Radman said that a French company called Setratech hopes to use the
technique to incorporate extra genes into microorganisms, plants and animals,
to create hybrid species suitable for live vaccines, and to stabilise new
strains.

He and his colleagues, Christiane Rayssiguier in Paris and David Thaler
at the University of Utah, experimented with two bacteria, Escherichia coli
and Salmonella typhimurium (Nature, vol 342, p 396). These two bacteria
have a common ancestor, but have been separated for 150 million years and
the DNA in their genetic sequences differs by more than one-fifth. The researchers
managed to create a new ‘mosaic’ strain composed of genes from each species.
They did so by interfering with the mechanism by which cells that are about
to divide verify that their DNA has been copied faithfully.

A group of enzymes known as mismatch repair proteins are the key to
this process. The researchers reasoned that these enzymes might act as a
barrier to the recombination of genetic material from different species.

To test their prediction, they studied bacteria which have mutations
that made them unable to carry out this ‘repair’ routine. They found that
mutations in the mutL, mutS or mutH genes did indeed dramatically increase
the rate at which the two species of bacteria could exchange DNA, leading
to the ‘mosaic’ bacteria.

Radman says that he has now found a technique to inhibit the enzymes
in this system during the crucial period in the cell cycle of the two bacteria
when DNA is recombining. This opens the way, he says, for many practical
applications of this new approach to genetic engineering, in plant, animal
and human cells.

As a method of introducing new genes into cells, the procedure offers
several advantages. It is possible to obtain a large number of recombinant
cells, and a great variety of mutants, in a few hours. The method is protected
by a licence, and Setratech is now interested in forming partnerships with
other researchers in the field. It is negotiating joint ventures with industrial
partners that it declines to name at the moment.

‘The first practical applications are expected in two years’ time, in
fields such as yeast for fermentation, and agriculture and food,’ said Gilles
Amsallem of Setratech. The company’s research laboratory is in Paris, but
it also uses the premises and staff of the Jacques Monod Institute. Such
collaboration between industry and academia is rare in France, where basic
research does not often lead swiftly to the market.

Radman is continuing research into the ‘evolutionary’ consequences of
his work, and hopes to study the genetic mechanisms that separate two species.
He is searching for the ‘biological constant’ that determines the moment
when two species diverge and can no longer reproduce with one another.

Serge Dassault, head of the leading French fighter manufacturer, said
that in spite of the crash the Soviet Mig would be the main threat to his
company’s fighters in the marketplace. ‘This does not put any doubt on the
quality of the aircraft,’ says Dassault. ‘It will become one of our stiffest
³¦´Ç³¾±è±ð³Ù¾±³Ù´Ç°ù²õ.’

The Soviet display included the world’s largest aircraft, the Antonov
225, which has six jet engines and can carry 250 tonnes of cargo. It also
has computer controlled (‘fly-by-wire’) controls and a maximum speed of
850 kilometres per hour. It flew for the first time last December, but it
was shown for the first time in the West at this year’s show.

The Antonov can carry loads 80 metres long and 8 metres in diameter
on its back, such as parts for the giant Soviet booster rocket Energia or,
suggested the Soviet delegation, cracking towers for petroleum refineries.
The aircraft dramatically demonstrated its capabilities by arriving at the
show with the Soviet space shuttle on its back.

‘We anticipate using the Antonov-225 as a flying launch pad, to help
to put small rockets into orbit by allowing them to take off from its back,
at altitude,’ said Piotr Bulabuyev, head of the Antonov programme.

Orbital Science Corporation, a subsidiary of the American chemical company
Hercules, has also designed a mini-launcher for satellites based on a B-52
bomber. The first flight of the launcher, called Pegasus, is planned for
next August. The company hopes to sell the launcher in Europe through Arianspace,
the French commercial consortium that runs the European Space Agency’s launcher.
This week, the consortium signed a contract with Ball Aerospace Systems
of the US to design small communications satellites for Pegasus to carry.

The star of the Soviet display was the Sukhoi-27 intercepter, called
‘Flanker’. It, and a similar attack aircraft dubbed ‘Frogfoot’, visibly
impressed the aerospace engineers gathered at the show. The Su-27 intercepter
is 21 metres long, and rivals the capabilities of the best American fighter
aircraft, the F-15 Tomcat. It is thought to be the first Soviet fighter
capable of being completely controlled by computer. Experts at Le Bourget
said the Sukhoi is cheaper than the F-15.

One of the Sukhoi-27’s most notable features is a radar for guiding
missiles fired downward. This feature may have embarrassed the makers of
the British Tornado fighter who unveiled a similar radar at the air show
two years ago which failed to work. A similar radar has just recently been
developed for the new French fighter, Rafale.

Notable by its absence from the show was the companion to the Sukhoi
attacker and intercepter: the Sukhoi-24, a long-range bomber called ‘Fencer’.
It carries 8 tonnes of bombs amid its own 40 tonnes and can reach twice
the speed of sound. The bomber may have been withheld because of discussions
to limit long-range nuclear weapons now under way between the US and the
Soviet Union.