Biology Reference
In-Depth Information
which was indeed confirmed experimentally. Furthermore, the authors demonstrated that,
using this technology, they could construct multispecies biofilms consisting of
E. coli
with
either
B. subtilis
or
P. aeruginosa
. This study illustrates a powerful technique that may be very
useful in engineering complex biofilms.
ADVANCES IN TECHNOLOGY ALLOW THE PRECISE SPATIAL
ARRANGEMENT OF SYNTHETIC CONSORTIA
While the engineering of synthetic biofilms represents a tremendous feat in synthetic
biology, equally important are the technological advances that allow the rational design of
spatially structured, nonbiofilm-forming consortia. In 2008, Kim et al. created a synthetic
consortium that consisted of three wild-type strains of soil bacteria,
Azotobacter vinelandii
(Av),
Bacillus licheniformis
(Bl), and
Paenibacillus curdlanolyticus
(Pc).
40
Each strain performs a
different task that is vital for the survival of the entire population when grown in a selective
(contains penicillin) and nutrient-poor medium: Av fixes gaseous nitrogen into amino acids
using a molybdenum-requiring nitrogenase; Bl degrades penicillin G using
-lactamase
enzymes; and Pc generates a carbon source using cellulases to cleave carboxymethyl-
cellulose (
Fig. 13.4a
). Initially, the authors determined that, when cultured independently,
none of the strains grew in a nutrient-limited medium. When all three populations were
grown together as a well-mixed population, the consortium was not sustainable regardless
of the nutrient availability.
β
However, the authors predicted that spatial structure could allow all three populations to
grow together. To spatially separate the populations, the authors created a microfluidic
chamber that consisted of three physically separated culture wells that are joined through a
chemical communication chamber. When each population was seeded into a separate
253
(A)
Amino
acids
N
2
Av
CM
cellulose
Glucose
Pc
Penicillin
Bl
Communication channel
(B)
S. chlorophenolicum
Core shell
fiber
Well-mixed
Hg(II)
PCP
R. metallidurans
+ PCP
- PCP
Hg(II)
Hg(0)
- Hg(II)
- Hg(II)
FIGURE 13.4
The structure of a synthetic consortium modulates a novel behavior. (A) Spatial separation leads to a novel behavior. Three
bacterial populations were spatially arranged to allow them to cooperate in a selective (contains penicillin) and nutrient-poor
minimal medium.
40
The Av population converts gaseous nitrogen into amino acids. The Pc population converts CM-cellulose
into glucose while the Bl population degrades penicillin (
). When the three populations were well-mixed, the consortium did
not grow (top right panel). However, when the three populations are physically separated, but are allowed to communicate,
all three populations grow (bottom right panel). (B) Spatial orientation creates a novel behavior.
42
The bacterium S.
chlorophenolicum (green cells) can degrade PCP, but is inhibited by Hg(II). The bacterium R. metallidurans (red cells) can
convert Hg(II) into Hg(0). When these strains are grown in the presence of Hg(II) and PCP as a well-mixed consortium, Hg(II)
is converted to Hg(0), but PCP is not degraded (center panel). When spatially arranged in a core (S. chlorophenolicum)-shell
(R. metallidurans) fiber, Hg(II) is converted to Hg(0) and PCP is degraded.
