Lecture Notes on Bacteriophages

Introduction

• War between bacteriophages and bacteria has been ongoing for billions of years.
• Bacteriophages, or 'phages', are the deadliest entities on Earth.

What are Bacteriophages?

• Phages are viruses that are not considered fully alive or dead.
• Structure:
  • Head: Icosahedron shape (20 faces, 30 edges).
  • Tail: Long with leg-like fibers.
• Abundance: More phages on Earth than all other organisms combined, including bacteria.
• Presence: Billions of phages are found everywhere, including on human bodies.

Impact on Bacteria

• Phages are responsible for a large number of bacterial deaths daily.
• Up to 40% of ocean bacteria are killed by phages every day.
• Phages are specialized and require a host to survive and reproduce.
  • They target specific bacteria and their close relatives.

Mechanism of Action

1. Phage attaches to a bacterium via tail fibers.
2. It injects its genetic material into the bacterium.
3. Bacterium is hijacked to produce new phages.
4. The bacterium eventually bursts, releasing new phages.

Antibiotics and Bacteria

• Historical context:
  • Discovery of antibiotics about 100 years ago revolutionized medicine.
  • Antibiotics became overused, leading to the development of 'superbugs'.
• Superbugs are bacteria resistant to multiple antibiotics, posing a significant health risk.
  • In the US, over 23,000 deaths annually due to resistant bacteria.

Phages as a Solution

• Phages could be injected into the body to treat bacterial infections.
• Phages are specialized and do not harm human cells; humans are immune to them.
• Phages act like guided missiles targeting specific bacteria without affecting the good bacteria.

Resistance and Evolution

• Bacteria have evolved defenses against phages, but phages are also evolving.
• There is a potential catch-22: bacteria may have to sacrifice antibiotic resistance to develop phage resistance.

Case Study

• Example of successful phage treatment:
  • Patient with Pseudomonas Aeruginosa infection treated with phages and antibiotics.
  • Infection cleared after treatment.

Current Status and Future

• Phage therapy is still experimental, with limited pharmaceutical investment.
• Increased attention on phages; the largest clinical trial began in 2016.
• The era of antibiotic dominance is nearing its end, making phages a promising alternative.

Conclusion

• Injecting phages into the human body could potentially save millions of lives.
• This discussion supported by the Bill & Melinda Gates Foundation.