Beware--Money Hungry Scientists Playing God with Deadly Bacteria

News Feature

Nature 431, 624 - 626 (07 October 2004); doi:10.1038/431624a
http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v431/n7009/f
ull/431624a_fs.html

Synthetic biology: Starting from scratch

Genetic engineering is old hat. Biologists are now synthesizing genomes,
altering the genetic code and contemplating new life forms. Is it time to
think about the risks? Philip Ball asks the experts.

Redesigning Life. That was what Steven Benner wanted to call his 1988
conference in Interlaken, Switzerland. A chemist now at the University of
Florida in Gainesville, Benner was organizing the meeting to explore the
possibilities for making artificial chemical systems that mimic essential
features of living things.

But his title caused such a furore among prospective attendees that Benner
had to tone it down to Redesigning the Molecules of Life. "Individuals as
distinguished as Nobel laureates were convinced that the title would incite
anti-recombinant-DNA riots in Switzerland," Benner explains.

Benner's conference helped to define one strand of the emerging discipline
known as synthetic biology, a field that is now raising worries that won't
be deflected simply by semantics. The expanding toolbox of ways to
re-engineer microbes < and even construct new ones < has opened up
extraordinary possibilities for biomedical discovery and environmental
engineering. But it also carries potential dangers that could eclipse the
concerns already raised about genetic engineering and
nanotechnology. If biologists are indeed on the threshold of synthesizing
new life forms, the scope for abuse or inadvertent disaster could be huge.

In a dramatic demonstration of the potential risks, virologist Eckard Wimmer
at the State University of New York at Stony Brook announced in 2002 that
his team had built live poliovirus from scratch using mail-order segments of
DNA and a viral genome map that is freely available on the Internet1. The
feat put a spotlight on the possibility that bioterrorists could create even
more dangerous organisms < including Ebola, smallpox and anthrax < perhaps
endowing them with resistance to
antibiotics.

Creative thoughts

Since then, biologists' abilities to engineer life have bounded ahead.
Wimmer took three years to build his poliovirus, but last November genome
sequencer Craig Venter and his colleagues at the Institute for Biological
Energy Alternatives in Rockville, Maryland, announced that they had taken
just three weeks to assemble a virus that infects bacteria2. At the same
time, bacterial cells are being rewired to perform functions they can't
fulfil in nature. And researchers are getting close to determining the
smallest set of genes necessary to support a living cell, which might make
it possible to cook up new life forms.

Almost 30 years ago, concerns that recombinant DNA technology could pose
risks to human health and the environment prompted leading molecular
biologists to call an unprecedented summit. They gathered at the Asilomar
Conference Center in Pacific Grove, California, in February 1975, where they
decided to voluntarily forego some kinds of research and to instigate safety
measures to prevent abuses of the new techniques.

Is it now time for another Asilomar? Researchers involved in synthetic
biology generally agree that more discussion of how to avoid risks is
urgently needed, but have yet to take the formal step of calling for a
summit. Some concerns were aired at a
special session at the First International Meeting on Synthetic Biology,
held in June at the Massachusetts Institute of Technology (MIT) in
Cambridge, but it did not set out to produce policy recommendations.

The reason we face the question of risk at all is that the potential rewards
of pursuing synthetic biology are so great. Protein engineer Wendell Lim of
the University of California, San Francisco, says that if synthetic biology
is successful, it may become possible to treat a variety of diseases by
repairing defective cell functions, targeting tumours or stimulating growth
and regeneration of specific cell types. Other researchers are hoping to
engineer bacteria to make complicated drugs or to use sunlight to generate
clean-burning hydrogen for cars and power plants.

Synthetic biology is the logical corollary of the realization that cells,
like mechanical or electronic devices, are exquisitely 'designed' < albeit
by evolution rather than on the drawing board. Their functions are enacted
by circuits of interacting genes. As scientists began to map these circuits
in the 1990s, they inevitably began to wonder whether they could rewire
them.

Glowing report

In 2000, biological physicists Michael Elowitz and Stanislas Leibler, both
then working at Princeton University in New Jersey, designed from scratch a
genetic circuit that caused oscillating production of a fluorescent protein.
Bacteria programmed with
the circuit glowed periodically3. Other researchers built on this, creating
circuits that could be switched on and off by external signals, or that
could control bacterial population density4, 5.

Now a growing number of researchers are working on ways to alter the
circuitry of cells. Lim, for instance, is retooling some of the proteins
that carry signals within and between cells so that they respond to
different inputs from the environment6, 7. And chemical engineer Jay
Keasling at the Lawrence Berkeley National Laboratory, has refitted the gut
bacterium Escherichia coli with the circuitry it needs to synthesize a
precursor to the powerful antimalarial drug artemisinin, a product of the
wormwood plant that is currently too expensive for widespread use. This
meant importing ten genes from other organisms, including wormwood and
brewer's yeast, and then carefully tuning their expression levels8. If this
proves to be a cheap, reliable source of the drug, it could transform the
treatment of malaria.

