Table 1. Parameter estimates used in our model.

Parameter	Meaning	Estimated Value	Units
jc	Rate of active transport of 1,2-PD across the cell membrane	1 (when present) [22]	$\frac{cm}{s}$
$k_c^A$	Permeability of the Pdu MCP to propionaldehyde	10−5	$\frac{cm}{s}$
$k_c^P$	Permeability of the Pdu MCP to 1,2-PD	10−5	$\frac{cm}{s}$
Rb	Radius of the bacterial cell	5x10−5	cm
Rc	Radius of the Pdu MCP	10−5 [12]	cm
D	Diffusivity of metabolites in the cellular milieu	10−5 [37]	$\frac{c{m}^2}{s}$
$k_m^A$	Permeability of the cell membrane to propionaldehyde	10−3 [38]	$\frac{cm}{s}$
$k_m^P$	Permeability of the cell membrane to 1,2-PD	10−3 [39]	$\frac{cm}{s}$
kcatCDE	Maximum reaction rate of a PduCDE active site	3x102 [39]	$\frac{1}{s}$
NCDE	Number of PduCDE enzymes per cell	1.5x103 [12]	$\frac{1}{cell}$
KMCDE	Michaelis-Menten constant of PduCDE	5x102 [39]	μM
kcatPQ	Maximum reaction rate of a PduPQE active site	55 [16]	$\frac{1}{s}$
KMPQ	Michaelis-Menten constant of PduPQ	1.5x104 [16]	μM
NPQ	Number of PduPQ enzymes per cell	2.5x103 [12]	$\frac{1}{cell}$
Pout	External 1,2-PD concentration	5.5x104 [21]	μM
Aout	External propionaldehyde concentration	0 [21]	μM