Professor Anthony Amend from the University of Hawaii at Manoa showed very recently that the fungus genus Malassezia is not only found on human skin with conditions such as dandruff and eczema, but has also been identified in marine environments such as deep-sea sediment, hydrothermal vents, corals, guts of lobster larvae, eel tissue, and Antarctica soils.
More remarkably, sequencing and tree building of species relatedness shows that the marine species and terrestrial (non-marine) species do not group together but “interdigitate”, or are spread randomly in the way they group together in their relatedness. The evidence suggests that the marine and terrestrial forms have jumped repeatedly between habitats.
The data was obtained from a number of sources, most of them “environmental sequencing” projects around the world which aim to do simultaneous sequencing of all DNA found in a sample. Done correctly the analysis yields in one try the identities of all organisms captured in a sample.
Prior to this analysis, it was thought that these fungus evolved to become optimally suited to mammalian skin. But the careful analysis of environmental sequencing efforts overturned that belief. One species could be spread out all over the globe, on land as well as in ocean. One example is Malassezia restricta, found on human skin but also in extreme habitats such as arctic soil and hydrothermal vents.
Marine animals also carry this fungus, including higher order seals and lower order fish, lobsters, and corals.
One criticism is that sequencing is bound to become contaminated especially with a fungus endemic to human skin. However, the detection of completely novel species make contamination a much less likely correct explanation. And moreover, RNA is a fairly unstable molecule, so in the cases where detection occurred for some of the samples in which there was sufficient time for degradation suggests that microbes were actively generating RNA.
While it is associated with many skin conditions it is unclear as of yet whether the fungus is a causal factor. This is simply because disease etiology is a complex interplay of an individual immune system and disease agent.
Likewise the significance of the genus and its species in marine environments is as yet unclear. Coral algae have been observed to host a Malassezia type fungus in lesions during outbreak of banding disease. But further attempts to isolate and cultivate the fungus were unsuccessful so it was never clear whether the fungus was a causal factor or the result of disease.
The research was published on Aug 21, 2014 in PLoS Pathogens.