Microbiology Study Notes

Intro to Microbiology

• Microbiology is the study of microbes, which are tiny organisms too small to see with the naked eye.
• Microbes include bacteria, viruses, fungi, algae, and protozoa.
• Microbiology is important for:
  • Understanding disease mechanisms and treatments.
  • Decomposition of waste and nutrient recycling.
  • Oxygen production.
  • Food production (yogurt, bread, cheese).
  • Medicine (antibiotics, vaccines).
  • Environmental cleanup (oil spills, pollutants).

Classification & Taxonomy

• Taxonomy is the science of naming and organizing living things.
• It helps determine the relationships between organisms.
• Living things are grouped into taxa.
• There are 8 main taxonomic levels:
  • Domain
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Mnemonic device: "Divine King Phillip Came Over For Great Spaghetti."
• Domain is the broadest category.
• Species is the most specific category.
• Scientific names use genus and species (e.g., Homo sapiens for humans), created by Carl Linnaeus.
• Genus is capitalized, and species is lowercase; both are underlined or italicized.

Bacteria Basics

• Bacteria are living organisms.
• Two main types:
  • Archaebacteria: ancient, live in extreme conditions.
  • Eubacteria: common, found in everyday places.
• Bacteria are prokaryotic (no nucleus).
• Five categories of bacteria:
  • Gram-positive: thick cell walls, stain positive.
  • Cyanobacteria: blue-green bacteria, perform photosynthesis, produce oxygen.
  • Chlamydias: live inside other cells, often cause disease.
  • Spirochetes: spiral-shaped, help cows digest food, can cause Lyme disease or syphilis.
  • Proteobacteria: live in our gut, help us, some cause ulcers.
• Bacterial shapes:
  • Spheres (coccus)
  • Rods (bacillus)
  • Spirals (spirillum)
• Arrangements: chains or clusters.

How Bacteria Reproduce

• Two main methods of reproduction:
  • Binary fission: asexual, one cell splits into two identical cells; fast, doesn't need another bacterium.
  • Conjugation: sexual, two bacteria connect and exchange a plasmid (DNA piece).
• Conjugation helps bacteria gain new traits like antibiotic resistance.
• A plasmid is a small, extra DNA loop separate from the main chromosome.
• Plasmids carry helpful genes, like antibiotic resistance genes.
• Antibiotic resistance makes infections harder to treat.

Growing Bacteria in a Lab

• Agar (jelly-like substance) is used in a petri dish.
• Everything is sterilized to prevent contamination.
• Bacteria are added using a streak plate method.
• Incubation at approximately 37°C (body temperature).
• Colonies (groups of the same bacteria) form after a day or two.

Viruses - What They Are

• Viruses are non-living particles.
• They cannot breathe, eat, grow, divide, or produce waste.
• A virus consists of genetic material (DNA or RNA) inside a protein shell (capsid).
• Viruses cannot reproduce on their own; they must infect a living cell.
• DNA viruses are stable and don't change much.
• RNA viruses are unstable and mutate easily; hence the need for a new flu shot every year.
• Viruses infect specific cells (host range).
  • Example: rabies virus has a large host range, cold virus has a small host range.

How Viruses Reproduce (Replication)

• Viruses reproduce by hijacking a host cell.
• Two main replication cycles:
  • Lytic Cycle:
    • Virus attaches to a cell and injects its DNA or RNA.
    • Virus takes over the cell, makes copies of itself.
    • The cell bursts open, releasing new viruses.
    • This process is fast and kills the cell.
  • Lysogenic Cycle:
    • Virus injects its DNA into the cell, but it hides in the cell's DNA.
    • The cell copies itself, and the viral DNA stays hidden.
    • Stress or temperature change can activate the virus, initiating the lytic cycle.

Vaccines and Immunity

• A vaccine is a dead or weak form of a virus.
• Vaccines stimulate the body to create antibodies.
• Antibodies mark the virus for destruction by white blood cells.
• RNA viruses mutate, requiring frequent new vaccines.
• DNA viruses don't change much, so one vaccine can provide lifetime protection.

Host vs Vector

• A host is the organism infected by the virus.
• A vector is an organism (e.g., mosquito) that carries and spreads the virus without getting sick itself.

Epidemics vs Pandemics

• An epidemic is a rapid disease spread in one area (city or town).
• A pandemic is a worldwide disease spread.

Dichotomous Keys

• A dichotomous key is a tool to identify organisms.
• It presents two choices at each step.
• Based on traits (e.g., number of eyes, presence of spikes), choices lead to the organism's identification.
• Analogous to a flowchart leading to the answer.