14. Control of nodules

Question 1

Structure of the lecture

Answer 1

1. Control of bacteroid growth
2. Control of oxygen environment
3. Control of amino acids via symbiotic auxotrophy
4. Control of nitrogen fixation

Question 2

Overarching question of the lecture

Answer 2

Can bacteroids be considered organelles?

Question 3

What are the two types of bacteroid growth?

1

Answer 3

1. Indeterminate (Includes IRLC)
2. Determinate

Question 4

How do legumes control oxygen environment of Rhizobia?

2

Answer 4

1. Leghaemoglobin
2. NifA regulation
3. Fix cascades

Question 5

How do hosts control amino acid requirements in Rhizobia?

3

Answer 5

Symbiotic auxotrophy.

Bacteroids also require aap and bra ABC transporters for amino acid uptake

Question 6

How do plants control nitrogen fixation in Rhizobia?

4

Answer 6

1. Homocitrate cofactor from plants is required by Nitrogenase in Rhizobia
2. Bacteroids require sucrose and ammonia from the host legume photosynthesis
3. ‘Reward and sanction’ behaviour