Block D - Microbial Growth

Question 1

What is the lag phase?

Answer 1

the period of adaptation and non-replication in the early stages of bacterial growth when bacteria is introduced to new conditions

Question 2

Why do we use pasteurisation?

Answer 2

lowers microbial numbers for preventing spoilage

Question 3

What is sterilisation?

Answer 3

kills all microbes

Question 4

Name 3 methods we use to sterilise?

Answer 4

UV, heat, sterile filtration

Question 5

How does UV light cause sterilisation?

Answer 5

kills bacteria by causing many mutations

Question 6

How does sterilisation occur through filtration

Answer 6

liquid or gas is passed through a filter with a pore size small enough to block the passage of most microbial organisms. pore size is usually 0.22µL, which is effective for trapping most bacteria

Question 7

Define bacteriocidal and describe what a graph would look like in terms of log cell number?

Answer 7

kills the bacteria, no cell growth but log cell number plateus and stays the same

Question 8

Define bacteriostatic and describe what a graph would look like in terms of log cell number?

Answer 8

inhibits bacterial growth but does not kill bacteria, log cell number stays the same

Question 9

Define bacteriolytic and describe what a graph would look like in terms of log cell number?

Answer 9

causes cell lysis and death via rupture of the cell wall/membrane, no growth and log cell number decreases

Question 10

Define antibiotic? (2 marks)

Answer 10

-antimicrobial compound
-produced by bacteria and fungi for killing or inhibiting the growth of bacteria

Question 11

What is a broad spectrum antibiotic, when is it used and give an example?

Answer 11

effective against a wide variety of gram postitive and gram negative bacteria and often used when the specific bacterial case is unknown. tetracycline

Question 12

What are 2 risks of using broad spectrum antibiotics?

Answer 12

-since it targets all bacteria, it can disrupt the good bacteria in your body (such as the bacteria found in your gut)
-can lead to antibiotic resistance

Question 13

What is a narrow spectrum antibiotic, when is it used and give an example?

Answer 13

these target a smaller, more specific group of bacteria, usually focusing on either gram-positive or gram-negative bacteria, or sometimes a single species. used when the causative bacteria has been identified. penicillin (effective against gram positive bacteria)

Question 14

What are 2 risks of using narrow spectrum antibiotics?

Answer 14

-not effective is the causative bacteria is not know
-if multiple bacteria is involved

Question 15

Name a narrow spectrum antibiotic that targets a specific species?

Answer 15

Isoniazid (targets Mycobacterium tuberculosis specifically)

Question 16

Describe the mechanism of action for different antifungal medicines? (3 marks)

Answer 16

-azoles like fluconazole inhibit the enzyme 14α-demethylase, which is involved in ergostreol synthesis
-polyenes like amphotericin B bind directly to ergosterol in the fungal cell membrane, creating pores that lead to lysis
-echinocandins like caspofungin inhibit the enzyme 3 β-glucan synthase, preventing the formation of β-glucan in the cell wall. This weakens the fungal cell wall, leading to cell lysis

Question 17

An autoclave is used for pasteurisation and uses ____?

Answer 17

heat

Question 18

What is the main idea of the Red Queen Hypothesis?

Answer 18

the theory that suggests that organisms must constantly evolve and adapt not just to survive in their own environment, but also to keep up with the evolving strategies of other organisms, particularly their predators, prey, and competitors

Question 19

What is the role of co-evolution in the Red Queen Hypothesis?

Answer 19

the concept of co-evolution, is where two or more species exert selective pressures on each other, leading to an ongoing cycle of adaptation

Question 20

What is the main idea of the Red Queen Hypothesis?

Answer 20

some species evolve to lose certain functions or traits that are costly to maintain, so they “offload” these functions by relying on these species performing the functions. by doing so they can conserve energy and resources, while still benefiting from the lost function as long as other species are performing it.

Question 21

What is quorum sensing?

Answer 21

its a form of cell to cell communication that allows bacteria to coordinate their behaviour based on their popultaion density

Question 22

Quorum sensing involves the release, detection and response to signalling molecules called _______

Answer 22

autoinducers

Question 23

Explain the role of the signalling molecules in quorum sensing (4 marks)

Answer 23

autoinducers accumulate in the environment as the population grows. once a certain threshold concentration of autoinducers is reached, the bacteria trigger a coordinated change in gene expression, leading to a collective behaviour that would be ineffective or inefficient if done individually

Question 24

Name the most commonly studied autoinducer in Gram-positive bacteria

Answer 24

peptides

Question 25

Name the most commonly studied autoinducer in Gram-negative bacteria

Answer 25

acyl-homoserine lactones (AHLs)

Question 26

What’s the importance of neutral mutations?

Answer 26

they could be the prerequisite to an advantagous/ disadvantagous mutation, enough neutral mutations could lead to a mutation that changes the selectivity

Question 27

What does the graph of adaption look like, describe it and explain why it looks the way it does.

Answer 27

adaptation is a step-up pattern not a straight line graph, this is because certain microbes get advantageous mutations and colonise the population (step-up)