Microbes and Zoonotic Diseases

• Microbes represent the vast majority of species diversity.
• They are used to manipulate processes in countless ways.
• Microbes are the oldest life forms on Earth.
• They constitute a major portion of Earth's biomass.
• Microbes can be harmful by causing food spoilage, corroding infrastructure, and damaging art through biofilms.

Zoonotic Diseases

• Zoonotic diseases transmit from animals to humans, rather than from human to human.
• Examples include rabies, Lyme disease, salmonellosis, COVID-19, and bird flu.

Relative Burden of Infectious Microbes

• In the 1900s, there were fewer non-microbial diseases (e.g., less cancer and strokes, more flu).
• Currently, there are more non-microbial deaths (e.g., less flu, more strokes and cancer).
• Developing countries experience more microbial deaths.
• Non-developing countries experience more non-microbial deaths.

Examples of Microbes

• Fungi
• Bacteria
• Helminths
• Viruses
• Yeast
• Archaea
• Protists

Ways Microbes Are Manipulated for Human Use

• Agriculture
• Energy generation
• Cures
• Fermented foods
• Microbiomes
• Environmental cleanup

Prokaryotic Cells vs. Eukaryotic Cells

Prokaryotic:

• Copies DNA in preparation for cell growth.
• Has a cell membrane.
• Does not contain a nucleus.
• Contains cytoplasm (cytosol = bodily fluids).
• Lacks mitochondria.
• Contains DNA and RNA polymerase, and ribosomes (ribosomes speed reactions and build proteins).
• Lacks chloroplasts.
• Has a genome consisting of DNA.
• Contains at least one chromosome (DNA with proteins).
• Includes bacteria and archaea.
• Performs transcription and translation (translation builds proteins).

Eukaryotic:

• Contains a nucleus.
• Produces DNA and RNA polymerase and ribosomes.
• Contains mitochondria.
• Has chloroplasts.
• Plants, animals, protozoa, and fungi are eukaryotic.
• Contains endoplasmic reticulum and Golgi apparatus.

Both:

• Have Cell membrane
• Contains cytoplasm consisting of cytosol
• Has genome consisting of DNA
• Contains at least one chromosome

Binomial Nomenclature

• The first name is always the genus (noun), e.g., Staphylococcus.
• The second name is always the species (adjective), e.g., aureus.
• Underline or italicize the entire name.
• Example: Staphylococcus aureus or Staphylococcus aureus.
• Subsequent mentions can be abbreviated: S. aureus or S. aureus.

Taxonomic Hierarchy

• Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
• Mnemonic: Dear King Phillip Came Over For Good Soup

Kingdoms in Domains

• There are no kingdoms in the Bacteria or Archaea domains.

Strain Definition

• A strain is a variant of a virus, bacterium, or fungus.

Strain Placement

• The term 'strain' fits within species in the taxonomic hierarchy.

Microbial Groups

Bacteria/Archaea:

• Single-celled organisms with cell walls made of peptidoglycan (except Archaea, which lack peptidoglycan).
• Can be pathogenic (Archaea are generally not).
• Found in various environments.
• Taxonomic Group: Domain
• Cell Type: Prokaryotic

Fungi (Yeast and Mold):

• Yeast are single-celled and reproduce by budding or fission.
• Mold are multicellular, composed of thread-like structures, and reproduce by spores.
• Taxonomic Group: Kingdom
• Cell Type: Eukaryotic

Protists:

• Diverse group, mostly single-celled.
• Can be plant-like, animal-like, or fungus-like.
• Taxonomic Group: Kingdom
• Cell Type: Eukaryotic

Algae:

• Photosynthetic organisms that can be single-celled or multicellular.
• Found in water or damp areas.
• Taxonomic Group: Kingdom Protistae or Plantae
• Cell Type: Eukaryotic

Helminths:

• Multicellular parasitic worms.
• Taxonomic Group: Kingdom Animalia
• Cell Type: Eukaryotic

Viruses:

• Acellular entities consisting of DNA or RNA within a protein coat.

• Requires a host cell to replicate.

• Can affect all forms of life.

• Taxonomic Group: Not Classified

• Cell Type: Acellular

• Cells lacking a nucleus are prokaryotic.

• Entities that are not cells or require a host are acellular.

The 5 I's of Microbiology

• Inoculation: Introduction of a sample into a container of media.
• Incubation: Providing cells with optimal conditions for growth in media.
• Isolation: Separating one species from another.
• Inspection: Observing cultures to ensure purity after isolation.
• Identification: Determining the species and strain of the microbe.
• Growth in media is called cultures.
• Colonies are billions of cells piled on top of each other, visible to the naked eye.
• Sterile means free of all life forms and endospores.

Physical States of Media

• Liquid: Suitable for growing large amounts of microbes.
• Solid: Useful for isolating and purifying single colonies of microbes.
• Semisolid: Ideal for assessing microbial motility and anaerobic growth.

Selective vs. Differential Media

• Selective Media: Intended to grow only certain types of microbes (e.g., adding acid to select for acid-loving microbes).
• Differential Media: Tests for specific microbial traits, indicated by color changes for positive or negative results (e.g., different colors for Gram-positive and Gram-negative bacteria).

Defined vs. Undefined Media

• Defined Media: Contains precisely known quantities of all ingredients (e.g., 1 g/L glucose).
• Undefined/Complex Media: Contains ingredients of unknown composition or concentration, derived from natural sources (e.g., peptone, yeast extract, agar).

Staining Techniques

• Simple Stain: Uses one basic/positive (blue, violet) stain.
  • Stains the microbes, leaving the background white.
  • Requires staining.
• Differential Stain: Uses more than one stain to differentiate between bacterial groups.
  • Example: Gram stain (purple = Gram-positive, pink = Gram-negative).
  • Requires staining.
• Negative Stain: Uses an acidic stain (negative ion).
  • Stains the background, leaving microbes clear.
  • Useful for observing shapes and sizes.
  • Does not require staining.

Brightfield Microscopy

• Uses visible light to illuminate samples.
• White background.
• Requires fixing and staining to see microbes.
• Resolving power of 25 μm.
• Uses glass lenses.
• Uses radiation light.

Microbes are the oldest life forms and represent the vast majority of species diversity. Zoonotic diseases transmit from animals to humans, examples include rabies, Lyme disease, salmonellosis, COVID-19, and bird flu. Developing countries experience more microbial deaths.