Small but not so insignificant

2 July 2014

Neither animal nor plant. Yet not bacterial, archeal or fungal. Aphelids are an important parasitic microbe which has at long last been characterised.

A collaborative research effort between scientists from the School of Biological Sciences (Dr Frank Gleason and Dr Osu Lilje) and St. Petersburg State University and the Russian Academy of Science (Professor Sergey Karpov, Dr Maria Mamkaeva, Dr Vladimir Aleoshin and Dr Elena Nossova) has resulted in the characterisation of a new phylum of eukaryotic microorganisms, the Aphelida phyl. nov.

Species in three genera of this phylum are common parasites of phytoplankton in freshwater lakes and species in one genus are parasites of phytoplankton in the ocean. Several species of these microorganisms were studied in freshwater lakes in Russia by Dr Gromov over period of many years, but his published reports remained unnoticed until now. Dr Gromov considered that these parasites may play a role regulation of sizes of their host populations. Recently, similar species have been observed in populations of algae growing in ponds used for biofuel production in California and New Mexico, USA. The aphelid parasites may reduce the production of algae in these ponds.

Aphelid infection of five xanthophyte (yellow-green alga) cells. Photo by Professor Sergey Karpov.
Aphelid infection of five xanthophyte (yellow-green alga) cells. Photo by Professor Sergey Karpov.

In addition, the three phyla, the Aphelida phyl.nov., CryptomycotaandMicrosporidia have been reorganised by the collaborative research team into a new superphylum, the Opisthosporidia, which is sister to the true fungi or the Holomycota. This lineage includes many parasites of algal, fungal, amphibian, fish, and mammalian hosts. The species in the phyla, Aphelida, Cryptomycota and Microsporidia, are all obligate parasites, thus they are hidden within the host cells and are difficult to detect.

When asked about the significance of this work, Dr Lilje said that this was an important reorganisation of the range of microorganisms which sit evolutionarily between the animal and fungal kingdoms. "It is exciting to see these data published in the literature and the acknowledgement of the role of these non-bacterial microbes in ecology." The increasing recognition that these microbes are neither animal, plant, bacterial, archeal or fungal species will hopefully lead to a more holistic approach to understanding many of the ecological issues we are currently facing.