| 1. |
- Adl, Sina M., et al.
(författare)
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Revisions to the Classification, Nomenclature, and Diversity of Eukaryotes
- 2019
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Ingår i: Journal of Eukaryotic Microbiology. - : WILEY. - 1066-5234 .- 1550-7408. ; 66:1, s. 4-119
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Tidskriftsartikel (refereegranskat)abstract
- This revision of the classification of eukaryotes follows that of Adl et al., 2012 [J. Euk. Microbiol. 59(5)] and retains an emphasis on protists. Changes since have improved the resolution of many nodes in phylogenetic analyses. For some clades even families are being clearly resolved. As we had predicted, environmental sampling in the intervening years has massively increased the genetic information at hand. Consequently, we have discovered novel clades, exciting new genera and uncovered a massive species level diversity beyond the morphological species descriptions. Several clades known from environmental samples only have now found their home. Sampling soils, deeper marine waters and the deep sea will continue to fill us with surprises. The main changes in this revision are the confirmation that eukaryotes form at least two domains, the loss of monophyly in the Excavata, robust support for the Haptista and Cryptista. We provide suggested primer sets for DNA sequences from environmental samples that are effective for each clade. We have provided a guide to trophic functional guilds in an appendix, to facilitate the interpretation of environmental samples, and a standardized taxonomic guide for East Asian users.
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| 2. |
- Eglit, Yana, et al.
(författare)
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Meteora sporadica, a protist with incredible cell architecture, is related to Hemimastigophora
- 2024
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Ingår i: Current Biology. - : Elsevier. - 0960-9822 .- 1879-0445.
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Tidskriftsartikel (refereegranskat)abstract
- “Kingdom-level” branches are being added to the tree of eukaryotes at a rate approaching one per year, with no signs of slowing down.1,2,3,4 Some are completely new discoveries, whereas others are morphologically unusual protists that were previously described but lacked molecular data. For example, Hemimastigophora are predatory protists with two rows of flagella that were known since the 19th century but proved to represent a new deep-branching eukaryote lineage when phylogenomic analyses were conducted.2 Meteora sporadica5 is a protist with a unique morphology; cells glide over substrates along a long axis of anterior and posterior projections while a pair of lateral “arms” swing back and forth, a motility system without any obvious parallels. Originally, Meteora was described by light microscopy only, from a short-term enrichment of deep-sea sediment. A small subunit ribosomal RNA (SSU rRNA) sequence was reported recently, but the phylogenetic placement of Meteora remained unresolved.6 Here, we investigated two cultivated Meteora sporadica isolates in detail. Transmission electron microscopy showed that both the anterior-posterior projections and the arms are supported by microtubules originating from a cluster of subnuclear microtubule organizing centers (MTOCs). Neither have a flagellar axoneme-like structure. Sequencing the mitochondrial genome showed this to be among the most gene-rich known, outside jakobids. Remarkably, phylogenomic analyses of 254 nuclear protein-coding genes robustly support a close relationship with Hemimastigophora. Our study suggests that Meteora and Hemimastigophora together represent a morphologically diverse “supergroup” and thus are important for resolving the tree of eukaryote life and early eukaryote evolution.
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| 3. |
- Lax, Gordon, et al.
(författare)
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Hemimastigophora is a novel supra-kingdom-level lineage of eukaryotes
- 2018
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Ingår i: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 564:7736, s. 410-414
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Tidskriftsartikel (refereegranskat)abstract
- Almost all eukaryote life forms have now been placed within one of five to eight supra-kingdom-level groups using molecular phylogenetics(1-4). The 'phylum' Hemimastigophora is probably the most distinctive morphologically defined lineage that still awaits such a phylogenetic assignment. First observed in the nineteenth century, hemimastigotes are free-living predatory protists with two rows of flagella and a unique cell architecture(5-7); to our knowledge, no molecular sequence data or cultures are currently available for this group. Here we report phylogenomic analyses based on high-coverage, cultivation-independent transcriptomics that place Hemimastigophora outside of all established eukaryote supergroups. They instead comprise an independent supra-kingdom-level lineage that most likely forms a sister clade to the 'Diaphoretickes' half of eukaryote diversity (that is, the 'stramenopiles, alveolates and Rhizaria' supergroup (Sar), Archaeplastida and Cryptista, as well as other major groups). The previous ranking of Hemimastigophora as a phylum understates the evolutionary distinctiveness of this group, which has considerable importance for investigations into the deep-level evolutionary history of eukaryotic life-ranging from understanding the origins of fundamental cell systems to placing the root of the tree. We have also established the first culture of a hemimastigote (Hemimastix kukwesjijk sp. nov.), which will facilitate future genomic and cellbiological investigations into eukaryote evolution and the last eukaryotic common ancestor.
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| 4. |
- Williams, Shelby K., et al.
(författare)
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Extreme mitochondrial reduction in a novel group of free-living metamonads
- 2023
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- 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 relative to aerobic mitochondria, however the degree of reduction varies markedly over the metamonad tree. To further investigate metamonad MRO diversity, we generated high quality draft genomes, transcriptomes, and predicted proteomes for five recently discovered free-living metamonads. Phylogenomic analyses place these organisms in a clade sister to the Fornicata – a group of metamonads that includes parasitic and free-living diplomonads and Carpediemonas-like organisms. Extensive bioinformatic analyses of the manually curated gene models showed that these organisms have extremely reduced MROs in comparison to other free-living metamonads. Loss of the mitochondrial iron-sulfur cluster (ISC) 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 (SMS) Fe/S cluster pathway through lateral gene transfer (LGT). One of the isolates, named ‘RC’, appears to have undergone even more drastic mitochondrial reduction losing almost all other detectable MRO-related functions. The extreme mitochondrial reduction observed within this free-living anaerobic protistan clade is unprecedented and demonstrates that mitochondrial functions, under some conditions, can be almost completely lost even in free-living organisms.
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