Lecture Notes: Bacteria - Definition, Types, Benefits, Risks, and Examples

Introduction to Bacteria

• Definition:
  • Microscopic, single-celled organisms (singular: bacterium).
  • Found globally, including on/in human body (skin, airways, mouth, digestive/reproductive/urinary systems).
  • Outnumber human cells 10 to 1.

Benefits of Bacteria

• Non-Harmful Bacteria:
  • Most aren't harmful.
  • Some are beneficial, known as resident flora or microbiome.
    • Role: Absorb nutrients, break down food, prevent harmful bacteria growth.

Risks of Bacteria

• Pathogenic Bacteria:
  • Can cause diseases by reproducing quickly and releasing toxins.
  • Examples:
    • Streptococcus (strep throat)
    • Staphylococcus (staph infections)
    • Escherichia coli (E. coli infections)
  • Can lead to conditions like septicemia and sepsis.
• Other Pathogenic Examples:
  • Aerococcus urinae (urinary tract infections)
  • Chlamydia trachomatis (chlamydia)
  • Bordetella pertussis (whooping cough)

Treatment of Bacterial Infections

• Antibiotics:
  • Effective against most bacterial infections.
  • Overuse can lead to antibiotic resistance.
  • Importance of completing prescribed antibiotic courses.

Classification of Bacteria

Scientific Naming

• Based on genus and species characteristics, e.g., Clostridium botulinum (causes botulism).

Shapes

• Cocci: Spheres or ball-shaped.
• Bacilli: Rod-shaped.
• Spirochetes: Spirals or helixes.

Oxygen Requirements

• Aerobes: Need oxygen.
• Anaerobes: Cannot live with oxygen.
• Facultative: Can survive with or without oxygen.

Genetic Makeup

• Each bacterium has distinct genotypes.

Staining

• Gram Staining:
  • Gram-Positive: Blue to purple (e.g., Corynebacterium, Clostridium, Listeria).
  • Gram-Negative: Red to pink (e.g., Pseudomonas, Proteus, Klebsiella).
  • Different responses to antibiotics.

Bacteria vs. Viruses

• Differences:
  • Bacteria: Affected by antibiotics.
  • Viruses: Not affected by antibiotics, may need antivirals.

Antibiotic Resistance

• Challenge: Overuse leads to resistant strains (e.g., MRSA).
• Mechanism: Antibiotics destroy bacterial cell walls or DNA.

Bacterial Reproduction

• Binary Fission:
  • Bacteria duplicate DNA and split into two.

Bacterial Classification

• Prokaryotic Nature:
  • No nucleus, simple structure with cell walls, cytoplasm, ribosomes, and DNA.
  • Use flagella for movement.

Plastic-Eating Bacteria

• Discovery (2016):
  • Ideonella sakaiensis consumes polyethylene terephthalate (PET) plastic.
  • Potential role in reducing plastic pollution.

Conclusion

• Vast diversity of bacteria, most are harmless or beneficial.
• Pathogens require treatment (antibiotics).
• Importance of proper antibiotic usage to prevent resistance.