Chapter 3 - Microbial Growth and Nutrition

Question 1

Macronutrients

Answer 1

Elements required in large amounts to build macromolecules - C, H, O, N, P and S makeup >90% of the dry of the cell

Question 2

Protein

Answer 2

C, H, O, N (and S)
Polymer made of building blocks - amino acids
- >50% of cell dry weight

Question 3

Lipids

Answer 3

C, H, O (and P)
Building blocks = fatty acids and glycerol
ex. Phospholipids

Question 4

Carbohydrates

Answer 4

C, H, O, (and N)
Building blocks = sugars
ex. polysaccharides and peptidoglycan

Question 5

Nucleic acid

Answer 5

C, H, O, N, P
Building blocks = nucleotides
ex. DNA and RNA

Question 6

Other macronutrients

Answer 6

Inorganic ions (K, Mg, Ca, Fe)
Often serve as metabolic co-factors

Question 7

Metabolic co-factors

Answer 7

Non-protein component required for enzyme function

Question 8

Enzymes involved in protein synthesis require

Answer 8

K+

Question 9

Cytochrome require

Answer 9

Fe2+

Question 10

Mg2+ help

Answer 10

Stabilize membranes and nucleic acids

Question 11

Ca2+ helps

Answer 11

Stabilize cell walls and plays a role in heat stability of endospores

Question 12

Micronutrients

Answer 12

Elements required in very small amounts (trace elements)

Usually serve as cofactors

Question 13

Se is required to make

Answer 13

Unusual amino acid selenocysteine

Question 14

Growth factors

Answer 14

Small organic molecules required for growth

Question 15

Classes of growth factors

Answer 15

Amino acids, purines and pyrimidines, and vitamins

Question 16

How many acids are required for protein synthesis?

Answer 16

20 amino acids

Question 17

Purines and pyrimidines

Answer 17

A, G, T, C, and U

Needed to make nucleotides, building blocks of DNA and RNA

Question 18

Vitamins

Answer 18

Small molecules used to make organic cofactors

Non-protein components required by some enzymes

Question 19

Growth factor requirements

Answer 19

Many have no growth factors - E. coli

Some bacteria require many - leuconostoc mesenteroides

Question 20

H and O

Answer 20

No specific nutrient

Found in H2O and organic media components

Question 21

P

Answer 21

Usually provided as phosphate salt PO4^3- acquired from the environment
In freshwater systems, it is often limiting

Question 22

Limiting nutrient

Answer 22

When it runs out, growth stops despite other nutrients present

Question 23

Inorganic N

Answer 23

Provided as salts

Must be reduced to NH3 - used to make amino acids (-NH2)

Question 24

Organic N

Answer 24

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

Question 25

Atmospheric N2

Answer 25

N2 is reduced to 2NH3 - nitrogen fixation
NH3 is used to make amino acids
Energetically expensive
Only done by some bacteria and archaea

Question 26

Inorganic S

Answer 26

Provided as salts

Must be reduced to the level of S^2- to make amino acids - assimilative sulfate reduction

Question 27

Organic S

Answer 27

Pre-made amino acids (cysteine and methionine)

Less energy to assimilate

Question 28

Heterotrophs

Answer 28

Use organic carbon

One or more C is reduced

Question 29

Autotrophs

Answer 29

Use inorganic carbon (CO2) as their sole source of carbon

Requires energy to assimilate - photosynthesis

Question 30

Defined medium

Answer 30

Exact chemical composition is known

Question 31

Minimal medium

Answer 31

A defined medium that provides the minimum nutritional requirements for growth (no growth factors)

Question 32

Complex medium

Answer 32

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 33

Differential medium

Answer 33

Allows different bacteria to be distinguished

Question 34

Blood agar

Answer 34

T-soy plate + 5% sheep's blood
Allows differentiation of hemolytic bacteria
alpha - incomplete destruction
beta - complete destruction
gamma - no destruction

Question 35

Selective medium

Answer 35

Contain ingredients that inhibit the growth of unwanted microbes

Question 36

Mannitol salt agar

Answer 36

Contains very high salt - only halotolerant bacteria will grow
Used to isolate staphylococci from skin

Question 37

Enriched medium

Answer 37

Supplemented with special nutrients to encourage the growth of fastidious bacteria
Complex nutrient requirements - require many growth factors

Question 38

Metabolism

Answer 38

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

Question 39

Catabolic reactions (catabolism)

Answer 39

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

Question 40

Anabolic reactions (anabolism)

Answer 40

Energy-requiring metabolic reactions (biosynthesis)

Question 41

Chemorganotrophs get their energy from

Answer 41

chemical reactions involving organic material

Question 42

Chemolithorophs get their energy from

Answer 42

inorganic chemical reactions

Question 43

Phototrophs

Answer 43

Energy from light

Question 44

Heterotrophs carbon source

Answer 44

Organic carbon

Question 45

Autotrophs carbon source

Answer 45

CO2

Question 46

What is a defined medium useful for?

Answer 46

Studying metabolism