Biology subjects

Schön, M. E.

Publications and source records attributed to Schön, M. E..

3 recordsLinked to original sources

bioRxiv2025

Strain-level diversity of giant viruses infecting chlorarachniophyte algae in the subtropical North Pacific

Giant DNA viruses are ubiquitous among unicellular eukaryotes and occur in marine, freshwater, and terrestrial environments. Despite intense metagenomic data mining, their strain-level diversity remains largely unexplored. Here we introduce a model system comprising four isolates of a giant virus called ChlorV, which infects marine microalgae of the class Chlorarachniophyceae (Rhizaria) from station ALOHA, Hawaii. The ChlorV genomes are 469 kbp to 493 kbp long and encode approximately 400 proteins, at least 106 of which are present n purified virions. Although the four viral genomes are highly syntenic, they differ by several insertions and deletions that often encode methyltransferases. Interestingly, we found that some of these methyltransferase genes correlated with specific DNA methylation patterns in the ChlorV strain Our study describes the first giant viruses infecting the eukaryotic supergroup Rhizaria and demonstrates how viral strain-level variation in gene content and epigenetic features may affect eco-evolutionary processes in marine microalgae.

microbiology↗

bioRxiv2023

Phylogenomics and ancestral reconstruction of Korarchaeota reveals genomic adaptation to habitat switching

Our knowledge of archaeal diversity and evolution has expanded rapidly in the past decade. However, hardly any genomes of the phylum Korarchaeota have been obtained due to the difficulty in accessing their natural habitats and - possibly - their limited abundance. As a result, many aspects of Korarchaeota biology, physiology and evolution remain enigmatic. Here, we expand this phylum with five high-quality metagenome-assembled genomes. This improved taxon sampling combined with sophisticated phylogenomic analyses robustly places Korarchaeota at the base of TACK and Asgard clades, revisiting the phylums long-assumed position. Furthermore, we observe a clear split between terrestrial and marine thermal clades. Gene tree-aware ancestral reconstructions suggest that the last Korarchaeota common ancestor was a thermophilic autotroph. In contrast, Korarchaeaceae, the lineage where environmental transitions occurred, shifted towards a heterotrophic lifestyle. Terrestrial Korarchaeota gained many cas and CARF genes indicating they may need to manage viral infections. Together, our study provides new insights into these early diverging Archaea and suggests that gradual gene gain and loss shaped their adaptation to different thermal environments. ImportanceKorarchaeota are an ancient group of archaea, but their biology, physiology and evolution have remained obscure. Analysis of five novel Korarchaeota MAGs, and publicly available reference data provides robust phylogenomic evidence that Korarchaeota are placed at the base of Asgard archaea and TACK, revisiting the phylums long-assumed position. Gene content reconstruction suggests a versatile thermophilic and autotrophic last Korarchaeota common ancestor. Environmental distribution surveying of public databases places all Korarchaeota in thermophilic environments and indicates that their habitat is limited to hydrothermal vents and hot springs. Our modeling indicates at least two transitions linked to habitat switching between these environments in the evolutionary history of Korarchaeota. Both are linked to a significant alteration of the inferred ancestral gene content, including a shift towards a heterotrophic and potential scavenging lifestyle. Furthermore, hot spring Korarchaeota acquired various genes participating in resistance to viruses, suggesting they may need to manage frequent viral threats.

microbiology↗

bioRxiv2021

Picozoa are archaeplastids without plastid

The endosymbiotic origin of plastids from cyanobacteria gave eukaryotes photosynthetic capabilities and launched the diversification of countless forms of algae. These primary plastids are found in members of the eukaryotic supergroup Archaeplastida. All known archaeplastids still retain some form of primary plastids, which are widely assumed to have a single origin. Here, we used single-cell genomics from natural samples combined with phylogenomics to infer the evolutionary origin of the phylum Picozoa, a globally distributed but seemingly rare group of marine microbial heterotrophic eukaryotes. Strikingly, the analysis of 43 single-cell genomes shows that Picozoa belong to Archaeplastida, specifically related to red algae and the phagotrophic rhodelphids. These picozoan genomes support the hypothesis that Picozoa lack a plastid, and further reveal no evidence of an early cryptic endosymbiosis with cyanobacteria. These findings change our understanding of plastid evolution as they either represent the first complete plastid loss in a free-living taxon, or indicate that red algae and rhodelphids obtained their plastids independently of other archaeplastids.

evolutionary biology↗