杏吧原创

IT鈥橲 hard to keep tabs on your bugs when you use them to munch up pollutants
in the soil鈥攁 technique known as bioremediation. Now researchers in the US
have conducted the first successful field trial of genetically modified bacteria
that glow as they work.

The bacteria, tested on an outdoor plot at the Oak Ridge National Laboratory
in Tennessee, did the job without escaping from the site. Nor did the
researchers find that the genes had spread from the modified bacteria to other
soil microbes. 鈥淚t鈥檚 the first release of a genetically engineered bacterium for
bioremediation authorised by the Environmental Protection Agency,鈥� says team
leader Gary Sayler of the University of Tennessee in Knoxville.

Sayler equipped a soil bacterium called Pseudomonas fluorescens HK44
with extra genes from soil-dwelling cousins that break down toxic hydrocarbons,
such as naphthalene. He also added lux, a gene that lets marine
bacteria glow bright yellow. Sayler and his colleagues then tested the bacteria
in soil contaminated with naphthalene and other hydrocarbons such as anthracene
and phenanthrene. The team prepared six samples of contaminated earth mixed with
engineered bacteria. Each sample was segregated in a cylinder 2.5 metres wide
and 4 metres high. These were buried in soil to a depth of 3 metres and linked
to an underground drainage system to keep an eye out for 鈥渆scapees鈥�.

At the start of the two-year trial, the engineered bacteria needed
kick-starting with some extra nutrients, but then multiplied, producing enough
of a glow for them to be detected with a hand-held light detector.

Sayler says that naphthalene levels decreased substantially in zones treated
with the engineered bacteria, but says it was difficult to tell how much
pollution was destroyed by natural microorganisms in the soil. Reassuringly, the
engineered bacteria appeared to stay put. Sayler says that hardly any were found
in the air above the soil and none were found in drainage water.

Environmentalists remain unimpressed. 鈥淚t鈥檚 a shame they didn鈥檛 use the
opportunity to look in more detail at gene transfer,鈥� says Sue Mayer of Gene
Watch, a British lobby group based in Buxton.