Backgrounds: Microbial eukaryotes are integral members of marine ecosystems in terms of cell abundance, biomass, activity, and diversity and they play crucial roles in food webs and biogeochemical cycles. They are difficult to grow in culture and often cannot be identified by regular microscopy, so a variety of molecular tools have been applied to study their diversity. Objectives: The objective is to identify the main microeukaryotic players in marine planktonic ecosystems and to determine the ecological performance of novel lineages. Methods: Microeukaryotic diversity is first described by sequencing a phylogenetic marker gene from mixed assemblages, and then supported by PCR-free metagenomes. Specific probes are designed to target novel lineages by FISH (Fluorescent In situ Hybridization). Single cell genomics is used to access the genomes of uncultured cells. Conclusions: Environmental molecular surveys have unveiled a large phylogenetic diversity and the presence of novel diversity. In this talk I will focus on a set of novel lineages within the stramenopiles that account for a significant fraction of the molecular signal, the MAST lineages. The abundance, distribution and genetic structure of the main MAST groups in the marine environment will be presented using specific probes for direct observation by FISH and parallel sequencing surveys using community DNA. MAST cells are also well represented in a collection of SAGs (Single Amplified Genomes) prepared from open sea surface samples, and preliminary genomic data for these uncultured cells will be presented. Certainly, the ecological and evolutionary significance of novel protist diversity is remarkable

7th Congress of European Microbiologists Federation of European Microbiological Societies (FEMS 2017), 9-13 July 2017, Valencia, Spain

Peer Reviewed