Washington, Oct 31 : Scientists have found that tiny fungus, called microsporidia, that causes chronic diarrhea in AIDS patients, organ transplant recipients and travellers, is a member of the family of fungi that have been discovered to reproduce sexually.
The research team 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 of the study led by researchers at Duke University Medical Centre, 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," said Soo Chan Lee, Ph.D., lead author and a postdoctoral researcher in the Duke Department of Molecular Genetics and Microbiology.
He added: "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."
Using two genetic studies, the Duke scientists aimed 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.
Besides, both the 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.
Lee said that the findings suggested that microsporidia may have a genetically controlled sexual cycle, and may be undergoing sexual reproduction while they infect the host.
And the next step, according to him, 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.