Session Soil Protists

Edward Mitchell (Chair)

Protists are a major component of soil biota both in terms of diversity and functional importance. Yet they remain less studied than other groups of soil organisms. The methodological limitations that explained this have now mostly been overcome and we see a clear increase in number of studies, especially those using high throughput sequencing (HTS) approaches to address biodiversity and function questions. This makes it all the more crucial to discuss, as a community, the current state of the art, knowledge gaps and ways to fill them. In this session I would like to invite colleagues to present talks aiming to cover the many topics directly related to soil protists including:

• Natural ecosystems and agro-ecosystems
• Biodiversity (direct observation and HTS)
• Taxonomy (morphology and molecular)
• Phylogeny and evolution
• Biogeography / Macroecology
• Functional ecology – links to ecosystem function
• Feeding habits, trophic roles

A mix of case studies and more general overviews/review would be welcome.

Session Anaerobic Protists

Ivan Cepicka (Chair)

Anoxic freshwater and marine sediments as well as the digestive tracts of animals are inhabited by diverse communities of protists, which are notable for having transformed mitochondria variously adapted to anaerobic metabolism. The final metabolic byproducts of these so-called mitochondrion-related organelles usually include molecular hydrogen, and, as means for its disposal, anaerobic protists have repeatedly entered into symbioses with bacteria or archaea that utilize hydrogen. These syntrophic symbioses have been recently attracting the attention of biologists because their intersection with aspects of climate science, including production of the greenhouse gas methane, poisonous hydrogen sulfide, and denitrification of the environment. Despite the obvious importance of anaerobic protists, their diversity is still only poorly documented. This symposium covers all aspects of the biology of anaerobic protists, both free-living and endobiotic, as well as their syntrophic symbioses with prokaryotes.

Session Ciliates as model organisms

Alexey Potekhin and Martin Simon (Chairs)

Ciliates serve as model organisms in different biological disciplines. Studies on ciliates have provided highly valuable insights into genetics and epigenetics, nucleus functions, non-coding RNA functions and chromatin structure, cell biology and physiology, cell signalling and cytoskeleton, structural heredity, evolution of eukaryotic cells, and much more. Molecular sequencing and especially genomics of ciliates continue to expand, now including more and more representatives of less known groups or from yet undersampled habitats, thus increasing the choice of the experimental models objects within the Ciliophora. The session will cover a broad spectrum of actual highlights in ciliate biology.

Session Algae and cyanobacteria as endosymbionts

Tatyana Darienko and Thomas Pröschold (Chairs)

Protists such as ciliates, amoebae and foraminifers often live in symbiosis with algae and cyanobacteria. The algal endosymbionts known as zoochlorellae and as zooxanthellae belong to different lineages of green and red algae and stramenopiles (dinoflagellates, and chrysophytes). Cyanobacteria occur as cyanelles in testate amoebae and marine diatoms. This session aims to demonstrate the current status of the biodiversity and evolution of these endosymbionts based on phylogeny and phylogenomics in comparison with their free-living relatives. Studies focusses on interactions between host/symbionts and their biogeographical pattern are also welcome. We especially encourage submissions about non-model organisms.

Session Terrestrial algae and the evolutionary origin of a multicellular land flora

Jan De Vries and Sebastian Hess (Chairs)

Algae from various lineages have successfully established a foothold on land. Their communities dwell in soil and surfaces such as rocks. Yet only once did terrestrial algae rise above their substrate and give rise to the dominant land flora: the streptophyte algae from which the embryophytes emerged. Irrespective of their evolutionary footprint, all terrestrial algae exhibit instructive traits, including tolerance to terrestrial stressors, specialized metabolism, and multicellular growth. In this session, we would like to capture the phylodiversity of terrestrial algae and their traits.

Session Protists associated with crops in land plants and aquaculture

Sigrid Neuhauser (Chair)

Protist parasites associated with land- and aquatic crops include organisms from diverse taxonomic groups such as Oomycetes, Rhizaria (e.g. Phytomyxea, Vampyrellida, Cercozoa) or Excavata (e.g. Phytomonas). Some of them are well known, however, knowledge about the impact and biology of most of these interactions remains scarce. Over the last years new tools allow us to detect, identify, and study those organisms in a more targeted way. This session aims to unite research on all groups of protists that is associated with plants or aquatic crops and aims to understand novel and established biodiversity, or which provide insights into their biology and ecology.

Session: Extreme environments and climate change 

Nicole Aberle-Malzahn and Stephen Wickham (Chairs)

Protists inhabit all types of terrestrial and aquatic environments and show high adaptation potential and trait flexibility in relation to environmental conditions. If Baas Beckling’s hypothesis that “everything is everywhere but the environment selects” is true, then extreme environment can be expected to show maximal selection. These environments are characterized by conditions beyond the optimal range, including extreme pH, temperature, salinity, radiation, and pressure conditions that are found i.e. in polar, desert, high altitude and deep sea habitats. However, despite such harsh conditions, extreme environments harbour a large variety of protists, thus contributing considerably to global biodiversity and ecosystem functions. Extreme environments harbour unique and complex protist communities with a high adaptative potential and flexibility to changes in environmental conditions. This session aims for contributions focussing on auto-, mixo- and heterotroph protist communities from extreme environments and their responses to changes in environmental conditions including climate change impacts. Studies from observational and experimental studies are welcome.

Session NGTax Symposium

Giulio Petroni and Valentina Serra (Chairs)

Next Generation Taxonomy (NGTax) is a multidisciplinary workflow recently proposed, which integrates the holobiont concept into traditional and integrative taxonomy, leveraging the power of high-throughput DNA sequencing. In detail, this approach combines traditional taxonomic techniques (living, observation, staining, morphometry), to ultrastructural (electron microscopy), molecular, phylogenetic, and genomics analyses of the ciliate host and its symbionts, if any. In particular, the ciliate mitogenome and obligate symbionts are proposed as additional taxonomic descriptors, in order to obtain the most comprehensive characterization of the organism(s). Whenever possible, also the complete genome of the symbiont is provided. In this section we present scientific contributions dealing with ciliate’s description and redescription, that move in the direction of NGTax approach, as well as works on host-symbionts interaction, and/or genomics/phylogenomic studies stemming from this research field.

Session Pathogenic protists

Vyacheslav Yurchenko (Chair)

At least 15% of known protists have symbiotic or parasitic life styles with considerably varying host-specificities. In principle, any other eukaryotic organism can function as host, including humans. Pathogenic protists do not only use other organisms as hosts, but also cause disease. Some of these microorganisms are of prime importance for human and animal health and many of the diseases caused by protists are neglected. Moreover, many pathogenic protists are opportunists and cause more severe disease in immunocompromised individuals.