How do algae respond to light?

Determining the Process of

Phototaxis in Chlamydomonas

reinhardtiiBy Kacie Capozzoli, Jenny Nguyen, and Chuck Thonsen

Background/Basis for Experiment

• Wild type Chlamydomonas reinhardtii move toward white light in the process of phototaxis, but the mutant strain does not.

• The inability of the mutant to perform phototaxis may be due to the eyespot being too small or weak, and unable to detect certain wavelengths of light.

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Determination of Spinach and Green Algae's Chloroplast Absorbance Spectra

Spinach

Chlamy-donas reinhardtii (Green al-gae)

Wavelengths

Ab

sorb

an

ce o

f C

hlo

rop

last

Su

s-p

en

sion

Specific Questions and Predictions

1. What caused the mutant strains of Chlamydomonas reinhardtii to be immotile and unable to perform phototaxis?

2. Would the eyespot of the mutant strain be able to detect blue light?

3. In presence of both white light and blue light, which type of light will the mutant strain go towards?

• Biological Prediction: The mutant strain will move towards the blue light, even when competing with the source of white light.

ResultsTRIAL 1: Phototaxis

 CC-125

(wildtype)CC-2894 (mutant)

control 0 0blue light 0 (++)white light 0 (++)

Physical appearance

control- no movement, blue and white light-

clumps, but minimal

movement towards the light

(ring)

control - clumps spread out and no movement, blue and white light- moving to light

TRIAL 2: Phototaxis  CC-125 (wildtype) CC-2894 (mutant)

control 0 0blue light 0 (++)white light + 0

Physical appearance

control- no movement, blue light- clumps, but

minimal movement to light, white light-

moving to light (very faint)

control- clumps spread out and no movement, blue

light- moving towards light, white light- clumps, but little movement

towards light (ring)

COMPETITION TRIAL 1  white light blue light

CC-125 (wildtype) 0 (++)CC-2894 (mutant) 0 0

Physical appearance

WT strain- minimal

movement towards light,

mutant strain- no movement

towards light

WT strain- moving towards light,

mutant strain- no movement

COMPETITION TRIAL 2  white light blue light

CC-125 (wildtype) 0 0CC-2894 (mutant) (++) (++)

Physical appearance

WT strain- no movement,

mutant strain- moving to light

WT strain- no movement,

mutant strain- moving to light