Microbial Growth and Nutrition

Question 1

Macronutrients

Answer 1

• 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

Question 2

Protein-C,H,O,N (and S)

Answer 2

• Polymer of made of building blocks - amino acids
• > 50% of cell dry weight

Question 3

Lipids-C,H,O (and P)

Answer 3

• Building blocks = fatty acids and glycerol
• Ex. Phospholipids

Question 4

Carbohydrates - C,H,O (and N)

Answer 4

• Building blocks = sugars
• Ex. Polysaccharides and Peptidoglycan

Question 5

Nucleic Acids - C,H,O,N,P

Answer 5

• Building blocks = Nucleotides
• Ex. DNA and RNA

Question 6

Other Macronutrients - inorganic ions (K, Mg, Ca, Fe)

Answer 6

• 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+

Question 7

other functions

Answer 7

• Mg2+ helps stabilize membranes and nucleic acids
• Ca2+ helps stabilize cell walls, and plays a role in heat stability of
  endospores

Question 8

Micronutrients

Answer 8

• 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

Question 9

Growth factors

Answer 9

• 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

Question 10

What are the three classes of growth factors?

Answer 10

1. Amino Acids
2. Purines and Pyrimidines
3. Vitamins

Question 11

Amino Acids

Answer 11

20 amino acids are needed for protein synthesis

Question 12

Purines and Pyrimidines

Answer 12

• A, G, T, C and U
• Needed to make nucleotides, building blocks of DNA and RNA

Question 13

Vitamins

Answer 13

• Small molecules used to make organic cofactors
• Non-protein components required by some enzymes
  - Ex) Nicotinic acid → NAD+

Question 14

H,O

Answer 14

• No specific nutrient
• Found in H2O and organic media components

Question 15

P

Answer 15

• Usually provided as phosphate salt (PO43-)
  
  • Ex) K2HPO4, KH2PO4
• Reason: usually acquired as PO43- in the environment
• In freshwater systems PO43- is often limiting

Question 16

Limiting Nutrient

Answer 16

• In relatively low concentration compared to other nutrients
• When it runs out, growth stops despite other nutrients present

Question 17

Inorganic N

Answer 17

• Provided as salts (ex. KNO3 or NH4Cl)
• Must be reduced to NH3 – used to make amino acids (-NH2)

Question 18

Organic N

Answer 18

Provided as N rich organic molecules (ex. Amino acids or short peptides) -
does not need to be reduced

Question 19

Atmospheric N2

Answer 19

• 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

Question 20

Inorganic S

Answer 20

• Provided as salts (ex. MgSO4)
• Must be reduced to the level of S2- – used to make amino acids
  - Assimilative sulfate reduction

Question 21

Organic S

Answer 21

• Pre-made amino acids (cysteine and methionine)
• Less energy to assimilate

Question 22

C

Answer 22

• Refers to the source the majority of C in macromolecules
• Organisms placed into 2 groups based on how they obtain C:
• Heterotrophs
• Autotrophs

Question 23

Heterotrophs

Answer 23

• 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

Question 24

Autotrophs

Answer 24

• Use inorganic carbon (CO2) as their sole source of carbon
• Requires energy to assimilate
• Photosynthesis
• Ex) Anabaena

Question 25

Metabolism

Answer 25

The sum total of all of the chemical reactions that occur in a cell

Question 26

Catabolic Reaction (catabolism)

Answer 26

Energy-releasing metabolic reactions (e.g. fermentation, respiration)

Question 27

Anabolic Reactions (Anabolism)

Answer 27

Energy-requiring metabolic reactions (biosynthesis)

Question 28

How can Microorganisms be categorized?

Answer 28

1. Energy Source
2. Electron Source
3. Carbon Source

Question 29

Energy Source

Answer 29

• Chemo
• Photo

Question 30

Electron Source

Answer 30

• Organo
• Litho

Question 31

Carbon Source

Answer 31

• Hetero
• Auto

Question 32

Chemorganotrophs

Answer 32

Energy from chemical reactions involving
organic material

Question 33

Chemolithotrophs

Answer 33

Energy from inorganic chemical reactions

Question 34

Phototrophs

Answer 34

Energy from light

Question 35

Carbon Classes of Microorganisms

Answer 35

Microorganisms grouped with respect to carbon source:
1. Heterotrophs
2. Autotrophs

Question 36

Heterotrophs

Answer 36

Use organic carbon for building cell carbon
and biomass

Question 37

Autotrophs

Answer 37

• Use CO2 to synthesize cell carbon
• a.k.a. primary producers

Question 38

Classes of Culture Media

Answer 38

1. Defined Medium
2. Minimal Medium
3. Complex Medium

Question 39

Defined Medium

Answer 39

• Exact chemical composition is known
• Useful for studying metabolism

Question 40

Minimal Medium

Answer 40

A defined medium that provides the minimum nutritional requirements for growth (ie. No growth factors)

Question 41

Complex Medium

Answer 41

• 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

Question 42

Differential Medium

Answer 42

• 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

Question 43

Selective Medium

Answer 43

• 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

Question 44

Enriched Medium

Answer 44

• Supplemented with special nutrients to encourage the
  growth of fastidious bacteria
• Complex nutrient requirements – require many
  growth factors
  
  • Ex) Blood agar, chocolate agar