Secret sex life of killer fungus?

A team of scientists, led by researchers at The University of Nottingham, is studying the secret sex life of a fungus that causes potentially life-threatening infections in an effort to find new ways of controlling the disease.

Aspergillus fumigatus causes respiratory infection in up to 5,000 people per year in the UK alone and is also a major cause of respiratory allergy, implicated in asthma, affecting tens of thousands of people.

The fungus has always been thought to lack the ability to reproduce sexually, but new discoveries by the scientists led by Nottingham’s Dr Paul Dyer have shown that the fungus has a number of sexual characteristics, as reported in the current edition of the scientific journal Current Biology.

“The possible presence of sex in the species is highly significant as it affects the way we try and control disease,” said Dr Dyer.

“If the fungus does reproduce sexually as part of its life cycle, then it might evolve more rapidly to become resistant to anti-fungal drugs — sex might create new strains with increased ability to cause disease and infect humans”.

The team, which also includes lead researchers Mathieu Paoletti of The University of Nottingham, Carla Rydholm of Duke University in the US and David Denning of the University of Manchester, has used a number of techniques to study the fungus. Following the sequencing of the Aspergillus fumigatus genome, investigations have uncovered the presence of a series of genes needed for sexual reproduction.

Analysis of 290 specimens worldwide showed that fungus was composed of nearly equal proportions of two different sexes or ’mating types’, which in theory could have sex with each other. Further work on specific populations in America and Europe showed that genes were being exchanged between individuals of the fungus. Key genes involved with detecting mating partners were also found to be active in the fungus.

“Taken as a whole, the results indicate that the fungus has a recent evolutionary history of sexual activity and might still be having sex so far ’unseen’ by human eyes,” said Dr Dyer.

“The sexual cycle could be a useful genetic tool for scientists to study the way in which the fungus causes disease.”

He added: “The fungus is very common in compost heaps so these might be a hotbed of fungal sex!”

The study was funded by the Biotechnology and Biological Sciences Research Council, the Wellcome Trust and the Fungal Research Trust in the UK and Duke University in the US.