Sex life of killer fungus finally revealed

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Sex life of killer fungus finally revealed

Science Centric | 30 November 2008 19:02 GMT

Science Centric - Sofia,Sofia Town,Bulgaria

http://www.sciencecentric.com/news/article.php?q=08113004-sex-life-

killer-fungus-finally-revealed

Biologists at The University of Nottingham and University College

Dublin have announced a major breakthrough in our understanding of

the sex life of a microscopic fungus which is a major cause of death

in immune deficient patients and also a cause of severe asthma.

The discovery of a sexual cycle in the fungal pathogen Aspergillus

fumigatus is highly significant in understanding the biology and

evolution of the species and will shed new light on its ability to

adapt to new environments and its resistance to antifungal drugs. It

is hoped the results of this research will lead to new ways of

controlling this deadly disease and improved treatments for patients

infected with it.

First described 145 years ago this killer fungus, until now, had no

known sexual cycle and was only thought to reproduce by production

of asexual spores. But researchers from the School of Biology at The

University of Nottingham and from University College Dublin, have

finally been able to induce sexual reproduction in this potentially

lethal pathogen showing, for the first time, that A. fumigatus

possesses a fully functional sexual reproductive cycle.

Dr Dyer is an expert in the sexual development and population

variation of fungi and co-author of 'Discovery of a sexual cycle in

the opportunistic fungal pathogen Aspergillus fumigatus,' which will

be published in Nature on 30 November 2008.

Dr Dyer said: 'This discovery is significant for providing both good

and bad news. The bad news is that we now know that Aspergillus

fumigatus can reproduce sexually, meaning that it is more likely to

become resistant to antifungal drugs in a shorter period, and the

sexual spores are better at surviving harsh environmental

conditions. The good news is that we can use the newly discovered

sexual cycle as a valuable tool in laboratory experiments to try to

work out how the fungus causes disease and triggers asthmatic

reactions. Once we understand the genetic basis of disease we can

then look forward to devising methods to control and overcome the

fungus.'

The spores of A. fumigatus, which feeds on dead or decaying organic

matter, are widespread in the atmosphere. It has been estimated that

everybody inhales around 200 spores each day. These spores are

normally eliminated by the innate immune response. However, this

fungus has become the most prevalent airborne fungal pathogen due to

its ability to cause infections in hosts with a weakened immune

system, with at least a 50 per cent mortality rate in humans. Four

per cent of patients in modern European teaching hospitals have

invasive aspergillosis; it is the leading infectious cause of death

in leukaemia and bone marrow transplant patients. The fungus is also

associated with severe asthma and sinusitis.

Almost one-fifth of all fungi have no known sexual stage - these

include many Aspergillus, Penicillium, Coccidioides and Malassezia

species which are of major economic and medical importance. However,

some of these species have apparently functional sex related genes

and this research could lead to a sexual revolution for many other

of these supposed 'asexuals.'

The research was carried out in collaboration with Dr Hubert Fuller

and his final year PhD student Celine O'Gorman from the UCD School

of Biology and Environmental Science at University College Dublin.

The study was funded by an IRCSET Postgraduate Research Scholarship,

an EC Marie Curie Training Fellowship and a grant from the British

Mycological Society, which facilitated research visits by Celine

O'Gorman to The University of Nottingham.

Many fungi reproduce by sexual means. The molecular-genetic and

physiological mechanisms controlling sex in fungi are being

investigated at The University of Nottingham with the aim of

devising new methods for the control of fungal diseases and

promoting sex in beneficial species. The consequences of sex for

genetic variation and evolution are being studied in model species

of fungi including plant pathogens and Antarctic lichen-forming

fungi.

Source: University of Nottingham