Lecture 9

• 3 domains of life

  • Bacteria
  • Archaea
  • Eukaryotes
  • all monophyletic
• Prokaryotes

  • Bacteria
  • Archaea
  • not monophyletic
• All monophyletic groups is a group that includes an ancestor of the group and all of its descendants but no others
• common ancestor of all life

  • hereditary information
  • amino acids
• Prokaryotes are diverse and interesting

  1. They represent two of the three domains of life
  2. The vast majority are single celled organisms
  3. They are the most abundant organisms on Earth
  4. They are essential for functioning of life as we know it
  5. They contribute to human illness, but also human health
• Archaea

  • separate domain
  • founded in 1970s by Carl Waese
  • difference in ribosomal DNA compared to other prokaryotes
• prokaryotes are single celled organisms

  • very few are multicellular
  • biofilms; rarely communicate with each other
• most abundant organisms on Earth

  • 1000 more species in humans
  • 700 prokaryotes on skin
  • human cells are less than the amount of prokaryotes in human
  • 39 trillion prokaryote cells on and in humans
  • 30 trillion human cells
• importance of prokaryotes

  • photosynthesis
  • soil
  • water
• prokaryotic illnesses

  • Cdiff
• Cdiff

  • clostridium difficiles
  • bacteria in digestive tract
  • affects microbiome
• microbiome is a community of species in body
• Ways to catalog prokaryotic diversity

  1. Enrichment culture
  2. DNA sequencing
  3. Shape
  4. Gram Stain
  5. Modes of Nutrition
• Enrichment culture

  • only a small portion of prokaryotes can be cultured
  • ineffective way to catalog bacterial species
• DNA sequencing

  1. Collect samples
  2. Generate small DNA fragments
  3. Assemble overlapping DNA sequences -- molecular phylogeny
• Shape

  • spherical = coccus
  • Rod-shaped = bacillus
  • treponema pallidum - causes syphilis (STD)
  • Corkscrew = idum
• Gram Stain

  • dye, iodine
  • Gram-positive: peptidoglycan take in dye (purple)
  • Gram-negative: outer membrane + peptidoglycan + plasma membrane -- makes it harder for penicillin to reach it
• Modes of nutrition

  • autotrophs
  • photoautotrophs
  • chemoautotrophs
• autotrophs do not need organic compounds as a source of food and energy
• chemoautotrophs obtain energy by oxidization of electron donors in their environment
• photoautotrophs

  • use photosynthesis to synthesize organic compounds using energy from light
  • photosynthesis: intakes light energy makes glucose and results in amino acids, DNA, phospholipids, and more organic compounds
• photosynthesis reaction

  6CO2 + 12H2O + light --> C6H12O6 + O2 +6H2O
• Chemical reaction

  6H2S +2O2 --> SO4 +2H + energy
• Bacteria has peptidoglycan in cell wall or outside
• Prochlorococcus and Synechococcus

  • marine bacteria
  • do photosynthesis: able to fight green house gas pollution
  • most abundant photosynthetic organisms on Earth
• Penicillin

  • peptidoglycan: hard cell wall to protect cell membrane
  • goes through peptidoglycan
  • Streptococcus: chain of cells
  • Staphylococcus: bunch of cells
• Gram-positive

  • streptococcus pyogenes: strep throat; scarlet fever
  • streptococcus pneumoniae: bacterial pneumonia
  • staphylococcus aureus: skin infections, toxic-shock syndrome
• Gram-negative

  • Salmonella enterica: food poisoning
  • Neisseria gonorrhea: gonorrhea
• Gonorrhea

  • second most common infectious disease in the U.S.
  • 50% of cases for 19-24 year-olds
  • more susceptibility for women, often asymptomatic
  • growing antibiotic resistance
• (5) Photosynthesis

  1. Process is complex
  2. Photoautotrophs use glucose as the raw material to make other organic compounds needed for life
  3. Byproduct is free oxygen
  4. We don't know how it evolved
  5. Most life is dependent on it