Scientists were somewhat surprised to discover that one of the fungi responsible for the disease known as “yeast” or “thrush,” Candida glabrata, engages in sexual reproduction. This is a bad thing for susceptible people, because the ability to mix genes could help the yeast cells develop resistance to treatment.
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Sexual reproduction could also make the glabrata more infectious, reported the team in Current Biology last week: The team led by Professor Toni Gabaldón of Barcelona notably found wide diversity in genes related to infectious ability.
Until now science thought the fungus, which makes sex anywhere from objectionable to painful for afflicted women, only reproduced asexually, by budding. Science had known that glabrata did have genes required for sexual reproduction, but science thought it just said no.
Most cases of vaginal candidiasis are caused by Candida albicans. The glabrata species was thought to be benign and to multiply asexually.
It’s not benign: glabrata is now thought to be the No. 2 culprit behind vaginal yeast infections, as well as infection of the urinary tract and other tissues. And it does exchange genes through the yeast version of sex.
The discovery of Candida glabrata’s sexual reproduction was based on sequencing 33 strains of the single-celled beast, and finding unexpected genetic diversity. Budding, i.e., cloning couldn’t explain that degree of diversity. The discovery of its sexual being was made by European scientists from the Université Paris-Sud in France, University Medical Centre Göttingen in Germany, and the Centre for Genomic Regulation in Barcelona.
Based on the genetic data, the team reconstructed a Candida glabrata family tree and concluded that once upon a time, there had been seven distinct types of it in different parts of the world. But as people started to travel, and mix and match, so did their little fungal stowaways.
It bears mention that the candida family of fungi can cause a range of human "Candidiasis" maladies, not only vaginal yeast infections. Infection of the mouth membranes is not rare, but the most dangerous form of infection is internal and systemic, when the fungi may attack almost any part of the body.
In separately upsetting news, the team suspects that Candida glabrata can live independently, not only as a parasite in or on the human body.
That new theory is based on the evidence of rapid evolution across different strains of glabrata, even in the same region. Microbes confined to a single organism (known as “obligate commensals”) tend to evolve in tandem with their host, and specific strains tend to be restricted to particular geographical areas. This wild proliferation suggests that glabrata also lives in the great wide world, though where – in soil, plant or other being - remains a mystery.