MBIO 1010 - Lecture 14

• To be organic, you need a C and H
• 3 energy classes of microorganisms

  • metabolism
  • catabolism
  • anabolism
• metabolism

  • the sum total of all of the chemical reactions that occur in a cell
  • metabolism = catabolic reactions and anabolic reactions
• catabolic reactions (catabolism)

  • energy-releasing metabolic reactions (fermentation, respiration)
  • take something and you break it down
• Anabolic reactions (anabolism)

  • energy-requiring metabolic reactions (biosynthesis)
  • taking two things and putting them together - need energy to put them together
• microorganisms can be categorized according to

  • energy source
  • electron source
  • carbon source
• energy source

  • chemo
  • photo
• electron source

  • organo
  • litho
• carbon source

  • hetero
  • auto
• Chemo - obtain energy from chemical reactions
• photo - obtain energy from light
• organo - obtains electrons from reduced organic molecules (glucose, acetate)
• organo - obtains electrons from reduced organic molecules (glucose, acetate)
• litho - obtains electrons from reduced inorganic molecules (H2, H2S, Fe2+, NH4+)
• Heter obtains carbon from pre-existing organic molecules
• auto - obtains carbon from inorganic CO2
• microorganisms grouped into energy classes depending on their source of electrons and energy

  • chemoorganotrophs
  • chemolithotrophs
  • phototrophs
• chemorganotrophs - energy from chemical reactions involving organic material
• chemolithotrophs - energy from inorganic chemical reactions
• phototrophs - energy from light
• microorganisms grouped with respect to carbon source:

  • heterotrophs
  • autotrophs
• heterotrophs

  • use organic carbon for building cell carbon and biomass
• autotrophs

  • use CO2 to synthesize cell carbon
  • primary producers
• Classes of culture media: (3)

  • defined medium
  • minimal medium
  • complex medium
• Defined medium

  • exact chemical composition is known
  • useful for studying metabolism
  • doesn't use growth factors
• minimal medium

  • a defined medium that provides the minimum nutritional requirements for growth (no growth factors)
  • all minimal medium are defined mediums - not all defined mediums are minimal mediums
• complex medium

  • exact chemical composition is not known
  • often made from meat or yeast extracts (yeasts don't know exact chemical composition because all of them are different)
  • supply a variety of growth factors
  • t-soy broth and plates
  • peptone
  • has everything it needs to grow - don't know the exact chemical composition
• Yeasts are living cells - have all the things living cells need

  • nitrogen is accounted for
  • source of amino acids, purines, pyrimidines and many vitamins
  • amino acids serve as N source
  • can also serve as alternate source of carbon, energy and electron
  • allows growth of very fastidious organisms
• Nicotinic acid (NAD+) is a growth factor