Project:New studies to add

Publications that describe symbiotic interactions that are not yet in the database.

Guidelines:

• Please list the DOI, or link to the publication full-text if a DOI is not available. A full citation is not necessary as the publication metadata can be retrieved from CrossRef with the DOI.
• If necessary, comment briefly on what information in the publication should be added to the database.
• Preprints can be listed here, but should only be added as database entries when a peer-reviewed version is published
• Remove entries from the list when the database has been updated.

Ciliates

• link flagellated endosymbionts in a Frontonia sp.
• https://www.nature.com/articles/s41467-024-54047-x Relatives of Ca. Azoamicus detected in groundwater metagenomes, assembled as circular-contig MAGs (cMAGs).
• https://doi.org/10.1093/ismejo/wraf203 Green alga Micractinium tetrahymenae in Tetrahymena utriculariae
• https://doi.org/10.1007/s00709-025-02097-3 Experimentally introduced Chlorella from original host Paramecium bursaria to P. multimicronucleatum

Insufficient information to relate host to symbiont species

• https://doi.org/10.1186/s40168-024-01809-w large scale study of ciliate associated bacteria, from single-ciliate-cell amplification libraries, but doesn't appear to have a table of which bacteria is associated with which ciliate?
• https://doi.org/10.1007/s42995-025-00295-9 methanogenic endosymbionts
• https://agro.icm.edu.pl/agro/element/bwmeta1.element.agro-443d0e0e-63a9-4de1-8030-60c431e77f83 Endosymbionts in Blepharisma japonicum (full text not yet found)
• https://academic.oup.com/mbe/article/17/2/251/1001839 Figure in online version too small to view but key to understanding

Reviews

• https://doi.org/10.1007/978-3-540-92677-1 Endosymbionts in Paramecium book
• https://doi.org/10.1007/978-3-540-92677-1_6 Diversity of Endosymbiotic Bacteria in Paramecium - in progress, stopped before section 5
• https://doi.org/10.1016/S0932-4739(11)80401-3 Endosymbionts in Paramecium calkinsi
• https://doi.org/10.1093/ismejo/wrae117 general review on ciliate symbioses

Preprints:

• https://doi.org/10.1101/2025.07.29.667580 (preprint) proposed "Candidatus Cillophilus ruminis", CAMVUJ01 (Amoebophilaceae) within rumen ciliate cytoplasm, but host only identified by morphology
• https://doi.org/10.1101/2025.07.24.665138 (preprint) Plagiopylean ciliate hosting Ca. Azoamicus mariagerensis symbiont in wastewater; other Azoamicus found in this study but their hosts unclear
• https://doi.org/10.1101/2025.07.30.667679 (preprint) Mixed symbiont transmission modes in Metopus ciliates and Methanocorpusculum symbionts

Trichomonas

• https://doi.org/10.3389/fmicb.2017.01188 Mycoplasma and Ureaplasma spp associated with Trichomonas vaginalis, detected by PCR from T. vaginalis cultures

Amoebae

• Item:Q1742 (no DOI, original URL defunct, archived at Internet Archive) - morphological description of Pelomyxa spp. symbionts
• https://doi.org/10.1186/s12866-016-0906-1 Acanthamoeba isolates containing chlamydia
• https://phaidra.univie.ac.at/detail/o:1356651.pdf Unpublished Masters thesis on chlamydial intranuclear symbiont of Naegleria clarki ("Pn")
• https://doi.org/10.1101/2024.11.01.621453 (preprint) Chlamydia in wild Dictyostelium isolates
• https://doi.org/10.1111/jeu.70008 Mayorella photosymbionts
• https://doi.org/10.3389/fmicb.2025.1634806 Review of Legionella pneumophila and Acanthamoeba spp.
• https://doi.org/10.1186/s12915-025-02280-1 Integration of giant viral genomes in Acanthamoebae genomes
• https://doi.org/10.1111/jeu.70011 Paramoeba with eukaryotic Perkinsela-like organism (PLO) endosymbiont
• https://doi.org/10.1155/japr/6626888 Acanthamoeba with Campylobacter jejuni endosymbionts
• https://doi.org/10.1038/s41467-024-52906-1 Acanthamoeba castellanii with three viral elements
• https://doi.org/10.3389/fmicb.2025.1537073 Bacteriophages of Paraburkholderia symbionts of Dictyostelium

Forams

• https://doi.org/10.1038/s41598-019-48166-5 bacteria related to sulfur cycling enriched in forams
• https://doi.org/10.1016/j.marmicro.2017.09.001 Review of prokaryotes associated with benthic forams, see their table 1
• https://doi.org/10.4319/lo.2014.59.6.1879 intracellular bacteria in Ammonia beccarrii under anoxic conditions