In a parallel development, other researchers have been tinkering with the
building blocks of genes and proteins themselves. Naturally occurring
proteins are built from a standard set of 20 amino acids. Although these are
enough to produce protein
chains with a staggering array of functions, expanding this repertoire might
enable the design of biomolecules with new functions, such as protein-based
drugs that resist being broken down in cells.

In 1989, Peter Schultz, a chemist now at the Scripps Research Institute in
La Jolla, California, reported that he had found a way to persuade bacteria
to incorporate an unnatural amino acid into a specific protein9. This
produced enzymes with subtly different activities. Since then, Schultz has
added more than 80 unconventional amino acids to proteins.

Culture shock

In the same year, Benner persuaded cells to insert a base pair not used in
nature into their DNA10. A better understanding of the different types of
molecules that can function as DNA bases will open a window to the possible
chemical ancestors of DNA that might have existed on primordial Earth, and
to the possible genetic systems that could support life on other worlds. "I
suspect that, in five years or so, the artificial genetic systems that we
have developed will be supporting an artificial life form that can
reproduce, evolve, learn and respond to environmental change," Benner
predicts. "This will help define how life not of earthly origin might
appear."

As biologists learn to shape cellular circuits and their molecular
components, developments in the automated chemical synthesis of DNA are
allowing entire genomes to be designed and assembled. Venter's
lightning-fast synthesis of a virus in November was a testament to the
expanding capacity of DNA synthesis machines. By some estimates, next year's
machines will be able to generate sequences about a million base pairs long
< roughly the size of the genome of Chlamydia, which causes a common
sexually transmitted disease, and a quarter the size of E. coli's genome.

"Bacterial genomes are within the range of current DNA-synthesis
technology," says John Mulligan, president of the DNA-synthesizing company
Blue Heron Technology in Bothell, Washington. But bacterial genomes must be
embedded within a cell and its attendant biochemical machinery, making them
much harder to synthesize than viruses. Nevertheless, attempts are under
way. In November 2002, Venter made a high-profile announcement of his
intention to build a simple bacterium starting with machine-made DNA.

Plain and simple

But building a new bacterial genome is not just a matter of chemistry < you
have to design the circuitry too. That's the hard part, so it's good to
simplify. "An alternative to understanding complexity is to get rid of it,"
says Tom Knight, a computer scientist at MIT who brings an engineer's
perspective to synthetic biology.

To this end, Knight is studying one of the simplest organisms known,
Mesoplasma florum, a bacterium that has only 682 genes. The draft genome of
this organism was completed last year, and its metabolic pathway has been
mapped. The 793-kilobase genome seems to contain very little non-essential
DNA, but Knight thinks it can be simplified further. He is now mapping its
circuitry and modelling it on a computer to see what else can be removed.

All of these technologies combined are raising issues similar to those that
sparked the Asilomar summit. Back then, molecular biologists realized they
had all the tools to genetically modify bacteria < and possibly higher
organisms < in just about any way imaginable. The hope was that bacteria
could be engineered to produce drugs such as human insulin cheaply, and
indeed they soon were. The worry was that no one knew how modified bacteria
might fare in the environment < whether,
for example, they might be toxic, or resistant to antibiotics.

Synthetic biology is now raising the bar. Should limits be set on what is
attempted? If so, what should they be and how should they be enforced? And
what steps can be taken to ensure that a rogue organization, or even a
state-sponsored bioweapons
programme, does not use the technology to synthesize a dangerous microbe?

Roger Brent, president of the Molecular Sciences Institute in Berkeley,
California, suggests that one option might be for DNA synthesis to require a
licence. But more importantly, Brent says, synthetic biology should avoid
developing a hacker
subculture like that which spawns computer viruses. Rogue computer hackers
hope to earn respect from their peers by producing particularly clever or
insidious virus programs. Brent urges researchers in the field to encourage
responsible lab culture by not engaging in showy stunts with no research
purpose.

Assembly lines

Even though licensing is currently not required, some DNA synthesis
companies have taken their own steps to avoid inadvertently aiding
irresponsible work. Molly Hoult, senior vice-president of Blue Heron, says
that all the company's orders for DNA are cross-checked against a database
of "biological nasties". If a match turns up, the company tries to find out
more about the customer's research before completing the order. If it can't
easily be checked out, Blue Heron simply turns the order down. "We walk away
from some business," Hoult says.

Such self-policing could become the norm, and scientists might even be asked
to cooperate more closely with intelligence agencies to prevent the abuse of
synthetic biology. An unclassified report by the CIA released last November
warned that synthetic biology could produce engineered agents "worse than
any disease known to man" and suggested "a qualitatively different working
relationship between the intelligence and biological sciences communities".
In particular, the bioscience community might function as a "living sensor
web" that reports to the government on technical advances that could be used
as weapons11.

