Question

experiment: part 3
in the third part of the experiment, dr. bassler performed the same experimental procedure as before, but she used both strain a and strain b. she divided the culture plate into halves and labeled one side \a\ and one side \b.\ she then spread a small amount of strain a on one side and strain b on the other side using an inoculation loop. the culture dish was then placed into an incubator for 24 hours before being analyzed for bioluminescence.

1. after incubation do you predict the researchers will see bioluminescence? why or why not?

yes they will see bioluminescence in here are receptors and signal molecules

1. using the petri dish to the right, shade in the sides you predict to see bioluminescence. if you do not predict any bioluminescence then leave the side(s) blank.

drawing conclusions

1. for each part of the experiment (1-3) provide a brief explanation justifying your predictions of bioluminescence on the culture plates. (hint: refer back to the information found in figure 2)
2. only a (no bioluminescence) no receptors for signal molecules
3. only b (no bioluminescence) no signal molecules for receptors
4. a and b (bioluminescence) interactions in middle causes bioluminescence
5. how do the results of this experiment demonstrate communication between bacterial cells?

Explanation:

For Question 1 (Prediction of Bioluminescence):

This experiment involves bacterial quorum sensing, where strain A produces signal molecules and strain B has receptors for those signals. When both are present, the signal molecules from A bind to B's receptors, triggering bioluminescence.

For Question 2 (Shading the Petri Dish):

Bioluminescence occurs where the two strains interact, so the middle region between sides A and B should be shaded, along with adjacent areas of A and B where signal-receptor binding happens.

For Drawing Conclusions 1:

1. Only strain A: No receptors to detect signals, so no bioluminescence.
2. Only strain B: No signal molecules to activate receptors, so no bioluminescence.
3. Strains A and B: Signal molecules from A bind to receptors on B, triggering the bioluminescent response in the overlapping/interacting region.

For Drawing Conclusions 2:

The results show that bioluminescence only occurs when both strains are present. Strain A sends chemical signals, and strain A receives/responds to them, proving bacterial cells communicate via chemical signal molecules to trigger a collective response (bioluminescence).

Answer:

1. Yes, they will see bioluminescence. Strain A produces signal molecules, strain B has matching receptors; their interaction triggers the response.
2. (Shade the middle overlapping region of the petri dish between side A and side B, plus the inner edges of A and B adjacent to this middle area)

Drawing Conclusions 1:

1. Only A: No bioluminescence, no receptors for signals.
2. Only B: No bioluminescence, no signal molecules.
3. A and B: Bioluminescence, signal-receptor interaction triggers it.

Drawing Conclusions 2:

Bioluminescence only occurs when both strains are combined, showing strain A releases chemical signals that strain B detects and responds to, demonstrating bacterial intercellular communication via chemical signaling.