Burkart, F. | bioRxiv Science

bioRxiv2026

Interspecies transfer of giant virulence-factor-like proteins in a bacterial symbiosis

The transfer of virulence factors into eukaryotic cells is a hallmark of bacterial pathogenesis. We report the expression, interspecies transfer, subcellular localization, and potential functions of three unusually large virulence factor-like proteins that underlie a bipartite mutualistic bacterial symbiosis. These proteins are synthesized by green sulfur bacterial epibionts surrounding a central motile chemoheterotroph in the multicellular phototrophic consortium Chlorochromatium aggregatum. While symbiosis-proteins remain intracellular during axenic epibiont growth, they are transferred to the partner bacterium in the association. An RTX-like protein secreted towards the central bacterium is capable of degrading its alginate capsule, thereby promoting direct cell-to-cell contact. Two gigantic hemagglutinin-like proteins are predicted to fold when binding extracellular Ca2+ to form Type 6-like auto injection needles, explaining their observed transfer into the central bacterium. These functionalities extend far beyond the known pathogenic interactions of bacteria with eukaryotes and provide new perspectives on the evolution of bacterial virulence factors.

microbiology↗

bioRxiv2023

Touching the (almost) untouchable: a minimally-invasive workflow for microbiological and biomolecular analyses of cultural heritage objects

Microbiological and biomolecular approaches to cultural heritage research have expanded the established research horizon -from the prevalent focus on the cultural objects conservation and human health protection to the relatively recent applications to provenance inquiry and assessment of environmental impacts on heritage objects in a global context of a changing climate. Standard microbiology and molecular biology methods were developed for other materials, specimens, disciplines and contexts. Although they could in principle be applied to cultural heritage research, certain characteristics common to several heritage objects - such as uniqueness, fragility, high value and restricted access, demand tailored approaches. In addition, samples from heritage objects often yield low microbial biomass, rendering them highly susceptible to cross-contamination. Therefore, dedicated methodology that addresses these material limitations and operational hurdles along all procedural steps are needed. Here were propose a step-by-step standardized laboratory and bioinformatic workflow to analyse the microbiome of cultural heritage objects. The methodology was developed targeting the challenging side of the spectrum of cultural heritage objects, such as the delicate written record, while retaining modularity and flexibility to adapt and/or upscale the proposed workflow to heritage artefacts of a more robust nature or larger dimensions. We hope this review and workflow will facilitate the interdisciplinary inquiry and interactions among the cultural heritage research community.

microbiology↗