Deadly fungus gene code cracked

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Deadly fungus gene code cracked

Last Updated: Thursday, 22 December 2005, 00:16 GMT

Aspergillus fumigatus can be deadly

http://news.bbc.co.uk/1/hi/health/4546704.stm

Scientists have cracked the genetic code of a fungus responsible for

deadly infections and allergic reactions.

Aspergillus fumigatus, which causes more infections than any other

mould, is particularly dangerous to people with weakened immune

systems.

Researchers at the Institute for Genomic Research hope their work

could lead to better diagnostic tests, and treatments for fungal

infections.

Their international collaboration is reported in the journal Nature.

This study does for the first time start to give an indication of

why such closely related species in nature can have such different

effects

Dr Dyer

Experts believe that A. fumigatus has become an increasing threat in

recent years as more people with compromised immune systems are

surviving.

These include transplant patients, and people with leukaemia and

Aids.

The fungus also appears to trigger asthma in some people with

particularly sensitive immune systems.

It is unusual because it can thrive at a wide range of temperatures,

from 70 degrees Celsius - the temperature in a compost heap - to 37

degrees Celsius, inside the human body.

By altering ambient temperatures in the lab, scientists were able to

track how different genes were turned on and off as the environment

warmed.

The researchers discovered that the genome of the fungus is made up

of eight chromosomes bearing a total of almost 10,000 genes.

They found 700 genes that were either significantly different, or

did not occur at all in a similar, but less infectious fungus,

Neosartorya fischeri.

They also identified for the first time nine allergy-causing

substances produced by the fungus.

Knocking out genes

The researchers are now searching these unique genes for clues to

explain why A. fumigatus is so infectious.

The key genes are likely to play a complex role in the control of

many aspects of the way the fungal cells break down and construct

chemicals.

The plan is to systematically " knock out " or disable genes to find

out their individual effects.

Lead researcher Dr Nierman said: " This genome sequence is

going to be central for developing tools for effectively managing A.

fumigatus infections as they become more prevalent in the aging

population. "

Dr Dyer, an expert in fungi at the University of Nottingham,

said: " There is a lot of work ahead, and it is still early days.

" But this study does for the first time start to give an indication

of why such closely related species in nature can have such

different effects. "

Dr Dyer said A. fumigatus was incredibly abundant in the natural

world. It has been estimated that everybody inhales around 200

spores each day.

The researchers also decoded the genetic codes of two other species

of Aspergillus fungi.

They include A. oryzae, which has been used in the production of

foodstuffs such as soybean paste and soy sauce for 2,000 years.