A novel jakobid genus from the soil of an indoor plant.

Jakobids are a group of free-living heterotrophic flagellates that hold a key phylogenetic position for understanding early eukaryote evolution and are particularly notable for their gene-rich, bacteria-like mitochondrial genomes. Although the number of formally described species is small, jakobids are frequently detected in anoxic marine habitats. However, their edaphic diversity remains unexplored, with the few documented isolations from soil over the past two decades, each yielding a new genus. Here, we describe a novel jakobid, Celatomonas quasimodo gen. et sp. nov., isolated from commercial potting soil used for cultivating indoor plants. The organism was characterised by light and scanning electron microscopy, and its phylogenetic position was inferred using 18S rRNA gene phylogenetic analysis. While exhibiting typical jakobid features, the cells adopt a highly unusual curved-triangular morphology during division, which has not been reported for any other jakobid. Phylogenetic analysis placed C. quasimodo as the firmly supported sister lineage of Moramonas marocensis within the family Moramonadidae (suborder Histionina). Despite this close affinity, the two taxa present a level of 18S rRNA gene divergence comparable to that between already recognised genera of Moramonadidae. Together, these data support the recognition of Celatomonas quasimodo as a new genus and species within Moramonadidae. Furthermore, screening of soil environmental DNA datasets revealed the presence of multiple novel jakobid lineages, alongside a novel jakobid clade (JENV-1) of uncertain phylogenetic position from equatorial environments. This newly described jakobid genus provides a valuable model for future comparative studies of cellular ultrastructure and the evolution of jakobid mitochondrial genomes. Combined with the environmental DNA screening results, our findings underscore the importance of soil habitats as reservoirs of unexplored eukaryotic diversity and provide new insights into jakobid systematics.