MBIO 1010 - Lecture 13

• Macronutrients are elements required in large amounts to build macromolecules which are the building blocks of cell material

  there are 10 macronutrients

  • C HOPKNS CaFe Mg

  CHONPS (the big 6) makeup >90% of the dry weight of the cell
• 4 different macromolecules

  • lipids
  • carbs
  • proteins
  • nucleic acids
• Protein

  • CHON and S
  • polymer made of building blocks - amino acids
  • >50 % of cells dry weight
  • sulfur for mRNA
• Lipids

  • CHOP
  • phosphate in phospholipids
  • building blocks = fatty acids and glycerol (backbone)
• Carbohydrates

  • CHON
  • Building blocks = sugar
  • Ex of when nitrogen is added is in - polysaccharides and peptidoglycan (NAG)
• Nucleic acids

  • CHONP
  • building blocks = nucleotides
  • EX. DNA and RNA
  • Nucleotides are ATCG
  • nucleotides are not elements
• Se is not a macronutrient
• Other macronutrients - inorganic ions (K, Mg, Ca, Fe)

  • often serve as metabolic co-factors
  • non-protein component required for enzyme function
  • enzymes involved in protein synthesis require K+
  • cytochromes (electron carrier) requires Fe2+
• Mg2+ helps stabilize membranes and nucleic acids
• Ca2+ helps stabilize cell walls, and plays a role in heat stability of endospores
• all 10 of the macronutrients should be considered when making media
• Sequester is when you find it and take it for yourself
• we don't always need to add calcium to media because they are not 100% pure and so we are not overly worried about them because bacteria can sequester it for themselves
• Micronutrients

  • elements required in very small amounts (trace elements)
  • serve as cofactors for enzymes
  • Se is required to make the unusual amino acid selenocysteine
  • essential but don't need to add it because they can get it on their own
  • typically dont add it because they can find it in their environment and sometimes we put it in the media which is important for studying metabolism
• Growth factors

  • small organic molecules required for growth
  • if an organism cannot synthesize the growth factor, then it must be added to medium to grow that microbe in the lab
• there are three classes of growth factors:

  • amino acids
  • purines and pyrimidines
  • vitamins
• amino acids

  • 20 amino acids are needed for protein synthesis
• purines and pyrimidines

  • A, G, T, C and U
  • Needed to make nucleotides, building blocks of DNA and RNA
  • UCT are the pyrimidines (single ring)
  • AG are the purines (double ring)
• Vitamins

  • small molecules used to make organic cofactors
  • non-protein components required by some enzymes
  • Ex. Nicotinic acid -> NAD+
• Growth factor requirements

  • many have no growth factor requirements such as E.coli
  • addition of growth factors to medium may promote growth
  • some bacteria require many such as Leuconostoc mesenteroides requires all 20 amino acids, 4 purines and pyrimidines, 10 different viramins
• Nutrient sources usually identified by element

  • H,O
  • No specific nutrient
  • found in H2O and organic components
• Nutrient sources usually identified by element

  • P
  • usually provided as phosphate salt (PO4^3-)
  • Ex. K2HPO4, KH2PO4
  • Reason: usually acquired as PO4^3- in the environment
  • in freshwater systems PO4^3- is often limiting
• Limiting nutrients

  • would never be hydrogen or oxygen
  • limiting nutrients and essential nutrients are not the same thing
  • In relatively low concentration compared to other nutrients
  • when it runs out, growth stops despite other nutrients present
• Nutrient sources usually identified by element

  • N (many possible sources)
  • Inorganic N
  • Provided as salts (KNO3 or NH4Cl)
  • must be reduced to NH3 - used to make amino acids (NH2)
  • Organic N
  • provided as N rich organic molecules (ex. amino acids or short peptides) - does not need to be reduced
  • Atmospheric N2
  • N2 is reduced to 2NH3 - nitrogen fixation
  • NH3 is used to make amino acids
  • energetically expensive
  • can only be done by some Bacteria and Archaea - not by eukaryotes
• Nutrient sources usually identified by element

  • S
  • Inorganic S
  • provided as salts (MgSO4)
  • Must be reduced to the level of S^2- used to make amino acids
  • assimilative sulfate reduction
  • Organic S
  • Pre-made amino acids (cysteine and methionine)
  • less energy to assimilate because they already have it
• Nutrient sources usually identified by element

  • C
  • refers to the source the majority of C in macromolecules
  • organisms places into 2 groups based on how they obtain C:
  • Heterotrophs
  • Autotrophs
• Heterotrophs

  • use organic carbon
  • one or more C is reduced (C atom with one or more H's)
  • Ex. Organic acids, alcohols, carbohydrates, amino acids
• Autotrophs

  • use inorganic carbon (CO2) as their sole source of carbon
  • requires energy to assimilate
  • photosynthesis
  • Ex. Anabaena