Figure 4: Diagram of the novel Glaucocystis taxonomic system based on the present study.

Six Glaucocystis (G.) species were classified based on morphological characteristics and molecular phylogeny of cultured material. Colony surface (blue) exhibit two cellulose fibril types under FE-SEM (Fig. 2): gauze fabric-like fibrils (left) and tightly arranged fibrils (right), indicated by two background designs. Periphery types A–C are distinguishable under UHVEM and TEM (Supplementary Fig. 4)13,14, indicated by enlarged diagram of flattened vesicles (yellow) in each species. Four types of cell wall shape at the cell poles are recognised under LM (Supplementary Fig. 1). Phylogeny is based on phylogenetic tree of the concatenated gene sequences (Supplementary Fig. 5); each species exhibits sufficient genetic distances from other species (Supplementary Figs 6–8).