by Kenrick Vezina
Illustration by Yan Liang, via MIT News.
A team at MIT
has combined techniques from
synthetic biology and materials engineering to create hybrid “living materials”:
bacteria engineered to take up functional nanoparticles and grow into thin
layers with usable properties, like electrical conduction or light
emission. This achievement is a perfect follow-up to news from earlier
this month that another group at MIT had
successfully created bionic plants [Emphasis Others] (Read our Gene-ius post on the
Anne Trafton, writing for MIT
These “living materials” combine the advantages of live cells, which respond
to their environment, produce complex biological molecules, and span multiple
length scales, with the benefits of
nonliving materials, which add functions such as conducting electricity or
The organic analog of choice is bone. As Amina Kahn at the Los Angeles Times puts it:
Our bones are remarkable
feats of engineering; strong and yet light, shot through with holes and yet able
to bear incredible loads. This super-strong natural material is built as cells
incorporate hard minerals like calcium into living tissue.
The MIT team, led by assistant professor of electrical engineering and biological engineering Timothy Lu, was inspired by this interplay of living cells with nonliving components.
The process Lu and his team used begins with the bacteria E. coli and genetic engineering. They chose E. coli because it naturally produces thin, slimy films that adhere to surfaces — it’s this adhesion that’s key. In order to adhere to surfaces, E. coli produces “curli fibers”, comprised of repeating protein chains.
The MIT team replaced the bacteria’s ability to produce curli fibers with an engineered genetic circuit that only produces curli fibers if given a certain molecule. Now the team essentially has an on-off switch for the bacteria and can control the formation of biofilms: supply the bacteria with the trigger molecule and they produce curli fibers and form biofilms.
On top of this, the team engineered another set of E. coli with a
similar on-off switch but based on a different molecular trigger. And these
bacteria were modified one step further: researchers altered the genes coding for the creation
of curli fibers so that the protein chains would grab on to gold
So they had two
varieties of engineered bacteria, both controllable via distinct molecule of
their choosing, and one of the two’s ability to latch onto its environment
with curli fibers has been co-opted to make the bacteria gather tiny bits of
gold from its environment.
varieties, grow them together; manage their growth relative to one another
with the two on-off molecules; and supply some nanoscale bits of gold. The
researchers did just this and managed to coax the bacteria to build a tiny film
laced through with gold nanowires: a conductive surface comprised of living
And the conductive biofilm is just one of several proofs-of-concept
to come out of this project.
The team was also able to embed quantum dots — semiconductor nanoparticles that glow a particular color after being illuminated by light — in their biofilm through a similar technique.The final success lies in getting their modified cells to communicate with one another, as emphasized by the Christian Science Monitor. The molecular “on-off switches” described above don’t necessarily need to be supplied manually; in fact the researchers produced a third variety of E. coli which naturally produced the chemical trigger, activating the generation of gold-locking curli fibers in the second variety.
applications for these living
materials include batteries
and solar cells, diagnostic devices and scaffolds for tissue
engineering. According to Trafton, “The researchers are also interested
in coating the biofilms with enzymes that catalyze the breakdown of cellulose, which
could be useful for converting agricultural waste to
This latest breakthrough is sure to be one of many
similar efforts that blurs the
perceived boundaries between living and nonliving, artificial and
organic. We’re increasingly
able, as Lu and his team demonstrate, to manipulate our world at the level of
molecules and atoms — whether those are DNA molecules or gold
- “Engineers design ‘living materials’,” Anne Trafton | MIT News
- “Scientists build man-made ‘living-materials’ inside bacterial cells,” Amina Khan | LA Times
- “MIT scientists engineer ‘cells that talk to each other’,” Sudeshna Chowdhury | Christian Science Monitor
- “Synthesis and patterning of tunable multiscale materials with engineered cells,” Nature Materials
- “Bionic plants developed at MIT focus on the “tech” half of biotech,” Genetic Literacy Project (Anne Trafton | MIT News)
- “Living Materials Respond to the Environment and Communicate With Each Other,” Dexter Johnson | IEEE Spectrum
The article first appeared here.