Microbiologie: Physiologie micro-bactérienne

Question 1

What does croissance refer to?

Answer 1

Multiplication of cells

Question 2

What does culture refer to?

Answer 2

Growing in optimal conditions to facilitate identification, studying metabolism, and studying their potential uses

Question 3

What are the different ways to name microorganisms referring to their way of life? (energy, carbon, electrons)

Answer 3

Energy:

light: phototrophic
chemicals: chemotropic

Carbon:

CO2: autotroph

Organic molecules: heterotrophs

Electrons:

Inorganic: lithotroph

Organic: organotroph

Question 4

What are the different types of “milieu de culture”?

Answer 4

Defined:

Precise and known chemical composition

Goal? studying the impact of this composition on growth

Complex:

chemical composition not rigorously determined

goal? have anything present grow

Question 5

What are the different techniques of growth?

Answer 5

liquid —> bouillon, solid —> gélose

Gélose: adding agar to the bouillon —> allows for obtention of isolated and pure cultures

Question 6

What is agar?

Answer 6

algae extract that stays solid until around 45C

Question 7

What kind of colonies can grow in this environment?

Answer 7

Culture mixte: >1 type

Culture pure: 1 type

Question 8

What is the growth time for bacteria in this environment?

Answer 8

Depends on the species, conditions, and source of isolation

Most species have visible colonies after 18-24h of incubation at 35C:

• Enterobacteria
• Cocci gram+
• Non fermenting bacteria

Some species require longer incubation periods —> Legionella pneumophila (2-3 days) and Mycobacterium tuberculosis (2-6 weeks)

Question 9

What are the three ways to change your milieu de culture to facilitate growth?

Answer 9

1. Enrichis: adding products (ex: blood, vitamins, proteins) that promote growth for bacteria with specific complex or special nutrient requirements
2. Selective: adding growth inhibitors to inhibit the growth of unwanted bacteria and to favourize growth of desired ones
3. Différentiels: adding elements (sugar, pH indicators) to distinguish between the presence of different species

Question 10

What are the three important physicochemical characteristics to monitor to promote growth?

Answer 10

1. Temperature:
   
   • Psychrophiles (-10 to 25 C)
   • Mésophiles (20 to 50 C)
   • Thermophiles (50 to 100 C)
2. pH
   
   • extreme acidophiles
   • acidophiles
   • neutrophiles
   • alkalophiles
   • extreme alkalophiles
3. Oxygen
   
   • Strict aerobic (need O2)
   • Facultative aerobic (better in O2)
   • Strict anaerobic (cannot grow in presence of O2)
   • Aerotolerant anaerobic (O2 has no effect)
   • Microaerophiles (grow in low conc. of O2)

Question 11

Specifications for oxygen conditions:

Answer 11

5 TYPES TO KNOW

Question 12

What is a facteur de croissance?

Answer 12

Essential metabolite that the microbe isn’t able to synthesize

Must be provided through aliments

Can intervene at any stage of their metabolism

Small molecule (amino acid, nucleotide base, vitamin, heme, ion)

Question 13

How do you measure bacterial growth?

Answer 13

Courbe de croissance

Question 14

What are the different phases on the courbe de croissance? (6)

Answer 14

1. Latence: period between formation of bouillon and the time the colony starts to grow (corresponds to the necessary delay for enzymes to be synthesized)
2. Acceleration: start dividing very fast
3. Exponential: optimal growth of culture… this is when bacteria start producing exotoxins
4. Ralentissement: start missing nutrients and the production of waste starts to impact the bacterial growth
5. Stationnaire: maximal density is attained… equilibrium between forming and dying
6. Décroissance: exponential decrease of viable bacteria… when they die, gram- bacteria release their endotoxins

Question 15

How are sugars catabolized to form energy?

Answer 15

IF OXYGEN… CELLULAR RESPIRATION

Question 16

How does respiratory metabolism work in aerobes in presence of oxygen?

Answer 16

Breaking of C-C or C-H bonds when glucose is degraded into CO2 forms energy which is then stored as ATP

Glucose is transformed into pyruvate during glycolysis which is then degraded into CO2 during Krebs

Protons and electrons are captured by oxygen and form water

During this process, energy is made and stored as ATP

Question 17

How does respiratory metabolism work if there is no O2?

Answer 17

Some organisms can use inorganic compounds as the final acceptor in the electron transport chain instead of oxygen THIS IS NOT FERMENTATION

Question 18

What is fermentation and how does it work?

Answer 18

There is no Krebs therefore the only energy produced happens in glycolysis (only 2x ATP produced)

NADH is reoxydized giving up its electrons to an organic compound which forms a fermentation product…

Question 19

What are the types of fermentation? (7)

Answer 19

1. Alcoolique: final product is ethanol (wine, bread, beer)
2. Homolactique: final product is lactic acid (cheese and yogurt)
3. Hétérolactique: final product are products similar to lactic acid (kefir)
4. Propionique: final product is propionic acid (yucky cheese)
5. Acides mixtes: multiple final products (lactic acid, succinic acid, acetic acic, etc.)
6. Acétonobutylique: final products are acetone and butanol
7. Butyrique: final product is butyric acid

Question 20

What are some industrial uses of fermentation?

Answer 20

Question 21

What are the main difference between respiration aérobie vs anaérobie vs fermentation? (4 categories)

Answer 21

1. Growth conditions

• Aérobie: aerobic
• Anaérobie: anaerobic
• Fermentation: either aerobic or anaerobic

2. Final electron acceptor

• Aérobie: O2
• Anaérobie: Inorganic substance
• Fermentation: Organic substance

3. Phosphorylation type used to produce ATP:

• Aérobie: substrate and oxydative
• Anaérobie: substrate and oxydative
• Fermentation: substrate

4. # of ATP produced (ISH)

• Aérobie: 30 for eukaryotes and 32 for prokaryotes
• Anaérobie: variable but less than 32 and more than 2
• Fermentation: 2 (from glycolysis)

Question 22

How do bioreactors work?

Answer 22

An apparatus for growing organisms (yeast, bacteria, or animal cells) under controlled conditions. Used in industrial processes to produce pharmaceuticals, vaccines, or antibodies. Also used to convert raw materials into useful byproducts such as in the bioconversion of corn into ethanol.