Examination of cell differentiation with anabaena

Question 1

How will we enrich for nitrogen-fixing cyanobacteria

Answer 1

By inoculating a mineral salts medium with a soil or freshwater sample.

Question 2

What does the mineral salt medium lack?

Answer 2

it lacks a source of combined nitrogen ( ammonia or nitrate)

It lacks a source of fixed carbon

Question 3

what is a cyanobacteria?

Answer 3

1. they are photoautotroph.

Question 4

What is Anabaena sp. ?

Answer 4

its a filamentous cyanobacterium that fixes nitrogen in specialized cells called heterocysts.

Question 5

Whats special about the heterocytes in anabaena sp.?

Answer 5

it has been modified in such a way to make them semi-anaerobic

Question 6

Physical aspects of heterocysts?

Answer 6

1. occur at regular intervals along filament
   (every tenth cell or so in the case of anabaena)
2. produced only when anabaena is growing in absence of combined nitrogen
3. larger than neighboring cells
4. apparent by phase contrast microscopy.

Question 7

what are characteristics of photoautotrophs?

Answer 7

they can fix CO2 using light as their energy source