Lecture 1

Question 1

How is iron acquired by bacteria

Answer 1

1. Transporters
2. Siderophores
3. Transferrin/ Lactoferrin binding proteins

Question 2

What are siderophores

Answer 2

Low molecular weight molecules that chelate iron with a high and specific affinity

Question 3

What is the Fenton reaction and what is it caused by

Answer 3

The Fenton reaction is a cascade of reactive oxygen species as a result of uncontrolled iron resulting in hydroxyl ions which harm DNA

Question 4

Where do reactive oxygen species come from?

Answer 4

Aerobic metabolism, environmental sources such as competing organisms. For example, S. Aureus produces H2O2 to kill other bacteria in its environment, neutrophils and macrophages (use ROS to kill off bacteria)

Question 5

How is iron uptake regulated

Answer 5

Low iron requires uptake systems and high iron turns off uptake systems.

Controlled by FUR (ferric uptake regulator).

When there’s too much iron, FUR binds to the repressor and stops transcription of uptake siderophore transporters

Question 6

What is ferric uptake regulator

Answer 6

It’s a small protein (17kDA) which is a transcriptional repressor, preventing transcription upstream.

It responds to the level or iron. Iron acting as the co-repressor.

Question 7

What genes encode for FE(II) uptake siderophore transporters in S.aureus

Answer 7

sstA and sirA

Question 8

What genes encode for iron-hydroxamate uptake transporters in S. aureus

Answer 8

fhuA, fhuC, fhuD

Question 9

What does FUR regulate

Answer 9

FUR positively regulates catalase to prevent the fenton reaction. Catalase is an enzyme that removes H2O2 into H2O and O2

FUR negatively regulates iron transporters

Question 10

Example of a catalase in S.aureus

Answer 10

KatA.

Question 11

What is PerR and where does it bind

Answer 11

PerR is a peroxide regulator. It’s a Fur homologue

It binds to PerR box and represses gene expression of catalase (as a result of peroxide stress)

Question 12

What does PerR regulate

Answer 12

It regulates iron storage and antioxidants such as Fur, MrgA, TrxB, ferritin, catalase, AhpC peroxidase

Question 13

What is manganese essential for

Answer 13

It’s an essential cofactor in bacteria needed for sugar metabolism, signal transduction and oxidative stress resistance.

It’s also important for the detoxification of ROS

Question 14

What are the two Mn2+ transporters and what are they controlled by

Answer 14

MntA (major transporter) and MntH.

They’re controlled by MntR (Manganese transport regulator). MntR represses the transcription of mntA in the presence of Mn2+

Question 15

What is regulation of Mn2+ transport crucial for

Answer 15

Critical for maintaining metal homeostasis

Question 16

What are the roles of Mn2+

Answer 16

• Acts as a superoxide scavenger, removing superoxide’s.

Having enough Mn2+ means that you can repress and prevent Fenton reaction.

In S.aureus, high levels of Mn2+ means they don’t need oxidative stress resistance enzymes

Question 17

Equation of Mn2+ scavenging

Answer 17

Mn2+ + O2- +2H+ -> Mn3+ + H2O2 -> Mn2+ +O2 + 2H2O

Question 18

What is Mn2+ an energetically favourable alternative of

Answer 18

Superoxide dismutates e.g. SODA and SODM

Question 19

What do SODs do

Answer 19

Sods prevent accumulation of O2- which prevents bacterium from damage against products derived from O2- such as OONO-

Question 20

How does calprotectin protect the host from S.aureus

Answer 20

Calprotectin is a 10kDa:S100A9 protein made by neutrophils which sequesters Mn2+, inhibiting S.aureus growth and protecting the host.