Prokaryotes: Eubacteria and Archaea

• Prokaryotes


  Eubacteria and Archaea
• Bacteria are responsible for many diseases like cholera, leprosy, typhoid fever, strep throat, tuberculosis, salmonella poisoning, lyme disease… and MANY others
• Pathogens


  Bacteria that can infect and cause disease
• Bacteria


  • Can infect livestock and threaten our food sources
  • Can be decomposers - helping with the carbon cycle
  • Can be photosynthetic and make oxygen (ex. cyanobacteria)
  • Can help us make vitamins in our guts (like B12)
• Bacteria have lived on earth for over 3.5 billion years!
• Domain


  A top level classification of life, above kingdom
• Prokaryotes diversified into 12 distinct groups of surprising diversity in energy requirements, ecological roles and importance to humans
• Characteristics of bacteria


  • All are single-celled
  • All are prokaryotes - DNA is not surrounded by a membrane
  • Cell organelles are NOT surrounded by a membrane
  • DNA of bacteria is made up of a single chromosome
  • All bacteria reproduce asexually by binary fission
• Structure of bacteria


  • Chromosome in a single loop of DNA called a NUCLEOID
  • Ribosomes (used in protein synthesis) are scattered throughout cytoplasm
  • Often have Flagella for movement
  • Often have pili (hair-like structures) to interact with other bacteria
  • Bacteria often carry other DNA in addition to the nucleoid - this is on a circular piece of DNA called a PLASMID
  • Cell walls are thick, strong and rigid and are made of peptidoglycan
  • Often surrounded by a sticky CAPSULE to reduce water loss, resists high temperatures and help keep out antibiotics and viruses
• Bacteria Shapes


  • Normal - Skin micrococcus
  • Strep throat streptococci
• Gram Stain


  A way to classify bacteria based on their reaction to a dye
• Gram Stain Results


  • Gram-positive: Cells that retain the dye and appear purple
  • Gram-negative: Cells that don't retain dye and are light pink
• Gram-positive bacteria


  • Cells have different cell wall
  • Are more common, less pathogenic
• Autotrophic


  Using sunlight for energy
• Heterotrophic


  Living off of other living things
• Respiration Types


  • Aerobes (use oxygen for respiration)
  • Anaerobes (do not need oxygen for respiration)
• Obligate aerobes


  • Need oxygen to survive
• Obligate anaerobes


  • Presence of oxygen kills them
• Facultative anaerobes


  • Can survive with or without oxygen
• Reproduction in Bacteria


  1. Asexually by binary fission

  2. Sexually by Conjugation
• Binary fission


  Parent cell divides into two identical offspring
• Conjugation


  Two bacteria cells connect via a protein bridge and the plasmid of one cell is given to the other
• Endospores


  Highly resistant structure that forms around the chromosome when a cell is under stress
• Eubacteria Groups


  • Proteobacteria
  • Green bacteria
  • Cyanobacteria
  • Gram negative - disease causing
  • Spirochetes
  • Chlammydias
• Eubacteria


  • Important for: nitrogen fixation and decomposition (carbon/oxygen cycle)
  • Only a small percentage are pathogenic (disease causing) produce toxins: Endotoxins - released when certain gram-negative bacteria split (seldom fatal, cause vomiting, fever), Exotoxins - released by multiplying bacteria (often toxic, often fatal)
• Archaebacteria


  • Oldest group of organisms
  • Live in extremely diverse environments
  • Cell wall and membrane are different from eubacteria, and more than half of the genes are different as well
  • Unique cell walls and membranes that lack peptidoglycan and are VERY resistant to damage from extremes like temperature
  • Use binary fission for reproduction like eubacteria
• Types of Archaea and their Habitats

  • Methanogens: Live in swamps, sewage, digestive tracts
  • Halophiles = salt lovers! Live in the dead sea
  • Thermophiles = heat lovers! Live in hot springs, hydrothermal vents ocean floor
  • Psychrophiles = cold lovers! Live at the poles (ice) and cold ocean depths
• Methanogens


  • Convert chemical compounds into methane to get energy
• Halophiles


  • Can use food or sun for energy
• Thermophiles


  • Thrive in temperatures ranging from 75℃ to 95℃
• Psychrophiles


  • Thrive in temperatures ranging from -10℃ to -20℃
• Helpful uses of Bacteria

  • Waste Management
  • Sewage treatment
  • Dairy foods
  • Our digestion!
• Antibiotic


  Medicine that treats or prevents bacterial infections by inhibiting the growth of or destroying bacteria
• Antibiotic Resistance


  When bacteria develop the ability to defeat the drugs designed to kill them
• Antibiotic resistance is not the body becoming resistant to the antibiotics - it is the bacteria
• Antibiotic resistance is more likely to happen when antibiotics are being used unnecessarily or misused
• How antibiotic resistance develops

  Mutations in DNA, acquisitions of resistance genes