Microbial Growth and Nutrition Flashcards
Macronutrients
- elements required in large amounts to build macromolecules
- The building blocks of cell material
- C,H,O,N,P and S makeup >90% of the dry weight of the cell
Protein-C,H,O,N (and S)
- Polymer of 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 Acids - 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
- Non-protein component required for enzyme function
- Enzymes involved in protein synthesis require K+
- Cytochromes (e- carriers) require Fe2+
other functions
- Mg2+ helps 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 for enzymes
- Ex) Mn, Zn, Co, Ni, Cu, Mo
- Se is required to make the unusual amino acid selenocysteine
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
What are the 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
Vitamins
- Small molecules used to make organic cofactors
- Non-protein components required by some enzymes
- Ex) Nicotinic acid → NAD+
H,O
- No specific nutrient
- Found in H2O and organic media components
P
- Usually provided as phosphate salt (PO43-)
- Ex) K2HPO4, KH2PO4
- Reason: usually acquired as PO43- in the environment
- In freshwater systems PO43- is often limiting
Limiting Nutrient
- In relatively low concentration compared to other nutrients
- When it runs out, growth stops despite other nutrients present
Inorganic N
- Provided as salts (ex. 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
Inorganic S
- Provided as salts (ex. MgSO4)
- Must be reduced to the level of S2- – used to make amino acids
- Assimilative sulfate reduction
Organic S
- Pre-made amino acids (cysteine and methionine)
- Less energy to assimilate
C
- Refers to the source the majority of C in macromolecules
- Organisms placed into 2 groups based on how they obtain C:
- Heterotrophs
- Autotrophs
Heterotrophs
- Use organic carbon
- One or more C is reduced (ie. a 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
Metabolism
The sum total of all of the chemical reactions that occur in a cell
Catabolic Reaction (catabolism)
Energy-releasing metabolic reactions (e.g. fermentation, respiration)
Anabolic Reactions (Anabolism)
Energy-requiring metabolic reactions (biosynthesis)
How can Microorganisms be categorized?
- Energy Source
- Electron Source
- Carbon Source
Energy Source
- Chemo
- Photo
Electron Source
- Organo
- Litho
Carbon Source
- Hetero
- Auto
Chemorganotrophs
Energy from chemical reactions involving
organic material
Chemolithotrophs
Energy from inorganic chemical reactions
Phototrophs
Energy from light
Carbon Classes of Microorganisms
Microorganisms grouped with respect to carbon source:
1. Heterotrophs
2. Autotrophs
Heterotrophs
Use organic carbon for building cell carbon
and biomass
Autotrophs
- Use CO2 to synthesize cell carbon
- a.k.a. primary producers
Classes of Culture Media
- Defined Medium
- Minimal Medium
- Complex Medium
Defined Medium
- Exact chemical composition is known
- Useful for studying metabolism
Minimal Medium
A defined medium that provides the minimum nutritional requirements for growth (ie. 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
- Ex) Blood agar – T-soy plate + 5% sheep’s blood
- Allows differentiation of hemolytic bacteria
- a – incomplete destruction of blood cells
- b – complete destruction
- g – no destruction
Selective Medium
- Contain ingredients that inhibit the growth of
unwanted microbes - Allow only specific microbes to grow
- Ex) Mannitol salt agar
- Contains very high salt, so that 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- Ex) Blood agar, chocolate agar
