DOI: 10.6084/m9.figshare.30442973.v2
title: <i>Aerobic sister-lineage of Breviates has gene-rich mitochondrial genomes</i>

description: Breviates are anaerobic/micro-aerophilic flagellates that harbor hydrogen-producing MROs and lack a mitochondrial genome (mtDNA). Breviates alongside apusomonads and opisthokonts (the group that includes animals and fungi) form a lineage called Obazoa. To identify novel microaerophiles within Obazoa, we sampled an intertidal mudflat and used flow cytometry-based single-cell sorting to generate single-cell amplified genomes (SAGs). We found a new lineage closely related to known breviates based on phylogenomics. Surprisingly, we recovered several mtDNAs in the breviate-related (BR) SAGs, which encode most of the genes involved in electron transport chain complexes. These BR mtDNAs harbour rare mitochondrial genes such as <i>rpl21</i> and <i>rnpB</i> that are lost or usually encoded in nuclear genomes in most other eukaryotes. In some of the nuclear genomes of the corresponding BR SAGs, we detected genes encoding enzymes for anaerobic respiration and hydrogen production (e.g., [FeFe] hydrogenase and pyruvate:ferredoxin oxidoreductase) suggesting that these organisms could be facultative anaerobes. We additionally recovered mtDNAs from SAGs of apusomonads that are gene-rich compared to known mtDNAs from this group. The identification and initial characterization of a new clade within Obazoa provides avenues to better understand the process of mitochondrial reductive evolution in breviates and apusomonads, and highlights the important role of microscope-independent approaches, such as fluorescence-activated cell sorting and single cell genomics, in discovering new lineages.<b>Folder descriptions:</b><b>NOTE**: </b><i>red labels in the treefiles are dimmed paralogs, contaminants, or different proteins and were removed in the final analyses.</i><b>Figure1_FigureS1_PhyloFisher</b>Fig1_Pooled_SAGs: files used to produce Fig 1 tree.concat_matrix: matrix file and indicesgenes: gene files used to construct the matrixtreefiles: intermediate and final tree files under the model PMSF C60Fig1S_NotPooled_SAGs: files used to produce Fig 1S treeconcat_matrix: matrix file and indicesgenes: gene files used to construct the matrixtreefiles: intermediate and final tree files under the model PMSF C60<b>Figure2_18S_tree_and_algnments</b>18S rDNA sequences of newly identified BR and APU aligned with the 18S rRNA gene alignments obtained from Torruella et al. 2022 (https://doi.org/10.1111/jeu.12956). contains mafft aligned file, trimmed file, and all IQ-TREE outputs, including the treefile. <b>Figure3A_Williamson2025_dataset_sequences_trees</b>cleaned_alignments: confirmed genes from BR and APU SAGs used in the matrixconcatenated_matrix_iqtree: matrix and iqtree filesinitial_sgtree_preclean: initial single-gene trees to screen orthologs for the corresponding SAGsWilliamson2025_gene_name.txt: list of gene file and its corresponding gene names<b>Figure3B_ETC_sequences_and_trees</b>Concatenated_IQtrees: matrix and treefiles used for Fig 2BCore_ETC_24_genes: files used to generate single-gene treesAdditional files: also contain files for Fig S2 (used modelfinder to estimate the tree)<b>Figure4_Mitochondrial_genomes</b>14 Mitochondrial genomes from this study. Used to generate Fig 4.<b>Figure5_splitSDH2_alignments</b>Alignments of SDH2/SDHB from eukaryotes and split genes from euglenozoans and from this study<b>Figure6_mitochondria_proteins_MRO_MTS</b>single-gene trees used to find MRO and mitochondrial proteins in the BR SAGs from Improt_Chaperones, Iron_sulfur, and MRO_genes.also contain results for searching mitochondrial targeting sequence analyses, using MitoFates, MitoProt, targetP, and TPpred3.<br>