But it is not clear whether the risk of bioterrorism will be the most
important concern with synthetic biology. Ron Weiss, an electrical engineer
at Princeton University who spends his time rewiring bacteria, points out
that adding antibiotic-resistance genes to harmful bacteria is relatively
straightforward and has been possible in principle since the 1970s < yet it
has not become a major focus of biowarfare. It would be easier and cheaper
simply to breed and release existing harmful organisms than to make new
ones. "If I was a terrorist," says Weiss, "this isn't the way I'd get
maximal damage for my buck."

It is much harder to anticipate the unintentional dangers of synthetic
biology. For example, if new strains of bacteria were developed with
unprecedented capabilities, how could they be kept under control?

One way might be to use built-in safeguards. For instance, the innate
ability of bacteria to respond to high population density, a feature known
as quorum sensing, could be co-opted to activate a self-destruct mechanism.
Another option might be to build gene circuits that function like the logic
gates of computers to count the number of times a cell divides. After a
preset number, the cell would die.

Initial attempts have been made. Unfortunately, Weiss has found that mutant
strains evolve after just a few days that can evade his population-control
mechanism5. But he thinks this can be solved by creating several layers of
defence. After all, such redundancy seems to be built into naturally
occurring quorum-sensing bacteria, which do not mutate to evade their own
population controls. "Nature does this already," Weiss says.

Into the unknown

Yet as synthetic biology develops, it will be hard to anticipate all the
possible problems, whether malevolent or inadvertent. "The repertoire over
the coming decade is limitless," says George Poste, a bioterrorism expert
and director of the Biodesign
Institute at Arizona State University in Tempe. "You'll never identify all
the risks." Poste says that he is not particularly concerned about immediate
dangers, as most researchers are still working with biological materials
isolated from cells, so nothing is likely to escape from the laboratory. But
"fast-forward two decades and it may be quite different", he adds.

To help quantify risks as they emerge, Poste proposes developing what he
calls a 'calculus of risk' < an equation that can enumerate a 'risk factor'
for new developments and sound an alarm bell when a certain risk threshold
is reached. It's a necessarily crude tool < Poste's equation includes poorly
quantified factors such as the projected time it would take to convert a new
technology for malevolent use < but it might at least help to distinguish
remote risks from more immediate ones.

The difficulty of putting a finger on the risks might leave researchers
attending an Asilomar-style conference clutching at shadows. So for now the
talks will remain informal. "This definitely merits a lot more discussion,"
says Weiss. "We don't
understand the issues sufficiently yet."

Sooner or later, synthetic biology may find itself facing dangers that are
far more than hypothetical. As Poste puts it: "Biology is poised to lose its
innocence."

PHILIP BALL
Philip Ball is a consultant editor of Nature.

References
1.Cello, J., Paul, A. V. & Wimmer, E. Science 297, 1016­1018 (2002). |
Article | PubMed | ChemPort |
2.Smith, H. O., Hutchison, C. A., Pfannkoch, C. & Venter, J. C. Proc. Natl
Acad. Sci. USA 100, 15440­15445 (2003). | Article | PubMed | ChemPort |
3.Elowitz, M. B. & Leibler, S. Nature 403, 335­338 (2000). | Article |
PubMed | ChemPort |
4.Gardner, T. S., Cantor, C. R. & Collins, J. J. Nature 403, 339­342 (2000).
| Article | PubMed | ChemPort |
5.You, L., Cox, R. S., Weiss, R. & Arnold, F. H. Nature 428, 868­871 (2004).
| Article | PubMed | ChemPort |
6.Dueber, J. E., Yeh, B. J., Chak, K. & Lim, W. A. Science 301, 1904­1908
(2003). | Article | PubMed | ChemPort |
7.Park, S. -H., Zarrinpar, A. & Lim, W. A. Science 299, 1061­1064 (2003). |
Article | PubMed | ChemPort |
8.Martin, V. J. J., Pitera, D. J., Withers, S. T., Newman, J. D. & Keasling,
J. D. Nature Biotechnol. 21, 796­802 (2003). | Article | PubMed | ChemPort |
9.Noren, C. J., Anthony-Cahill, S. J., Griffith, M. C. & Schultz, P. G.
Science 244, 182­188 (1989). | PubMed | ChemPort |
10.Switzer, C., Moroney, S. E. & Benner, S. A. J. Am. Chem. Soc. 111,
8322­8323 (1989). | ChemPort |
11. The Darker Bioweapons Future (Office of Transnational Issues, CIA, OTI
SF 2003-108, 2001); http://www.fas.org/irp/cia/product/bw1103.pdf

****************************************************************************
*****************************
This GMO news service is underwritten by a generous grant from the Newman's
Own Foundation and is a production of the Ecological Farming Association
www.eco-farm.org <http://www.eco-farm.org/>
****************************************************************************
*****************************