Features: Started a pandemic in 2020! Passed from bats to humans (zoonosis).
  • Host: Humans and possibly other mammals.

  Real World Connection: COVID-19 affected the entire world, closing schools, causing people to wear masks, etc.

• HIV

  • Type: Retrovirus
  • Envelope: Yes
  • Genetic Material: Two single-stranded RNA molecules
  • Distinctive Features: Contains enzyme reverse transcriptase, integrating into a host cell chromosome.
  • Host: T-helper cells in the human immune system.

  Real World Connection: HIV is an example of a virus that has required extensive research and medical effort to manage.