2. pH tolerance

Question 1

What is an acidophile?

Answer 1

Grow well below pH 7

Question 2

What is a neutrophile?

Answer 2

Grow well at pH 7

Question 3

What is a alkaliphile

Answer 3

Grow well above pH 7

Question 4

What is an obligate acidophile?

Answer 4

Requires a low pH for growth because a high H+ is required for membrane stability

Question 5

Which 3 major aspects of cell function may be affected by acidic conditions?

Answer 5

1. capacity for nutrient acquisition and energy generation
2. cytoplasmic pH homeostasis
3. protection of proteins and DNA

Question 6

Main virulence factors of Helicobacter pylori? 4

Answer 6

Flagella
Urease
Adhesins
Vacuolating toxin

Question 7

What does H. pylori colonise in the stomach?

Answer 7

the mucin layer

Question 8

What does urease do?

Answer 8

hydrolyses the urea produced by gastric acid cells to ammonia and CO2 which neutralise the stomach acid

Question 9

What does UreI on H. pylori do?

Answer 9

Only allows urea entry if the extracellular pH is acidic

Question 10

Main virulence factors of salmonella typhimurium

Answer 10

Acid tolerance response
Adhesins
Invasion of mucosal cells
Type III secretion system

Question 11

Why is Fur important in the acid tolerance response?

Answer 11

It senses pH and regulates a subset of acid shock proteins

Question 12

What are some mechanisms of acid resistance in Gram + bacteria?

Answer 12

Proton pumps
Protein repair/DNA repair
Regulators
Altered metabolism
Production of alkali
Envelope alterations