A fungus that causes life-threatening infections in humans may be having sex, say scientists.
Aspergillus fumigatus, a fungus that has also been linked to asthma, had always been thought to reproduce asexually.
But a study by researchers at Nottingham and Manchester universities has revealed that the fungus has a series of genes required for sexual reproduction.
The discovery, published in the science journal Current Biology, has important implications for the way diseases caused by the fungus - estimated to affect some 5,000 people in the UK each year - are treated.
"The possible presence of sex in the species is highly significant as it affects the way we try and control disease," said Dr David Denning, of The University of Manchester.
"If the fungus does reproduce sexually as part of its life cycle, then it might evolve more rapidly to become resistant to antifungal drugs - sex might create new strains with increased ability to cause disease and infect humans."
The research team, headed by Dr Paul Dyer at the University of Nottingham, used a number of techniques to study the fungus's genetic make-up or genome.
The analysis of 290 specimens worldwide revealed that the fungus was composed of nearly equal proportions of two different sexes or 'mating types', which in theory could have sex with each other.
Further investigations, in Europe and America, showed that genes had been, or were being, exchanged between individuals of the fungus and that some key genes involved with detecting a partner were 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."
Further work is now aimed at seeing if the fungus can truly reproduce by sexual means.
Dr Dyer added: "The fungus is very common in compost heaps so these might be a hotbed of fungal sex!"
Source: University of Manchester. July 2005.