Macronutrients
Elements required in large amounts to build macromolecules - C, H, O, N, P and S makeup >90% of the dry of the cell
Protein
C, H, O, N (and S)
Polymer made of building blocks - amino acids
- >50% of cell dry weight
Lipids
C, H, O (and P)
Building blocks = fatty acids and glycerol
ex. Phospholipids
Carbohydrates
C, H, O, (and N)
Building blocks = sugars
ex. polysaccharides and peptidoglycan
Nucleic acid
C, H, O, N, P
Building blocks = nucleotides
ex. DNA and RNA
Other macronutrients
Inorganic ions (K, Mg, Ca, Fe) Often serve as metabolic co-factors
Metabolic co-factors
Non-protein component required for enzyme function
Enzymes involved in protein synthesis require
K+
Cytochrome require
Fe2+
Mg2+ help
Stabilize membranes and nucleic acids
Ca2+ helps
Stabilize cell walls and plays a role in heat stability of endospores
Micronutrients
Elements required in very small amounts (trace elements)
Usually serve as cofactors
Se is required to make
Unusual amino acid selenocysteine
Growth factors
Small organic molecules required for growth
Classes of growth factors
Amino acids, purines and pyrimidines, and vitamins
How many acids are required for protein synthesis?
20 amino acids
Purines and pyrimidines
A, G, T, C, and U
Needed to make nucleotides, building blocks of DNA and RNA
Vitamins
Small molecules used to make organic cofactors
Non-protein components required by some enzymes
Growth factor requirements
Many have no growth factors - E. coli
Some bacteria require many - leuconostoc mesenteroides
H and O
No specific nutrient
Found in H2O and organic media components
P
Usually provided as phosphate salt PO4^3- acquired from the environment
In freshwater systems, it is often limiting
Limiting nutrient
When it runs out, growth stops despite other nutrients present
Inorganic N
Provided as salts
Must be reduced to NH3 - used to make amino acids (-NH2)
Organic N
Provided as N rich organic molecules (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
Only done by some bacteria and archaea
Inorganic S
Provided as salts
Must be reduced to the level of S^2- to make amino acids - assimilative sulfate reduction
Organic S
Pre-made amino acids (cysteine and methionine)
Less energy to assimilate
Heterotrophs
Use organic carbon
One or more C is reduced
Autotrophs
Use inorganic carbon (CO2) as their sole source of carbon
Requires energy to assimilate - photosynthesis
Defined medium
Exact chemical composition is known
Minimal medium
A defined medium that provides the minimum nutritional requirements for growth (no growth factors)
Complex medium
Exact chemical composition is not known
Often made from meat or yeast extracts
Supply a variety of growth factors
ex. T-soy broth and plates
Differential medium
Allows different bacteria to be distinguished
Blood agar
T-soy plate + 5% sheep's blood Allows differentiation of hemolytic bacteria alpha - incomplete destruction beta - complete destruction gamma - no destruction
Selective medium
Contain ingredients that inhibit the growth of unwanted microbes
Mannitol salt agar
Contains very high salt - only halotolerant bacteria will grow
Used to isolate staphylococci from skin
Enriched medium
Supplemented with special nutrients to encourage the growth of fastidious bacteria
Complex nutrient requirements - require many growth factors
Metabolism
The sum total of all of the chemical reactions that occur in a cell
Catabolic reactions (catabolism)
Energy-releasing metabolic reactions (e.g. fermentation, respiration)
Anabolic reactions (anabolism)
Energy-requiring metabolic reactions (biosynthesis)
Chemorganotrophs get their energy from
chemical reactions involving organic material
Chemolithorophs get their energy from
inorganic chemical reactions
Phototrophs
Energy from light
Heterotrophs carbon source
Organic carbon
Autotrophs carbon source
CO2
What is a defined medium useful for?
Studying metabolism