Micro: Exam I Prep

CHAPTER 1 – History of Microbiology

Microbes / Pathogens / Basic Concepts

  • Microbes (uses): food production (yogurt, cheese), antibiotics, decomposition, biotechnology, nitrogen fixation.

  • Pathogen: a microorganism that causes disease.

  • Virulence: how strong or harmful a pathogen is.

  • Sign vs Symptom:

    • Sign: objective (fever, rash)

    • Symptom: subjective (pain, nausea)

Spontaneous Generation vs Biogenesis

  • Spontaneous generation: life arises from non-living matter (disproven).

  • Biogenesis: life comes from pre-existing life (correct theory).

Disproving spontaneous generation:

  • Francesco Redi: showed maggots come from flies, not meat.

  • Louis Pasteur: microbes come from air contamination, not spontaneous formation.

Key Scientists & Contributions

  • Aristotle: believed life could arise from non-living matter.

  • Robert Hooke: observed cork cells.

  • Antonie van Leeuwenhoek: discovered “animalcules.”

  • Carolus Linnaeus: developed classification system.

Taxonomy

  • Science of classifying organisms.

  • Three Domains:

    • Bacteria

    • Archaea

    • Eukarya

Other Key Figures

  • Robert Koch

    • linked specific microbes to diseases

  • Koch’s postulates:

    1. Microbe found in sick organism only

    2. Isolated and grown in pure culture

    3. Causes disease in healthy host

    4. Re-isolated from new host
      Limitations: viruses, ethical issues, asymptomatic carriers

  • Ignaz Semmelweis: reduced infections using handwashing

  • Florence Nightingale: improved hospital sanitation

Microbiota

  • Transient microbiota: temporary microbes (come and go)

  • Resident microbiota: permanent normal flora

Beneficial microbes

  • Digest food (gut bacteria)

  • Produce vitamins (K, B12)

  • Protect against pathogens

  • Used in fermentation and antibiotics

CHAPTER 2 – Microbial Chemistry

pH importance

  • Controls enzyme activity and growth

  • Extreme pH kills microbes

Molecules

  • Polar: charged, water-soluble

  • Non-polar: no charge, lipid-soluble

  • Hydrophilic: water-loving

  • Hydrophobic: water-fearing

Carbohydrates

  • Energy source + structure

Monosaccharides: glucose, fructose

  • quick energy

Disaccharides: glucose + glucose etc.

  • example: peptidoglycan building blocks

Polysaccharides:

  • glycogen (energy storage)

  • cellulose (plant structure)

  • chitin (fungi cell walls)

Penicillin

  • Targets bacterial peptidoglycan cell wall

  • Blocks cell wall synthesis → bacteria burst

Lipids

  • energy storage + membranes

Phospholipids:

  • form cell membranes

Saturated fats: rigid membranes
Unsaturated fats: fluid membranes

Mycolic acid

  • Found in acid-fast bacteria

  • Stain used: acid-fast stain

  • Cells appear red/pink

LPS (lipopolysaccharide)

  • Found in Gram-negative bacteria outer membrane

  • Causes strong immune response → fever, shock

CHAPTER 3 – Microbial Structure & Microscopy

Microbe morphology

  • Shapes:

    • coccus (round)

    • bacillus (rod)

    • spirillum (spiral)

  • Arrangements:

    • chains, clusters, pairs

Microscopy

  • Magnification = eyepiece × objective

  • Resolution = ability to distinguish detail

  • Contrast = difference between specimen and background

Gram Stain

  • Gram-positive: purple

    • thick peptidoglycan

    • retains crystal violet

  • Gram-negative: pink

    • thin peptidoglycan + outer membrane

    • loses crystal violet, takes safranin

Penicillin sensitivity

  • Gram +: more sensitive (no outer membrane)

  • Gram -: less sensitive (outer membrane protection)

Outer membrane advantages

  • Protection from antibiotics

  • Contains LPS

  • Porins allow selective entry of molecules

Acid-fast bacteria

  • Example: Mycobacterium tuberculosis

  • Hard to treat due to waxy mycolic acid layer

Mycoplasma

  • No cell wall

  • Causes pneumonia-like infections

Endospores

  • Dormant, highly resistant survival form

  • Example: Bacillus, Clostridium

Structures

  • Capsule: protection + immune evasion

  • Fimbriae: attachment

  • Pili: DNA transfer (conjugation)

  • Flagella: movement

  • Glycocalyx: sticky outer layer

  • Biofilms: microbial communities on surfaces

Pathogens

  • Opportunistic: only cause disease when immune system is weak

  • True pathogens: cause disease in healthy hosts

CHAPTER 4 – Eukaryotes & Parasites

Eukaryotes

  • Cells with nucleus + membrane-bound organelles

Endosymbiosis theory

  • Sequence:

    1. Host cell engulfed bacteria

    2. Bacteria became mitochondria

    3. Photosynthetic bacteria became chloroplasts

Evidence

  • Mitochondria/chloroplasts have own DNA

  • Double membranes

  • Divide independently

  • Similar to bacteria

Parasites & Vectors

  • Vector: organism that transmits disease (mosquito, tick)

Arthropods

  • Mosquitoes, ticks, fleas

Worms

  • Tapeworms: flat, intestinal parasites

  • Flukes: flatworms, blood/liver parasites

  • Roundworms: nematodes, intestinal infections