'Suicide germ' may ease mutation fears

PUBLISHED : Sunday, 19 July, 2009, 12:00am
UPDATED : Sunday, 19 July, 2009, 12:00am

Mainland scientists hope a new 'suicide germ' will allay fears of dangerous mutations from genetically engineered micro-organisms (GEMs) released into the environment.

They have developed a biological system that triggers the 'suicide' of GEMs, which can be effective in cleaning up environmental contamination such as oil spills and pesticide residues, but their application has been limited because of mutation concerns. And there are other potential applications such as more sophisticated biological weapons.

'One way to reduce the potential risk of genetically-engineered micro-organisms to the environment is to use a containment system that does not interfere with the performance of the germ until activated,' said Wu Yijun , lead researcher and a professor at the Institute of Zoology in the Chinese Academy of Sciences.

Professor Wu and his team from the Laboratory of Molecular Toxicology created an active biological containment system in a GEM that glows in the dark, breaks down pesticide residue on vegetables and selfdestructs when its job is done.

'We used E. coli [a usually harmless germ commonly found in human intestines] to host an alien gene. There was some natural resistance from the host ... we spent many hours in the lab working on the E. coli, trying different ways to persuade the bacteria to become a GEM. They co-operated in the end.'

The containment trigger is like a 'suicide cassette' that is implanted in the GEM, and the self-destruct, or suicide, trigger can either be the presence of a chemical or environmental signal such as temperature.

'When the triggering scenario occurs, the gene will convert normal materials in its body into poison, killing itself instantly,' Professor Wu said. 'The triggering mechanism can be tailored to meet the demand of consumers. For instance, you could set 40 degrees Celsius as a trigger. When the temperature exceeds the programmed level, all bacteria will die.

'Or you can choose a chemical. Even the slightest change in salt levels in water can start the termination process.'

The scientists used nanotechnology, which has been applied in areas from breaking down trash and brewing beer to killing pests and generating biogas. The ability to control GEMs could make them safer and more efficient.

Professor Wu said the containment technology could also be applied to bioweapons, for example, in Clostridium botalinum, which is potentially the most powerful toxin.

'Before the Olympics, all labs in Beijing received instructions from the government to eliminate all Clostridium botalinum samples. If the self-destructing device is put in the germ, we may not have to worry so much about it.'

US researchers in the late 1980s proposed the idea of a self-destructing micro-organism, but scientists had difficulty turning theory into reality. The mainland is a latecomer to the field, but is fast catching up.

'Some developed countries, including the United States, have put a lot of resources into this technology. Scientists around the world are working hard to produce various kinds of self-destructing micro-organisms. It is a race,' Professor Wu said.

The professor said there were still hurdles to overcome in the 'suicide cassette'.

'There are still a few problems that need to be worked out before its mass application. For example, man-made micro-organisms can mutate once released into nature. We are still unable to fully predict the outcome.'

Gao Meiying , applied microbiology researcher at the Wuhan Institute of Virology under the Chinese Academy of Sciences, said that although the research had profound implications, the potential for a biological disaster was also frightening.

'Taking the life and death of a micro-organism into our hands is a bit like playing God,' said Professor Gao, who was not a member of the research team.

'We will have an unlimited supply of microscopic soldiers and workers to do the deadly and filthy work while keeping the situation under control.

'But if one day, people feel confident enough about the technology and take it out of the lab, I'll be against it. A germ that behaves like an angel in the lab can be a demon in nature.'

The research paper was published in the latest issue of the Applied Microbiology and Biotechnology journal.

The mainland is making rapid strides in the field of genetic engineering. Even though it may not be a new discovery, scientists last month found a strain of bacteria that has the potential to be used to clean up oil spills.


Modifying genetically-engineered micro-organisms so they commit suicide when their job is done should ease concerns about releasing them into nature

How it works

1 A genetically engineered micro- organism (GEM) is given a 'suicide cassette', a containment system which doesn't interfere with the GEM until activated

2 The GEM containing the cassette is cultivated in a laboratory and multiplies

3 The modified GEMs are released into nature to perform a specific task, such as remove pesticide residue from vegetables, and they continue propagating while on the job

4 Once their job is done, the GEMs are induced to commit suicide by introducing an environmental signal, such as spraying salt water