Synthetic biologists have been redesigning life for
decades now, but so far they’ve mostly been messing
about with single cells – a kind of souped-up version
of genetic modification. In 2010, Craig Venter and his
team created the first synthetic cell, based on a bug
that infects goats. Four years later, one of the first
products of the synthetic biology era hit the market,
when the drug company Sanofi started selling
malaria drugs made by re-engineered yeast cells.
Today, though, biologists are starting to find ways to
organise single cells into collectives capable of
performing simple tasks. They’re tiny machines, or as
biologist Josh Bongard at the University of Vermont
refers to them, ‘xenobots’. The idea is to ‘piggyback’ on
the hard work of nature, which has been building tiny
machines for billions of years.
Currently, Bongard’s team makes its xenobots with
ordinary skin and heart cells from frog embryos,
producing machines based on designs etched out on a
super-computer. Just by combining these two types of
cells it designed machines capable of crawling across
the bottom of a petri dish, pushing a small pellet
around and even cooperating. “If you build a bunch of
these xenobots and sprinkle the petri dish with
pellets, in some cases they act like little sheepdogs
and push these pellets into neat piles,” Bongard says.Their computer runs a simple evolutionary
algorithm that initially generates random designs and
rejects over 99% of them – selecting only those designs
capable of performing the required task in a virtual
version of a petri dish. As Bongard explains, the
scientists still have to turn the finished designs into
reality, layering and sculpting the cells by hand. This
part of the process could eventually be automated,
using 3D printing or techniques to manipulate cells
using electrical fields.
You couldn’t yet call these xenobots living
organisms, though, as they don’t, for example, eat or
reproduce. Since they can’t utilise food, they also ‘die’,
or at least decompose, and quickly, meaning there’s no
obvious hazard to the environment or people.
However, combining this approach with more
traditional synthetic biology techniques could lead to
the creation of new multicellular organisms capable
of performing complex tasks. For example, they could
act as biodegradable drug delivery machines, and if
made from human cells, they would also be
biocompatible, avoiding triggering adverse immune
reactions. But that’s not all. “In future work,” says
Bongard, “we’re looking at adding additional cell
types, maybe like nervous tissue, so these xenobots
would be able to think.”THE RISE OF LIVING MACHINES
Biological robots could start solving our problems3
AIautomatically designs candidate
lifeforms in simulation (top row), then
a cell-based construction toolkit is
used to create the living systems