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Last Updated: Thursday, 22 December 2005, 00:16 GMT
Deadly fungus gene code cracked
Aspergillus fumigatus
Aspergillus fumigatus can be deadly
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 Paul 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 70C - the temperature in a compost heap - to 37C, 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, including scientists from the UK's Wellcome Trust Sanger Institute, 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 William 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 Paul Dyer, an expert in fungi at the University of Nottingham, UK, 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 sequenced 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.

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