Density Dependent Bioluminescence
free
living, 10 cells/liter
<0.8
photons/second/cell
symbiotic, 1010 cells/liter
800 photons/second/cell
Ø A positive feedback circuit
luxR
luxI
luxC
luxD
luxA
luxB
luxE
luxG
LuxR
LuxI
P
P
Low Cell
Density
O
O
O
O
N
H
luxR
luxI
luxC
luxD
luxA
luxB
luxE
luxG
LuxR
LuxI
(Light)
hv
Luciferase
P
P
High Cell
Density
LuxR
O
O
O
O
N
H
O
O
O
O
N
H
O
O
O
O
N
H
O
O
O
O
N
H
LuxR
(+)
O
O
O
O
N
H
O
O
O
O
N
H
O
O
O
O
N
H
O
O
O
O
N
H
O
O
O
O
N
H
O
O
O
O
N
H
O
O
O
O
N
H
O
O
O
O
N
H
O
O
O
O
N
H
O
O
O
O
N
H
O
O
O
O
N
H
O
O
O
O
N
H