IA. General Microbiology | 2. Bacterial metabolism. The growth and reproduction of bacteria.

Question 1

I. Bacterial metabolism
1. What is Bacterial Metabolism?

Answer 1

How bacteria gets energy and nutrients

Question 2

I. Bacterial metabolism
2. What are the main types of Bacterial Metabolism?

Answer 2

1. Heterotrophic
2. Autotrophic
3. Phototrophic

Question 3

I. Bacterial metabolism - Heterotrophic
3A. What are characteristics of Heterotrophic?

Answer 3

• Heterotrophic bacteria
  depend on preformed food for nutrition
• Energy yielding catabolic reaction: transferring electrons from one molecule to another to produce ATP
• Some metabolize sugars and carbohydrates to produce energy – require enzymes to degrade polysaccharides into usable sugar units

Question 4

I. Bacterial metabolism - Heterotrophic
3B. How does heterotrophic bacteria use carbohydrates?

Answer 4

• Sugars – produce energy via fermentation and respiration
  (Carbohydrates used in glycolysis and pentose phosphate pathways in eukaryotic cells)

Question 5

I. Bacterial metabolism - Heterotrophic
3C. How does fermentation happen in heterotrophic bacteria?

Answer 5

Fermentation → anaerobic process that takes places in the absence of any external electron acceptor.
- Sugar is broken down into smaller organic molecules → catabolic rxn that results in the formation of ATP
- Result in production of large quantities of organic end products and relatively small out of energy per glucose molecule consumed
- Variety of fermentation pathways and this helps ID the bacteria by their end products

Question 6

I. Bacterial metabolism - Heterotrophic
3D. How does Respiration happen in heterotrophic bacteria?

Answer 6

Respiration → more energy is available through this process
■ Electrons from molecules of sugar are transferred to another inorganic molecule
■ Aerobic respiration uses oxygen as the final electron acceptor — sugar broken down and 38 ATP per molecule of glucose
■ Anaerobic conditions use inorganic molecules (nitrate, sulfate, carbon dioxide) as the final electron acceptor. Lower yield than aerobic respiration, but still higher than fermentation

Question 7

I. Bacterial metabolism - Autotrophic
4A. What are the features of autotrophic bacteria?

Answer 7

• Autotrophic bacteria are capable synthesizing their food from simple inorganic nutrients

Question 8

I. Bacterial metabolism - Autotrophic
4B. How do Autotrophic bacteria carry out metabolism?

Answer 8

• Use light energy through photosynthetic pigment and convert to ATP
• Synthesize all their cell constituents using carbon dioxide as the carbon source - most common way is through the Calvin Cycle and the acetyl-CoA pathway.
• Depends on the ability of the cell to carry out photosynthesis or aerobic respiratory metabolism – maintain carbon fixation

Question 9

I. Bacterial metabolism - Autotrophic
4C. What is Calvin cycle?

Answer 9

● Calvin cycle is the reaction of ribulose 1,5-bisphosphate with carbon dioxide, yielding two molecules of 3-phosphoglycerate, a precursor to glucose.

Question 10

I. Bacterial metabolism - Phototrophic
5A. What are phototrophs?

Answer 10

• Phototrophs are organisms that carry out photon capturing to produce complex organic compounds such as carbohydrates) and acquire energy

Question 11

I. Bacterial metabolism - Phototrophic
5B. How do phototrophs carry out metabolism?

Answer 11

● Requires electrons to be available to replace electrons that are consumed during biosynthetic rxns
● Electrons are passed through an electron transport chain, with the generation of energy by formation of a proton gradient and concomitant ATP synthesis.

Question 12

II. Cultivation of bacteria
1. What is cultivation of bacteria?

Answer 12

Multiplying microorganism by letting them reproduce in predetermined culture media under controlled laboratory conditions
● Bacteria grow and divide by binary fission → population growth
● Optimal environment → cell count grows exponentially
● Generation time → until the cell mass doubles normally 20-40 mins except mycobacteria (20hrs)

Question 13

II. Cultivation of bacteria
2. Make bacteria growth curve

Answer 13

Question 14

II. Cultivation of bacteria
3. What is the requirement of bacteria growth?

Answer 14

• Physical: Temp, Atmosphere, pH, Osmotic P
• Chemical: Culture medium

Question 15

II. Cultivation of bacteria - Physical Aspects
4A. What are the 4 physical aspects of bacteria cultivation?

Answer 15

1. Temperature
2. Atmosphere
3. pH
4. Osmotic pressure

Question 16

II. Cultivation of bacteria - Physical Aspects
4B. Describe temperature, a physical aspect of bacteria cultivation

Answer 16

● Psychrophiles - cold loving (< 20°C)
● Mesophiles - moderate loving
(20-40°C)
● Thermophiles - heat loving (> 40°C)

Question 17

II. Cultivation of bacteria - Physical Aspects
4C. Describe Atmosphere, a physical aspect of bacteria cultivation

Answer 17

● Aerobic - need O2 to grow
● Anaerobic - do NOT need O2 to grow
● Obligate aerobic → NEED O2 to survive
● Obligate anaerobic → cannot survive in the presence of O2
● Facultative Anaerobic → can grow w/out O2, but if O2 present they can use it
● Microaerophilic → need low [O2]
● Aeroteolerant → cannot use O2 but are not harmed by it
=> Microbes that use O2 produce more than energy than those that do not use it

