Characteristics of Prokaryotes:

  • Small size and rapid reproduction
  • High genetic variation → live in diverse environments                                                                   

Bacteria Structure and Review

  • Cell wall: made with peptidoglycan (carb polymer with amino acid)
    • Function: protects cell, stops from bursting in hypotonic solution, structure determines rate of transformation
    • Structure either gram positive and negative
      • (+) = simple
  • (-) = more complex, less peptidoglycan
  • Capsule: layer of polysaccharides and proteins that surround cell wall
    • Protect against dehydration, cell adherence, resist host organism defenses
  • Endospores: resistant cells
  • Plasmids: small, circular independently replicating (circular) DNA molecules
    • Can be exchanged with other bacteria introducing genetic variation and promoting the transfer of antibiotic or pathogenic genes to harmless strains
  • Quorum sensing: some bacteria release signalling molecule that recruits other bacteria → evaluate the local density of bacteria → bacteria respond and aggregate → form biofilms
  • Biofilms: dense populations of bacteria linked by adhesive proteins
    • Adhesive proteins help bacteria attach to substrates

Groups of Bacteria

  • Can be categorized by how they obtain energy and carbon (include 4 modes)
  1. Cyanobacteria: photosynthetic
  2. Purple sulfur bacteria: photosynthetic but split H₂S (instead of water) to get electrons
  3. Nitrogen-fixing bacteria: convert/fix N2 to ammonia (NH₃) → used to make nitrogen-containing amino acids and nucleotides
  • Some have mutualistic relationships with plants and bacteria
  1. Heterotrophic bacteria: obtain carbon and energy from organic molecules
  • Ex: parasites, pathogens, decomposers, and bacteria in the digestive tract that also compete with pathogenic bacteria


  • Use flagella
    • Pro and eu. flagella have diff proteins, molecular composition, and method

Reproduction: Binary Fission

  • Asexual→ no genetic variation
  • Rapid reproduction + no proofreading enzymes → high rate of mutation = main method of creating variation for evolution (fast)


  • Obligate aerobes require O2; obligate anaerobes are poisoned by O2; Facultative anaerobes can survive with or without             

Some antibiotics disable the activity of bacterial ribosomes or break down cell wall