Termite gut flagellates

• https://doi.org/10.1083/jcb.94.3.697 Motility symbiont(s) of a devescovinid flagellate
• https://doi.org/10.1371/journal.pone.0233065 ASV study of gut protist associated microbes in Reticulitermes flavipes
• https://doi.org/10.1111/j.1550-7408.2011.00564.x EM study of symbionts from Barbulanympha and Urinympha from Cryptocercus punctulatus; intracellular localization observed
• https://doi.org/10.1128/mbio.00826-24 Endomicrobia comparative genomics, but no information on protist hosts; their table S3 lists bacterial MAGs, but termite host names are in separate Table S1, and no systematic information is provided on the protist hosts
• https://doi.org/10.1111/brv.13038 Review of protist symbionts of termites
• https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&doi=18ac2be7fd364d7871888f06b24b0d15223c7b9f#page=40 TEM study of symbionts in Joenia annectens; the intranuclear symbiont appears not to have been reported elsewhere
• https://doi.org/10.1007/s13199-025-01073-y Localization of spirotrichs to protists vs. free-swimming in gut

• https://doi.org/10.1099/mic.0.2007/009217-0 Endomicrobia in termite gut flagellates; unfortunately it is not clearly reported which symbiont phylotype comes from which flagellate

Other

• https://www.jstor.org/stable/43336527 https://doi.org/10.1111/j.1438-8677.1982.tb01611.x https://doi.org/10.1111/j.1438-8677.1983.tb01673.x Apparent "symbionts" of Chrysostephanosphaera and Lepochromulina in extracellular matrix, described as "refractive bodies" elsewhere (https://doi.org/10.1111/j.1756-1051.1998.tb01545.x), probably not bacteria
• Item:Q1104 - Check that examples listed in their table are included in DB
• https://www.nature.com/articles/s41598-021-82369-z presence of intracellular bacteria briefly mentioned
• https://doi.org/10.1038/ncomms11071 Lineage specificity of UCYN-A to related host species
• https://doi.org/10.1126/science.adk1075 argues that UCYN-A should be considered an organelle, rather than an endosymbiont
• https://doi.org/10.1371/journal.pone.0301343 Potential bacterial symbionts of Alexandrium catenella
• https://doi.org/10.3354/ame01440 Heterotrophic ?diazotrophs associated with dinoflagellate-cyanobacteria consortia
• https://doi.org/10.1128/microbiolspec.funk-0056-2016 Endohyphal symbionts of fungi
• https://doi.org/10.1016/j.cub.2024.09.009 "Non-photosynthetic lineages sibling to Cyanobacteria associate with eukaryotes in the open ocean"
• https://doi.org/10.1093/ismejo/wraf171 Potential new breviate-bacteria symbioses enriched in microcosms
• https://doi.org/10.1128/msystems.00261-25 Ca. Babelota associated with protists, but specific associations not named in main text
• https://doi.org/10.1002/mbo3.70018 Developing genetic tools for Bodo symbiosis
• https://doi.org/10.1007/s00436-025-08505-0 Intracellular bacteria in Balamuthia spp
• https://doi.org/10.1038/s41598-021-89072-z host specificity in cyanobionts of Ornithocercus (dinoflagellates)
• https://link.springer.com/article/10.1186/s12864-026-12517-0 N2-fixing symbionts of diatoms
• https://doi.org/10.1099/mgen.0.001642 Novel Holosporales endosymbionts of Bodo spp.
• https://doi.org/10.1111/jeu.70056 Review of microbiota within Blastocystis spp.
• https://doi.org/10.1111/jpy.70131 Rickettsial symbionts in Pleodorina green algae

Preprints

• https://doi.org/10.1101/2024.12.29.630703 (preprint) Screening of >100 protist metagenomes for potential symbionts

Viruses

• https://doi.org/10.1111/1462-2920.70155 Cyanophages in cyanobacterial endosymbiont of sponge
• https://doi.org/10.1128/jvi.00713-25 Giant Endogenous Viral Elements (GEVEs) in Euglena gracilis genome
• https://doi.org/10.1038/s41579-022-00754-5 Add giant viruses?
• https://doi.org/10.1016/j.cub.2024.04.085 large scale survey of published eukaryotic genome data for mirusviruses, using major capsid protein sequence as marker; three assemblies found with circular viral genomes

Relevant projects of similar scope to PPSDB

• https://doi.org/10.12688/wellcomeopenres.17222.2 Aquatic Symbiosis Genomics project - collab?
• https://doi.org/10.1093/nar/gkae1084 http://www.phi-base.org/ PHI-Base, gene-centric pathogen-host interaction database

Reviews:

• https://doi.org/10.1007/s00248-025-02509-0 Taxonomic revision of the Holosporales order
• https://doi.org/10.1146/annurev-micro-090817-062650 review of cyanobacterial symbionts of microalgae -- the reference numbering in the supplementary table appears to be incorrect, I cannot trace the cited studies