PhytomyxID: Diversity, abundance of Phytomyxids

Phytomyxids are protozoan parasites of plants, algae, and oomycetes. Their obligate relationship with their hosts has hampered research on this group. Only a few species are well known, principally those causing economically important plant diseases like clubroot in brassicas, powdery scab of potatoes, and those acting as vectors for plant viruses. Recent work suggests that there is a much higher diversity of unknown phytomyxids in a wide range of habitats, and that the range of host species is significantly greater than known. Drs Neuhauser and Bass have independently produced highly suggestive new data on phytomyxids and their relatives, the development of which forms the scientific bases of this project. Aims of this study are to produce first qualitative and quantitative data that will allow to estimate the "true" biodiversity of phytomyxids in key environments (marine, freshwater and terrestrial) where this group of microorganisms has been so far undersampled. The results from the first phase of our work (general and directed DNA-based environmental probing, in combination with information extracted from existing pyrosequencing datasets) will form the basis for a more targeted second phase, a more lineage-specific probing using RNA-based approaches, microscopy, and microcosms. The detected taxa will be linked to their host species using contemporary microscopy techniques (e.g. confocal, FISH, fluorescence) and - where suitable - bait tests to study and describe the complete phytomyxid life cycle. The combination of these contemporary approaches will result in the most comprehensive study of this group of enigmatic parasitic protists. Key research outputs will be: 1. A revolutionary increase in knowledge of the biodiversity and phylogenetic relationships of phytomyxids and their relatives. 2. Increased knowledge of the ecological distribution and activity of phytomyxids in diverse habitats and in association with a wide range of potential hosts and environments. 3. The adaptation and development of integrated tools for the identification, detection, and monitoring of phytomyxids, including fluorescence and confocal microscopy, DNA- and RNA-based environmental probing techniques, and quantitative PCR. 4. Improved bioinformatics methods for mining and analysing group-specific data from 454-sequencing libraries. Thus we will open up new research avenues in the detection, monitoring, and characterisation of phytomyxids and their relatives that will in the long run result in a much deeper insight into the impact of phytomyxids on key ecosystem processes like food web dynamics, host community establishment and stability, and new insight into possible control of plant diseases caused by phytomyxids.

Phytomyxids are largely elusive group of microbial pathogens of a wide range of hosts with only a couple of species that are well studied (e.g. clubroot). During PhytomyxID we could identify more than 120 new lineages within all major groups of the Phytomyxea which allows us to estimate that there are in the region of 100-200 species within the group. So far it was estimated, that there are 30-40 species of phytomyxids with DNA-data available for 10 species only. We could identify 3 new species and re-discover another 4 species which had last been seen in the mid twentieth century. The majority of our newly discovered species is marine. We could find two new species which are parasites of brown algae. Algal aquaculture is growing exponentially worldwide with multiple applications in the food, chemical and pharmaceutical industries which is adding economic importance to our findings. Microbial parasites are not well studied in aquaculture, hence phytomyxids will be a prime example to do this, as a considerable body of research on plant pathogenic species is already available which will be a very strong foundation for future research into these species. We could also find one new species which is parasitic to seagrasses and seegrass meadows, which are important ecological habitats, are under threat globally. Because the reasons for this seagrass dieback remain partly elusive more research into our newly discovered seagrass pathogenic species along with the high number of yet uncharacterised species will help to better understand the reasons for this dieback. Our research also showed, that phytomyxids did not co-evolve alongside their hosts, but that some species were formed after sudden changes of taxonomically unrelated hosts (e.g. from brown algae to plants). We could also identify a phytomyxid group which is the evolutionary transition between the free living vampire amoeba and the parasitic phytomyxids. These results will form the basis for future research into shared and monopolised processes between selected species to ultimately improve our understanding of the evolution of parasitism.