Biology subjects

Salas-Leiva, D.

Publications and source records attributed to Salas-Leiva, D..

3 recordsLinked to original sources

bioRxiv2026

An anaerobic Legionellales symbiont in Anaeramoeba pumila

Anaeramoeba pumila is a free-living anaerobic amoeba and the smallest known member of the Anaeramoebae, a phylum characterized by elaborate membrane-bound symbiosomes housing sulfate-reducing bacterial symbionts. Here, we report a draft nuclear genome assembly of A. pumila LANTAAN and describe the discovery, genomic characterization, and metabolic reconstruction of Candidatus Centrionella anaeramoebae gen. nov., sp. nov., an obligate intracellular symbiont of A. pumila belonging to the order Legionellales. Ca. Centrionella is a rare anaerobic member of Legionellales, a lineage otherwise comprising aerobic intracellular pathogens. Its genome (1.52 Mbp, 1,249 genes) is highly reduced and encodes an entirely anaerobic metabolism centered on substrate-level phosphorylation, arginine fermentation, and hydrogen oxidation via a bidirectional [NiFe]-hydrogenase -- metabolic strategies that parallel those independently evolved in the distantly related Anoxychlamydiales. The complete Dot/Icm type IVB secretion system is retained and likely mediates ongoing host manipulation, including via a large repertoire of predicted effector proteins. Strikingly, Ca. Centrionella has acquired eukaryotic Rac1-like GTPase genes from its host through horizontal gene transfer, with subsequent domain shuffling and duplication, that it may use to manipulate the cytoskeleton of its host. Unlike other Anaeramoeba symbionts, Centrionella localizes to the host microtubule-organizing center rather than a symbiosome, a localization consistent with cytoskeletal anchoring strategies described in other endosymbionts. The symbiosome, present in other Anaeramoeba species, appears to have been secondarily lost in A. pumila. A co-occurring Desulfobacter sp. LANTAAN, related to symbionts of other Anaeramoebidae, likely forms a tripartite syntrophic consortium by consuming hydrogenosomal fermentation end-products and supplying vitamin B12. Together, these findings illuminate the evolutionary transition in Legionellales from aerobic pathogenesis to anaerobic mutualism, providing a new model for the origins of intracellular symbiosis.

evolutionary biology↗

bioRxiv2026

DIVERGENT TRAJECTORIES FOR ANAEROBIC MITOCHONDRIAL EVOLUTION IN BREVIATE PROTISTS

Mitochondrion-related organelles (MROs) have evolved as adaptations to low oxygen conditions multiple times in the eukaryote tree of life. However, the evolutionary steps by which aerobic mitochondrial functions were replaced by anaerobic pathways are still poorly understood. The breviate Pygsuia biforma is particularly interesting because it is the only protist known to have replaced the canonical mitochondrial iron-sulfur cluster (ISC) system with a horizontally acquired SUF-like minimal system (SMS) protein. This functions within an MRO possessing a uniquely configured electron transport chain (ETC). To investigate the evolutionary path by which the P. biforma MRO evolved these features, we conducted a comparative transcriptomic study of eight diverse marine breviate species and predicted their MRO proteomes. We found three distinct patterns of iron-sulfur cluster biosynthesis machinery across the breviates where organisms would encode: the canonical ISC system alone, the ISC system and cytoplasmic SMS system, and a cytoplasmic and MRO-localized SMS system. Phylogenetic analyses suggests that the SMS system was acquired via lateral gene transfer in an ancestor of all breviates and later duplicated, with one copy gaining mitochondrial targeting and replacing the ISC system in a subset of breviates. We observed similarly divergent evolutionary trajectories for quinone-utilizing proteins. Two species have completely lost the ETC while the remaining lineages retain a partial ETC and mitochondrial contact site and cristae organizing system (MICOS), previously thought to be absent in breviates. These patterns reflect divergent biochemical configurations of MROs shaped by gene transfer, loss, and duplication within a single eukaryotic lineage and underscores dynamic remodeling of organellar metabolism in response to marine hypoxic environments.

evolutionary biology↗

bioRxiv2021

Unexpected organellar locations of ESCRT machinery in Giardia intestinalis and complex evolutionary dynamics spanning the transition to parasitism in the lineage Fornicata

Comparing a parasitic lineage to its free-living relatives is a powerful way to understand how the evolutionary transition to parasitism occurred. Giardia intestinalis (Fornicata) is a leading cause of gastrointestinal disease world-wide and is famous for its unusual complement of cellular compartments, such as having peripheral vacuoles instead of typical endosomal compartments. Endocytosis plays an important role in Giardias pathogenesis. Endosomal sorting complexes required for transport (ESCRT) are membrane-deforming proteins associated with the late endosome/multivesicular body (MVB). MVBs are ill-defined in G. intestinalis and roles for identified ESCRT-related proteins are not fully understood in the context of its unique endocytic system. Furthermore, components thought to be required for full ESCRT functionality have not yet been documented in this species. We used genomic and transcriptomic data from several Fornicata species to clarify the evolutionary genome streamlining observed in Giardia, as well as to detect any divergent orthologs of the Fornicata ESCRT subunits. We observed differences in the ESCRT machinery complement between Giardia strains. Microscopy-based investigations of key components of ESCRT machinery such as GiVPS36and GiVPS25 link them to peripheral vacuoles, highlighting these organelles as simplified MVB equivalents. Unexpectedly, we show ESCRT components associated with the Endoplasmic Reticulum, and for the first time, mitosomes. Finally, we identified the rare ESCRT component CHMP7 in several fornicate representatives, including Giardia, and show that contrary to current understanding, CHMP7 evolved from a gene fusion of VPS25 and SNF7 domains, prior to the last eukaryotic common ancestor, over 1.5 billion years ago. Our findings show that ESCRT machinery in G. intestinalis is far more varied and complete than previously thought, and associating to multiple cellular locations and presenting changes in ESCRT complement which pre-date adoption of a parasitic lifestyle.

evolutionary biology↗