Thursday, September 4, 2014

A fungus for all seasons: causes dandruff in humans, but afflicts lobsters, sponges and corals as well

A fungus responsible for skin diseases in humans is also turning out to be common in the marine environment, and in combination with warming oceans is implicated in coral disease.

University of Hawai`i botanist Anthony Amend reported on the endlessly adaptable fungus Malassezia in the August 21, 2014, issue of the scientific journal PLOS Pathogens.

 It turns out the various species of Malassezia are everywhere, including some of the most inhospitable climates on the planet, from icy arctic soils to hot deep sea vents. That’s a far wider range of habitats than anyone had previously recognized. Until now, they have been understood as a land-based mammal problem.

It has been associated with dandruff, eczema and other human skin ailments, and it’s on seals as well. But Amend’s genetic studies of samples of diverse marine creature tissues show it has a much larger host population. It has now also linked to skin disease in lobsters, fish, plankton, and, yes, corals.

“Studies of fungi from environmental samples show that Malassezia are exceedingly widespread and ecologically diverse. Recent studies in little-characterized marine environments point to extensive diversification of Malassezia-like organisms, providing exciting opportunities to explore the ecology, evolution and diversity of this enigmatic group,” Amend wrote in the paper.

Bizarrely, a single strain has been found both in the arctic cold and in hydrothermal deep sea vents. 

“We have found multiple new examples of these fungi on corals, sponges and algae, and in water samples, deep sea thermal vents and sediments from Hawai‘i and around the world,” Amend said in a University of Hawai`i press release.

And the genetic work suggests the fungus repeatedly evolved from the marine environment to land and back again. The kinds that cause itching in humans are genetically intermediate between some of the marine species.

At Palmyra Atoll, to the south of Hawai`i, Amend found a tight link between Malassezia and a disease of coralline algae, which increased when water got warmer. That’s of interest to the Islands in a time of climate change, since coralline algae are a dominant builder of Hawai`i’s protective reef structures.

“A study of crustose coralline algae around Palmyra Atoll found that a Malassezia phylotype was abundant in banding disease lesions. Incidence of the disease increased by an order of magnitude following an el NiƱo event. A laboratory manipulation study showed that disease virulence correlated with an interaction between increases in CO2 and temperature,” the paper said.

It is not yet clear whether the fungus is the cause of the coral banding disease, or simply occupied a weakened reef.

“Analysis of environmental sequences demonstrates that putative members of the Malassezia lineage likely rank among the most widespread fungi on the planet,” Amend wrote. 

© Jan TenBruggencate 2014

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