Morphology, Ultrastructure, and Mitochondrial Genome of the Marine Non-Photosynthetic Bicosoecid Gen. et sp. nov.

In this paper, we describe a novel bacteriophagous biflagellate, with two smooth flagellae, isolated from material collected from a rock surface in the Kvernesfjorden (Norway). This flagellate was characterized by scanning and transmission electron microscopy, fluorescence, and light microscopy. The sequence of the small subunit ribosomal RNA gene (18S) was used as a molecular marker for determining the phylogenetic position of this organism. Apart from the nuclear ribosomal gene, the whole mitochondrial genome was sequenced, assembled, and annotated. Morphological observations show that the newly described flagellate shares key ultrastructural characters with representatives of the family Bicosoecida (Heterokonta). Intriguingly, mitochondria of frequently associate with its nucleus through an electron-dense disc at the boundary of the two compartments. The function of this association remains unclear. Phylogenetic analyses corroborate the morphological data and place with other sequence data of representatives from the family Bicosoecida. We describe as a new species from a new genus in this family.