Pathogens

Pathogens are microorganisms that can cause disease within a host.

Types of Pathogens

  • Bacteria: Single-celled organisms that can either be beneficial or pathogenic to humans.

  • Viruses: Acellular entities that require a host to replicate and may cause diseases ranging from the common cold to HIV/AIDS.

  • Fungi: Includes yeasts and molds. Some fungi are pathogenic to humans.

  • Protozoa: Single-celled eukaryotes, often parasitic, and can cause diseases such as malaria.

  • Prions: Infectious agents composed entirely of a protein material that can fold in multiple, structurally abstract ways. They can cause several neurodegenerative diseases in humans such as Creutzfeldt-Jakob disease (CJD).

Micron Measurements and Comparative Sizes

A micron is a unit of measurement for microorganisms; human hair is approximately 70 microns.

  • Micron: A micron is a length equal to 1/25,400 of an inch or 1/1,000 of a millimeter.

  • Bacteria: Bacterial sizes vary, but they generally range from 0.2 to 10 microns in length.

  • Viruses: Viruses are much smaller than bacteria, often ranging from 0.02 to 0.3 microns. They are so small that they can only be seen with an electron microscope.

Aerobic vs. Anaerobic Organisms

  • Aerobic Organisms: These organisms require oxygen to survive

  • Anaerobic Organisms: These organisms do not require oxygen and may even be killed by it. 

Endospores (Spores)

- Endospores are a type of dormant cell produced by certain bacteria.

- Are highly resistant to environmental stresses like heat, UV radiation, and disinfectants. For that reason, live spores are used as a monitoring device for sterilizers in the form of a BI (Biological Control).

Gram Staining

Gram staining is a method to classify bacteria based on the properties of their cell walls.

Outcomes:

  • Gram-Positive: Stain purple/blue; bacteria with thick peptidoglycan cell walls.

  • Gram-Negative: Stain pink/red; bacteria with thin peptidoglycan cell walls.

Binary Fission

Binary fission is a form of asexual reproduction where a single organism divides into two parts after replicating its genetic material.

Cells:

The basic living units of life, with the human body consisting of over 100 trillion cells.

Basic Cell Anatomy

  • Cell Membrane: A lipid bilayer regulating substance entry and exit.

  • Cytoplasm: A gel-like substance; the inside of a cell, where cell activities happen.

  • Nucleus: The DNA-containing control center for cell growth and reproduction.

Bacterial Shapes

  • Cocci: Spherical or oval shape.

    • (Tip: “Cocci” has a lot of C’s; “C” looks circular) 

  • Bacilli: Rod or cylinder shape.

    • (Tip: “Bacilli” has a lot of L’s; “l” looks like a cylinder/Rod) 

  • Spirilla: Spiral-shaped.

    • (Tip: “Spirilla” think of spiral)