Biology subjects

Rotterova, J.

Publications and source records attributed to Rotterova, J..

3 recordsLinked to original sources

bioRxiv2026

Distinct genomic adaptations of the methanogenic archaeal genus Methanocorpusculum to symbiosis with animals and protists

Most of our understanding of endosymbiosis originates from the bacterial endosymbionts of multicellular, terrestrial hosts, which represent habitats with dramatically different selective pressures than inside a protist cell. Methanogenic archaea from the genus Methanocorpusculum are among the few known intracellular archaea and form unique symbioses with both animal and protist hosts, providing a unique opportunity to contrast symbiont evolution and function in very distinct host types. Here, we conducted phylo- and pangenomic analyses on 106 Methanocorpusculum strains originating from animal and ciliate hosts as well as environmental habitats. We recovered two divergent clades corresponding to animal gut-associated and intracellular ciliate-associated/environmental lineages and found that ciliate-associated and environmental Methanocorpusculum are virtually indistinguishable functionally and phylogenetically. Ciliate-associated symbionts retained broad biosynthetic capacity and encoded functions related to osmotic stress tolerance and adhesion within the host cell, while animal gut-associated symbionts exhibited patterns of genome streamlining and nutrient scavenging consistent with host supply and immune adaptation. Our findings illuminate how the contrasting selective pressures of protists and animal hosts have driven divergent evolutionary and functional strategies in congeneric archaeal symbionts.

microbiology↗

bioRxiv2025

Population genomic insights into syntrophic symbioses between marine anaerobic ciliates and intracellular methanogens

Symbiotic interactions are an ecologically and evolutionary significant phenomenon pertaining to virtually every organism on Earth. For eukaryotes inhabiting extreme environments, syntrophic symbioses with microbes may be key to successfully colonizing new niches, such as globally expanding oxygen-depleted habitats. Multi-domain symbioses between microbial eukaryotes and intracellular methanogenic archaea are crucial to understanding the origins and mechanisms of eukaryotic anaerobiosis. Nearly all anaerobic ciliates, ecologically important protists found in diverse oxygen-depleted environments, host methanogenic endosymbionts, sometimes alongside bacterial partners, that facilitate their anaerobic metabolism. Although vertical symbiont transmission necessarily occurs during ciliate cell division, symbionts might occasionally be acquired horizontally. However, patterns of host-symbiont specificity and intraspecific variability remain poorly understood. Here, we present the first intra-specific genomic analysis of both host and symbionts in such partnerships, providing key insights into the fidelity of eukaryotic-prokaryotic liaisons in anoxia. We assessed the symbiont-host co-diversification and genetic variation across eleven populations of a single undescribed Metopus species hosting Methanocorpusculum cultured from intertidal sediment locations separated by meters to 1000s of kilometers. Our results show incongruency in host mitochondrial and symbiont phylogenies, indicating a mixed transmission mode. On a genomic level, both host and symbiont populations formed distinct location-specific clusters exhibiting no signs of isolation-by-distance. Instead, ecological factors appear to have driven population genomic divergence at least partly and likely led to differences in metabolic traits. Symbiont comparative and population genomics enable us to further comprehend the complex nature of these multi-partner syntrophic symbioses, crucial to interpreting cell-cell interactions across the domains of life.

microbiology↗

bioRxiv2024

Divergent marine anaerobic ciliates harbor closely related Methanocorpusculum endosymbionts

Ciliates are a diverse group of protists known for their ability to establish various partnerships and thrive in a wide variety of oxygen-depleted environments. Most anaerobic ciliates harbor methanogens, one of the few known archaea living intracellularly. These methanogens increase the metabolic efficiency of host fermentation via syntrophic use of host end-product in methanogenesis. Despite the ubiquity of these symbioses in anoxic habitats, patterns of symbiont specificity and fidelity are not well known. We surveyed two unrelated, commonly found groups of anaerobic ciliates, the Plagiopylea and Metopida, isolated from anoxic marine sediments. We sequenced host 18S rRNA and symbiont 16S rRNA marker genes as well as the symbiont ITS region from our cultured ciliates to identify hosts and their associated methanogenic symbionts. We found that marine ciliates from both of these co-occurring, divergent groups harbor closely related yet distinct intracellular archaea within the Methanocorpusculum genus. The symbionts appear to be stable at the host species level, but at higher taxonomic levels, there is evidence that symbiont replacements have occurred. Gaining insight into this unique association will deepen our understanding of the complex transmission modes of marine microbial symbionts, and the mutualistic microbial interactions occurring across domains of life.

microbiology↗