Prokaryotic and Eukaryotic Pathogens

Introduction

• Phylogenetic Tree (Phylogeny)
  • Shows relatedness between different species.
  • Illustrates evolution from a common ancestor.

Prokaryotic Pathogens

Bacterial Diversity

• Majority evolved to become pathogenic via horizontal gene transfer (plasmids, transposons).

Major Phyla Impacting Human Health

1. Firmicutes

   • Gram-positive; thick peptidoglycan cell wall.
   • Includes endospore producers like Clostridium, Bacillus.
   • Non-sporeformers include Enterococcus, Staphylococcus.

2. Actinobacteria

   • High GC content; beneficial (Streptomyces - antibiotics).
   • Corynebacterium diphtheriae, Mycobacterium tuberculosis, leprosy.

3. Proteobacteria

   • Diverse metabolism; Gram-negative.
   • Includes Escherichia coli, Salmonella, Klebsiella (nosocomial pneumonia).

4. Bacteroidetes

   • Gram-negative, rod-shaped obligate anaerobes.
   • Part of normal intestinal microbiota; can be opportunistic.

5. Spirochetes

   • Coiled shape, includes pathogens like Borrelia burgdorferi (Lyme disease).

6. Cyanobacteria

   • Photosynthetic; nitrogen fixation.
   • Beneficial, non-pathogenic.

7. Chlamydiae

   • Obligate intracellular parasites; lack cell wall.
   • Includes STI chlamydia; can cause eye infections, pneumonia.

Bacterial Evolutionary Incubators

• Zoonotic Hosts: Pathogens evolve in animals, can transmit to humans.
• Shelter Species: Bacteria evolve within organisms like nematodes.
• Natural Environment: Gene transfer in soil, water.

Detailed Phyla Examination

Firmicutes and Actinobacteria

• GC Content:
  • Firmicutes: Low GC
  • Actinobacteria: High GC
  • Mycolic Acids: Present in Actinobacteria cell wall.

Examples of Pathogenic Bacteria

• Endospore Formers: Bacillus anthracis, Clostridium difficile.
• Non-Sporeformers: Lactobacillus, Listeria (cold temperature growth).

Gram-Negative Bacteria

• Proteobacteria: Enterobacteria family, Pseudomonas aeruginosa (opportunistic).
• Bacteroidetes: Part of normal microbiota, breakdown toxins.

Eukaryotic Pathogens

Differences from Prokaryotes

• Eukaryotic cells have a nucleus, linear chromosomes, organelles.

Fungi

• Unicellular (Yeasts): Reproduce sexually/asexually.
• Filamentous Fungi: Have hyphae, mycelium.

Protozoa

• Amoebas: Move via pseudopods (Entamoeba histolytica).
• Ciliates: Use cilia for movement.
• Apicomplexans: Include Plasmodium (malaria).
• Flagellated Parasites: Giardia.

Helminths

• Nematodes (Roundworms): Enterobius vermicularis (pinworm).
• Trematodes (Flukes): Flatworms, no outlet for waste.
• Cestodes (Tapeworms): Segmented, in uncooked meat.

Arthropods

• Mites, Ticks: Sarcoptes scabiei (scabies), vector for Borrelia (Lyme disease).
• Ectoparasites: Lice, do not enter host body.

This concludes the discussion on prokaryotic and eukaryotic pathogens.