ology is called “synthetic biology” [ 6].
Synthetic biology researchers try to
construct artificial systems by remodeling existing cells such as E. coli. The
difference between genetic engineering and synthetic biology may not be
immediately obvious. Genetic engineering essentially tries to add a single
function by inserting a gene into a cell.
Synthetic biology, on the other hand,
tries to add a system to a cell.
An illustrative example in synthetic
biology is the creation of a concentration band detector by Basu and his colleagues [ 1]. See Figures 1 and
implemented a system that included
a sensor to measure the concentration
of a specific substance in the outside
environment. The system then judges
whether the concentration is within a
This determination is made by a
genetic circuit consisting of several
genes. If the concentration is within
the range of interest, the green fluorescent protein (GFP) gene is expressed
and cells containing the gene glow.
The system consists of all three components: the sensor, computer, and
actuator, along with the GFP gene.
The system is implemented inside E.
coli cells. More specifically, a plasmid
(small chromosome) that contains the
necessary genes is inserted into E. coli
Synthetic biology clearly has a
close relationship with bioinformatics, which is already a mature research
field in which IT is used to analyze living organisms. It ranges from methods for analyzing genetic sequences
in genome chromosomes to those for
modeling and simulating biological
networks as complex systems. The latter approaches comprise the currently
active research field called systems biology, which tries to capture biological
phenomena from the point of systems
science. However, even systems biology focuses mainly on analyzing existing living organisms. In other words,
systems biology is a kind of reverse
engineering that tries to understand
natural systems inside cells, while synthetic biology is forward (i.e., ordinary)
engineering that tries to implement artificial systems in cells.
The purpose of synthetic biology
may not be clear. As noted above, input
Figure 1: The band-detect multicellular system programs
E.coli receiver cells to
fluoresce only at intermediate distances from sender cells. See Basu [ 1] for more.
Reprinted by permission from Macmillan Publishers Ltd: Nature [ 1], copyright 2005.
to and output from cells are usually
chemical substances. Therefore, by remodeling cells, the creation of useful
artificial systems that sense chemical
signals and produce chemical output
is possible. For example, one could
imagine bacteria that can search for
cancer by sensing signals from cancer
cells and destroying the cancer cells by
producing appropriate drugs.
DNA NANO TECHNOLOGY
Although making artificial systems out
of cells is nice, smaller systems that
could serve similar functions as those
of cells would be better. For example,
viruses are much smaller than cells but
are still capable of specific functions,
such as chromosome insertion. Therefore, nanotechnology researchers are
also focusing on constructing autono-