Bacterial Metabolism

Question 1

What is metabolism?

Answer 1

Metabolism is the total of all chemical reactions occurring inside the cell for them to survive and reproduce. It consists of two opposing chemical reactions in cells: catabolism and anabolism

Question 2

What is catabolism and anabolism?

Answer 2

Catabolism = breakdown of foodstuffs into smaller molecules to generate energy

Anabolism = uses the energy from catabolism to drive the synthesis of other molecules

Question 3

What is ATP?

Answer 3

Energy is produced in the form a molecular called Adenosine Triphosphate (ATP)
It is the currency and store of energy in cells and drives a variety of chemical actions
Releases energy when hydrolysed back to ADP

Question 4

How does bacteria metabolise?

Answer 4

Aerobic / Anaerobic respiration and fermentation

Question 5

What is the difference between aerobic and anaerobic respiration?

Answer 5

Aerobic respiration uses oxygen and occurs in most cells

Anaerobic respiration does not use ooxygen and occurs mostly in prokaryotes

Question 6

What is the input and output of aerobic/anaerobic respiration?

Answer 6

IN = carbohydrates, proteins, lipids, lights, and organic molecules

OUT = CO2 / H2O, inorganic molecules, small organic molecules

Question 7

How does the bacterial population grow?

Answer 7

Bacteria grow and replicate by binary fission (1 - 2 - 4 - 8)
Requires energy to grow and follows a standard growth curve

Question 8

How is bacteria grown?

Answer 8

Solid or liquid, culture media is used to grow, store, and transport bacteria

Question 9

How is the culture media decided for different bacteria?

Answer 9

Type of media defined by:

1. Chemical composition (defined = synthetic, comlex = broth)
2. Physical nature (liquid, semi-solidm solid = agar)
3. Function (supportive = general purpose, enriched, selective or differential = broth)

Question 10

What are the ideal growth conditions for bacteria?

Answer 10

Temperature usually 37 C but varies from 0 - 121 C
Most like pH 7 - 8, but can vary from pH 0 - 11

Strict aerobes require oxygen
Facultative aerobes prefer oxygen
Facultative anaerobes prefer no oxygen
Strict anaerobes require no oxygen

Question 11

What are the different methods of assessing bacterial growth?

Answer 11

Cell counting under a microscope
Serial dilution and plating on agar (colony forming units)
Optical density of culture
qPCR

Question 12

What are the different growth phases for bacteria?

Answer 12

1. Lag phase
2. Exponential or logarithmic phase
3. Stationary phase
4. Death or lysis

Question 13

What are the characteristics of the lag phase?

Answer 13

Adjustment period
Bacteria adapting to new environment
Replicating chromosomes to build new proteins / enzymes

Question 14

What are the characteristics of the exponential phase?

Answer 14

Cells growing and dividing
Maximal growth
Continues until nutrients exhausted or ihibitory molecules accumulate

Question 15

What are the characteristics of the stationary phase?

Answer 15

Cell numbers stop increasing and DNA replication is arrested
Cells produce new proteins to enhance survival during starvation

At this stage, greater resistance to antibiotics via cell wall crosslinking
Spore formation

Question 16

What are the characteristics of the death phase?

Answer 16

Cells stop growing, even if supplied with new medium

Cell lysis

Question 17

How do bacterial growth phases correlate to the oral environment?

Answer 17

Lag phase = immediately after meal, adjusting to new influx nutrients

Exponential phase = after meal, post adjustment, cells divding maximally

Stationary phase = period of fasting in between meals, nutrients limited, bacteria suseptible to antimicrobials

Death phase = variable between bacteria

Question 18

How is nutrient acquisition impacted by the oral envirnment?

Answer 18

Oral bacteria breakdown complex macromolecules
Diet, saliva, and gingival cervicular fluid all play a part
Enzymes for breakdown = protases, amylases, and lipases

Question 19

How does oxygen in the oral environment impact the bacteria there?

Answer 19

Strict aerobic bacteria needs oxygen = not many in dental plaque

Facultative aerobic bacteria only prefer oxygen just as facultative anaerobes do no prefer oxygen such as stretococci

Strict anaerobes require no oxygen, many of these are associated with periodontal disease and are present in subgingival plaque