BIO 93 Lecture 13 - M122 - Microbial
Evolution and Bacterial Diversity Exam
Questions and Answers with Verified
Solutions | Latest Updated 2026
, Quorum Sensing Input: cell density
Output: makes light (or other things)
sensing ones self - allows bacterial cells to
work
together at high density.
Quorum Sensing → Light Production
(Simple
Steps)
Step 1: Each bacterium makes a signal
molecule.
This small molecule is called an
autoinducer.
Step 2: At low cell density, the signal
spreads out.
There aren’t many bacteria, so the signal
doesn’t
build up. ➡■ No light is produced.
Step 3: As bacteria multiply, more signal is
made.
Now there are many bacteria producing
autoinducer.
Step 4: Signal concentration reaches a
threshold.
When enough signal builds up, it binds to a
regulatory protein.
Step 5: Light genes turn ON. The bacteria
activate
the luciferase gene.
Step 6: The bacteria glow. All the bacteria
produce
light together.
Evolution and Bacterial Diversity Exam
Questions and Answers with Verified
Solutions | Latest Updated 2026
, Quorum Sensing Input: cell density
Output: makes light (or other things)
sensing ones self - allows bacterial cells to
work
together at high density.
Quorum Sensing → Light Production
(Simple
Steps)
Step 1: Each bacterium makes a signal
molecule.
This small molecule is called an
autoinducer.
Step 2: At low cell density, the signal
spreads out.
There aren’t many bacteria, so the signal
doesn’t
build up. ➡■ No light is produced.
Step 3: As bacteria multiply, more signal is
made.
Now there are many bacteria producing
autoinducer.
Step 4: Signal concentration reaches a
threshold.
When enough signal builds up, it binds to a
regulatory protein.
Step 5: Light genes turn ON. The bacteria
activate
the luciferase gene.
Step 6: The bacteria glow. All the bacteria
produce
light together.
