Tiny fungi may have sex while infecting humans

Oct 30, 2008

A fungus called microsporidia that causes chronic diarrhea in AIDS patients, organ transplant recipients and travelers has been identified as a member of the family of fungi that have been discovered to reproduce sexually. A team at Duke University Medical Center has proven that microsporidia are true fungi and that this species most likely undergoes a form of sexual reproduction during infection of humans and other host animals.

The findings could help develop effective treatments against these common global pathogens and may help explain their most virulent attacks.

"Microsporidian infections are hard to treat because until now we haven't known a lot about this common pathogen," says Soo Chan Lee, Ph.D., lead author and a postdoctoral researcher in the Duke Department of Molecular Genetics and Microbiology. "Up to 50 percent of AIDS patients have microsporidial infections and develop chronic diarrhea. These infections are also detected in patients with traveler's diarrhea, and also in children, organ transplant recipients and the elderly."

Of the 1200 species of microsporidia, more than a dozen infect humans. Their identity had been obscured because these tiny fungi cannot live outside of an infected host cell and they have a small number of genes which are rapidly evolving.

The Duke scientists used two genetic studies to show that microsporidia apparently evolved from sexual fungi and are closely related to the zygomycete fungus in particular.

They found that microsporidia share 33 genes out of 2,000 with zygomycetes. which the microsporidia did not share with other fungi. This genomic signature also shows that microsporidia and zygomycetes likely shared a common ancestor and are more distantly related to other known fungal lineages.

In addition, these two types of fungi have the same sex-locus genes – and in the same order – in their DNA. Other genes involved in sexual reproduction are also present. The findings suggest that microsporidia may have a genetically controlled sexual cycle, and may be undergoing sexual reproduction while they infect the host, Lee said.

Lee said the next step is to explore the sexual reproduction of these species, which may cause more severe (more virulent) infections because they use the host's cellular environment and machinery as a safe haven in which to reproduce.

"These studies resolve the enigma of the evolutionary origins and proper placement
of this highly successful group of pathogens, and provide better approaches to their experimental study," said senior author Joseph Heitman, M.D., Ph.D., director of the Center for Microbial Pathogenesis and director of the Duke University Program in Genetics and Genomics.

The team will pursue further studies with Duke genetic researchers Raphael Valdivia, Ph.D., and Alejandro Aballay, Ph.D., using cultured cells and C. elegans, a worm that researchers recently found is a natural host for microsporidia. "Using this roundworm may prove to be a useful way to study microsporidia genetics in a living creature," Heitman said.

Source: Duke University Medical Center

Explore further: Novel nanoparticle therapy promotes wound healing

add to favorites email to friend print save as pdf

Related Stories

Russian, American ready for a year in space

9 minutes ago

The Russian astronaut heading off for a year in space says he'll miss the natural landscapes on Earth. His American counterpart jokes he won't miss his twin brother.

Yahoo boosts share buyback plan by $2 billion

25 minutes ago

Yahoo on Thursday told US regulators that it will spend another $2 billion buying back shares as the pioneering US Internet search firm continues an effort to re-invent itself.

Flocks of starlings ride the wave to escape

4 hours ago

Why does it seem as if a dark band ripples through a flock of European starlings that are steering clear of a falcon or a hawk? It all lies in the birds' ability to quickly and repeatedly dip to one side to avoid being attacked. ...

Recommended for you

Novel nanoparticle therapy promotes wound healing

23 hours ago

An experimental therapy developed by researchers at Albert Einstein College of Medicine of Yeshiva University cut in half the time it takes to heal wounds compared to no treatment at all. Details of the therapy, ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.