Sofia Medvedeva

Widespread and intron-rich mirusviruses are predicted to reproduce in nuclei of unicellular eukaryotes - Nature Microbiology Environmental metagenomic explorations show that Mirusviricota lineages lack essential replication and transcription genes and contain spliceosomal introns, suggesting nuclear reproduction.

www.nature.com/articles/s41...

Thrilled to share our new study! We show that mirusviruses include lineages packed with spliceosomal introns and likely replicating in the nucleus of unicellular eukaryotes—a sharp contrast to most large and giant eukaryotic viruses that replicate in the cytoplasm.

Transcriptional landscape of the archaeal cell cycle is broadly conserved in eukaryotes The cell cycle is a series of events that occur from the moment of cell birth to cell division. In eukaryotes, cell growth, genome replication, genome segregation, and cytokinesis are strictly coordin...

Very happy to share the first publication from my PhD as a preprint!!
Are you an archaea enthusiast? A network afficionado? Do you love the cell cycle?
If you answered yes to any of those questions this preprint is for you! Little 🧵 (1/11)

www.biorxiv.org/content/10.1...

10/ We hope that our results will encourage to further characterize sheath in diverse archaeal lineages, understand its role in shaping microbial communities, and explore the ingenious ways viruses adapted to exploit these structures.

9/ We propose a novel model of viral egress in sheathed archaea. We hypothesize that secreted viral SH-like proteins may decrease the stability of the host sheath. Alternatively, they may disrupt sheath assembly, competing with the host SH monomers.

8/ Interestingly, we found SH-like proteins in viruses infecting sheathed archaea and we use them as markers to assign 580 new viral OTUs to sheathed hosts! What is the function of these viral SH-proteins? Using AlphaFold, we infer that they can form dimers with the host SH-proteins!

7/ Viruses employ sophisticated mechanisms to breach the cell walls of their hosts. However, it is unknown how they can break through the robust amyloid structure of the sheath. We searched for potential lysis-related genes in viruses infecting sheathed archaea.

6/ Phylogenetic analysis reveals that the current distribution of the sheath was shaped by a complex pattern of transfers and lineage-specific losses. These events indicate an active dynamic of the sheath in archaeal communities, which may have accompanied environmental adaptations.

5/ We find that sheaths are widespread across ANME-1 archaea. Sequence similarity suggests multiple acquisitions via recent horizontal gene transfers from Methanothrix and Methanospirillum.

4/ We reveal a large diversity of cap domains, which might adapt the sheath structure to specific environmental or physiological needs. For example, SH proteins with a long chain of Ig-like domains could form sheaths with adhesion properties.

3/ Using Foldseek we searched for structural homologues of SH proteins in archaeal genomes. We found them in four lineages, and for the first time in the ecologically important ANME-1 (methane oxidizers). SH proteins are present in multiple copies per genome (up to 40) and are highly expressed.

2/ Sheaths are made of SH proteins, organized into rings. SH protein consists of an amyloid domain (facing the interior of the sheath tube) and a “cap” domain. SH proteins of Methanospirillum and Methanothrix have no sequence similarity, so how can we identify sheath in other archaea?

1/ Sheaths were first discovered in two archaeal methanogens: Methanospirillum and Methanothrix. They are tube-like surface structures, shared by multiple cells within a filament, which remain largely understudied.

Sheaths are diverse and abundant cell surface layers in archaea Abstract. Prokaryotic cells employ multiple protective layers crucial for defense, structural integrity, and cellular interactions in the environment. Arch

Have you ever heard about sheaths? Happy to share our last paper with @sgribaldo.bsky.social and Guillaume Borrel @pasteur.fr where we investigated their distribution and evolution!
doi.org/10.1093/isme...
Below a thread of our major findings:

4/ We reveal a large diversity of cap domains, which might adapt the sheath structure to specific environmental or physiological needs. For example, SH proteins with a long chain of Ig-like domains could form sheaths with adhesion properties.

3/ Using Foldseek we searched for structural homologues of SH proteins in archaeal genomes. We found them in four lineages, and for the first time in the ecologically important ANME-1 (methane oxidizers). SH proteins are present in multiple copies per genome (up to 40) and are highly expressed.

2/Sheaths are made of SH proteins, organized into rings. SH protein consists of an amyloid domain (facing the interior of the sheath tube) and a “cap” domain. SH proteins of Methanospirillum and Methanothrix have no sequence similarity, so how can we identify sheath in other archaea?

1/ Sheaths were first discovered in two archaeal methanogens: Methanospirillum and Methanothrix. They are tube-like surface structures, shared by multiple cells within a filament, which remain largely understudied.