Data from: Extreme mitochondrial reduction in a novel group of free-living metamonads

Metamonads are a diverse group of heterotrophic microbial eukaryotes
adapted to living in hypoxic environments. All metamonads but one harbour
metabolically altered ‘mitochondrion-related organelles’ (MROs) with
reduced functions, however the degree of reduction varies. Here, we
generate high-quality draft genomes, transcriptomes, and predicted
proteomes for five recently discovered free-living metamonads.
Phylogenomic analyses placed these organisms in a group we name the ‘BaSk’
(Barthelonids+Skoliomonads) clade, a deeply branching sister group to the
Fornicata, a phylum that includes parasitic and free-living flagellates.
Bioinformatic analyses of gene models shows that these organisms are
predicted to have extremely reduced MRO proteomes in comparison to other
free-living metamonads. Loss of the mitochondrial iron-sulfur cluster
assembly system in some organisms in this group appears to be linked to
the acquisition in their common ancestral lineage of a SUF-like minimal
system Fe/S cluster pathway through lateral gene transfer. One of the
isolates, Skoliomonas litria, appears to have lost all other known MRO
pathways. No proteins were confidently assigned to the predicted MRO
proteome of this organism suggesting that the organelle has been lost. The
extreme mitochondrial reduction observed within this free-living anaerobic
protistan clade demonstrates that mitochondrial functions may be
completely lost even in free-living organisms.