Ramirez-Sanchez, O. | Search bioRxiv

bioRxiv2026

Strain-specific higher-order interactions break phylogenetic conservatism in microbial communities

Whether strains of the same species sharing the same ecological role are truly interchangeable has not been directly tested experimentally in communities, where higher-order interactions govern outcomes. Using 79 co-occurring Bacillaceae isolates from the Cuatrocienegas Basin, we combined whole-genome analyses with systematic strain substitutions in BARS, a three-species community in which a resistant strain protects a sensitive strain from an antagonist. Trait conservatism strongly predicted pairwise antagonistic outcomes. Yet across 34 assembled triads, 13 showed rescue beyond pairwise expectations and five showed suppression; single-strain substitutions rarely restored protection, although protection was recovered in one fully reconfigured triad. These outcomes could not be inferred from taxonomic relatedness, pangenomic content or pairwise assays; phylogenetic conservatism thus reaches its limit at the transition from pairwise to higher-order interactions. To explain this limit, we propose that strains behave as non-equivalent biological tiles whose interaction edges must align, a dynamic biological tessellation.

evolutionary biology↗

bioRxiv2019

Disentangling sRNA-Seq data to study RNA communication between species

Many organisms exchange small RNAs during their interactions, and these RNAs can target or bolster defense strategies in host-pathogen systems. Current sRNA-Seq technology can determine the small RNAs present in any symbiotic system, but there are very few bioinformatic tools available to interpret the results. We show that one of the biggest challenges comes from sequences that map equally well to the genomes of both interacting organisms. This arises due to the small size of the sRNA compared to large genomes, and because many of the produced sRNAs come from genomic regions that encode highly conserved miRNAs, rRNAs or tRNAs. Here we present strategies to disentangle sRNA-Seq data from samples of communicating organisms, developed using diverse plant and animal species that are known to exchange RNA with their parasites. We show that sequence assembly, both de novo and genome-guided, can be used for sRNA-Seq data, greatly reducing the ambiguity of mapping reads. Even confidently mapped sequences can be misleading, so we further demonstrate the use of differential expression strategies to determine the true parasitic sRNAs within host cells. Finally, we validate our methods on new experiments designed to probe the nature of the extracellular vesicle sRNAs from the parasitic nematode H. bakeri that get into mouse epithelial cells.

bioinformatics↗