1. Questions for lab
Halobacterium is an extremophile. In which conditions is it able to grow? In which conditions does it grow best?
In what ways do halo change to respond to its environment?

2. Growth of halobacterium in light and dark, with and without oxygen

3. Remember ATP
Cells need ATP for nearly all cellular processes that require energy, including growth
Therefore, halo must be able to make ATP in the conditions that allow them to grow

4. MORE OUTPUT INPUT stored energy stored energy LESS P ATP ENERGY
FOR CELLULAR
WORK
CHEMICAL
ENERGY
ADP + P P
LESS
stored energy

5. Results from lab
In what ways do halo change to respond to its environment?
Becomes more purple

6. 1 2 3 4 5 What makes halobacterium purple?
What is the purple membrane protein made of? 3
What is the purpose of the purple membrane protein? 4
Why do halobacterium grow better in the light? 5
What is the effect of the amount of light on the amount of purple membrane protein?

7. Halo have a purple membrane protein called bacteriorhodopsin (BR)
Halobacterium cell
Bacteriorhodopsin (BR)

8. Halo have a purple membrane protein called bacteriorhodopsin (BR)
Halobacterium cell
Bacteriorhodopsin (BR)

9. Halo have a purple membrane protein called bacteriorhodopsin (BR)
Cell membrane

10. Bop + retinal = bacteriorhodopsin (BR)
Bacteriorhodopsin (BR) is made from a protein called bop and the molecule retinal
Bop + retinal = bacteriorhodopsin (BR)
Cell membrane
Retinal
Bacteriorhodopsin
(BR)
Bop protein

11. BR converts light energy into chemical energy for making ATP
Halobacterium cell
ATP
ATP
ATP
ATP
ATP
Bacteriorhodopsin (BR)
Note: other proteins are required for this process, but we will simplify and focus on BR

12. BR converts light energy into chemical energy for making ATP
Halobacterium cell
ATP
ATP
ATP
ATP
ATP
Bacteriorhodopsin (BR)
Note: other proteins are required for this process, but we will simplify and focus on BR

13. BR converts light energy into chemical energy for making ATP
Bacteriorhodopsin
(BR)
Cell membrane
LIGHT
ADP + P
ATP

14. BR converts light energy into chemical energy for making ATP
LIGHT PRESENT
Bacteriorhodopsin
(BR)
Cell membrane
LIGHT
ADP P +
ATP
ATP

15. Halo use bacteriorhodopsin (BR) to produce ATP using light energy
LIGHT PRESENT
LIGHT ABSENT
(DARK)
LIGHT
LIGHT
Bacteriorhodopsin
(BR)
Bacteriorhodopsin
(BR)
ADP
ADP + + P P
ATP
ATP

16. Halo use bacteriorhodopsin (BR) to produce ATP using light energy
LIGHT PRESENT
LIGHT ABSENT
(DARK)
LIGHT
LIGHT
Halobacterium cell
Halobacterium cell
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
Halo use BR to produce ATP for growth and metabolism
Halo cannot use BR to produce ATP

17. Halo change the expression of BR in response to the amount of light in their environment
Halobacterium cell
Bacteriorhodopsin (BR)

18. Halo change the expression of BR in response to the amount of light in their environment
Halobacterium cell
Bacteriorhodopsin (BR)

19. Halo change the expression of BR in response to the amount of light in their environment
LIGHT PRESENT
LIGHT ABSENT
(DARK)
LIGHT
LIGHT
Halobacterium cell
Halobacterium cell
When there is more light, halo respond by making more BR
When there is less light, halo make less BR

20. OUR QUESTION:
How do Halobacterium cells control the amount of BR expressed in response to light? What is the gene and protein network that regulates the expression of BR?