Question 18

II. Cultivation of bacteria - Physical Aspects
4D. Describe pH, a physical aspect of bacteria cultivation

Answer 18

● Acidophiles: <5.5
● Neutrophiles: 5.5 - 8 (most bacteria)
● Alkaliphiles: >8

Question 19

II. Cultivation of bacteria - Physical Aspects
4D. Describe Osmotic P, a physical aspect of bacteria cultivation

Answer 19

● Most bacteria need isotonic solution → cytoplasm in most bacteria has a greater osmolarity than its environment
● Hypertonic media → water will leave cell = plasmolysis
● Isotonic media → bacteria are in equilibrium with their environment

Question 20

II. Cultivation of bacteria - Chemical Aspects
5. What does culture medium contain?

Answer 20

Culture Medium contains:
- Water
- Source of carbon and energy
- Source of nitrogen
- Trace elements
- Buffer sol’n
- Growth factors and agar (polysaccharide extracted from marine algae)

Question 21

II. Cultivation of bacteria - Chemical Aspects
6. What are the 3 types of culture media?

Answer 21

1. Consistency
2. Nutritional Components
3. Functional Use

Question 22

II. Cultivation of bacteria - Chemical Aspects
7A. Classify the culture media based on consistency

Answer 22

a. Liquid media (bouillon)
→ bacteria grows uniformly producing general turbidity
(cloudiness) - no agar

b. Semi-solid media
→ soft and show bacterial movement - 0.5% agar is added

c. Solid Media
→ petri dish that contains a growth medium used to culture

Question 23

II. Cultivation of bacteria - Chemical Aspects - Culture media (consistency)
7B. What are the features of Liquid media (bouillon)?

Answer 23

Liquid media (bouillon)
→ bacteria grows uniformly producing general turbidity
(cloudiness) - no agar

Question 24

II. Cultivation of bacteria - Chemical Aspects - Culture media (consistency)
7C. What are the features of Semi-solid media?

Answer 24

Semi-solid media → soft and show bacterial movement - 0.5% agar is added

Question 25

II. Cultivation of bacteria - Chemical Aspects - Culture media (consistency)
7D. What are the features of solid media?

Answer 25

Solid Media → petri dish that contains a growth medium used to culture microorganisms – 2-3% agar is added

Question 26

II. Cultivation of bacteria - Chemical Aspects
8A. Classify the culture media based on Nutritional Components

Answer 26

a. Simple media
→ peptone water, nutrient agar - support non-fastidious bacteria

b. Complex media
→ yeast extracts or casein hydrolysate to help growth

c. Synthetic or chemically defined media
→ used for research and every component is well known

Question 27

II. Cultivation of bacteria - Chemical Aspects - Culture media (Nutritional Components)
8B. What are the features of Simple media?

Answer 27

Simple media → peptone water, nutrient agar - support non-fastidious bacteria

Question 28

II. Cultivation of bacteria - Chemical Aspects - Culture media (Nutritional Components)
8C. What are the features of Complex media?

Answer 28

Complex media → yeast extracts or casein hydrolysate to help growth

Question 29

II. Cultivation of bacteria - Chemical Aspects - Culture media (Nutritional Components)
8D. What are the features of Synthetic or chemically defined media?

Answer 29

Synthetic or chemically defined media
→ used for research and every component is well known

Question 30

II. Cultivation of bacteria - Chemical Aspects
9A. Classify the culture media based on Functional Use

Answer 30

1. Enriched media
   - used to isolate pathogen from a mixed culture (blood or chocolate agar)
2. Selective media
   - inhibitory substance is added to solid media
3. Differential media
   - diff bacteria can be recognized based on colony colour
4. Selective - differential media
   - eosin methylene blue agar (EMB)
5. Transport culture media and transport media
6. Anaerobic media

Question 31

II. Cultivation of bacteria - Chemical Aspects - culture media based on Functional Use
9B. What are the features of Enriched media?

Answer 31

Enriched media - used to isolate pathogen from a mixed culture (blood or chocolate agar)

Question 32

II. Cultivation of bacteria - Chemical Aspects - culture media based on Functional Use
9C. What are the features of Selective media?

Answer 32

Selective media - inhibitory substance is added to solid media

Question 33

II. Cultivation of bacteria - Chemical Aspects - culture media based on Functional Use
9D. What are the features of Differential media?

Answer 33

Differential media - diff bacteria can be recognized based on colony colour

Question 34

II. Cultivation of bacteria - Chemical Aspects - culture media based on Functional Use
9E. What are the features of Selective - differenti media?

Answer 34

Selective - differential media - eosin methylene blue agar (EMB)

Question 35

II. Cultivation of bacteria - Chemical Aspects
10. What are the features of Agar?

Answer 35

Agar has high melting point (55-60°C) and solidifies at 40-45°C. Slant, Deep and Plate Agar