Pathogens and Bacterial Growth Basics

Pathogens: Basics

• Pathogens are microbes that cause disease. Not all microbes are pathogens. Bacteria, viruses, and fungi are types of pathogens.
• Diseases can also arise from non-pathogenic causes, like diabetes (pancreas issues).
• Bacteria are microscopic single-celled organisms found everywhere (environment, living organisms). Not all bacteria are harmful. Some cause diseases like pneumonia and tuberculosis.
• Bacterial cells lack a true nucleus (only a loop of DNA) and certain cellular structures like mitochondria but may have additional DNA loops (plasmids).

Bacterial Growth

• Bacterial growth follows a pattern:
  • Lag phase: Slow growth as cells adjust.
  • Log phase: Rapid doubling of the bacterial population (optimal conditions).
  • Stationary phase: Cell production and death rates equalize.
  • Death phase: Cell death exceeds production.
• Bacteria can survive harsh conditions as spores, a dormant state allowing re-growth in favorable conditions.
• Bacteria come in three main shapes: Bacillus (rod-shaped), Coccus (spherical), Spirillum (spiral).

Fungi

• Some fungi are pathogens causing diseases like athlete's foot and ringworm.
• Fungi are not plants; they lack chlorophyll.
• Fungi have a body (mycelium) consisting of branching filaments called hyphae.
• The hyphae secrete enzymes to digest food outside the fungus, then absorb digested nutrients.
• Fungi reproduce by spores, which can spread infection.
• The spread of fungal diseases increase with poor hygiene.

Viruses

• Viruses are parasitic pathogens relying on host cells for reproduction.
• Viruses are much smaller than bacteria or fungi, needing an electron microscope to be seen.
• Virus structure includes a core of DNA or RNA surrounded by a protein coat. They lack a nucleus and a cell membrane.
• Viruses reproduce by: entering a host cell, hijacking the cell's functions, replicating viral components, assembling new viruses, and causing the host cell to burst, releasing new viruses to infect other cells.

Effects of Pathogens

• Pathogens must enter the body to cause harm. Entry points include the nose, mouth, and skin cuts.
• Pathogens multiply rapidly within the body, leading to illness. Incubation period is the initial stage of disease before symptoms appear.
• Pathogens cause disease by either destroying tissue (e.g., tuberculosis) or producing toxins (e.g., food poisoning).
• Diseases spread when pathogens are transmitted from one person to another. An infectious person is a carrier of the disease.

Signs vs. Symptoms

• Symptoms are subjective experiences like pain, fatigue, dizziness.
• Signs are objective observations by clinicians, such as fever, rash, or high blood pressure.

Key Terms

• Microbes: microscopic organisms.
• Pathogens: disease-causing microbes.
• Bacteria: single-celled microbes lacking a nucleus.
• Viruses: parasites needing host cells to reproduce.
• Fungi: non-plant organisms with a mycelium comprised of hyphae.

This quiz covers the basics of pathogens, including the different types such as bacteria, viruses, and fungi. It also explores bacterial growth phases and how environmental conditions affect bacteria. Test your understanding of these crucial microbiology concepts.