Cellular & Molecular Imaging

Bacterial endosymbionts inhabit diverse niches within eukaryotic cells, yet their direct associations with mitochondria have remained enigmatic. Here we introduce mitobiosis, the phenomenon of bacterial residency inside mitochondria or tight association with them. Using a multimodal volumetric electron microscopy (vEM) framework spanning whole-cell reconstructions to subnanometer-scale electron tomography, we investigated two ecologically important eukaryotes: the tick Ixodes ricinus and the marine protist Diplonema japonicum. We show that Midichloria mitochondrii, the maternally transmitted symbiont of I. ricinus, penetrates into the intracristal space of host mitochondria, inducing ≥60-fold cristal expansion exceeding 1 μm in width. In diplonemids, we observed staged endosymbiotic interaction with host mitochondrion, including cases of complete engulfment by both mitochondrial membranes. These findings establish mitochondria as dynamic symbiotic niches and highlight vEM as a powerful tool for uncovering hidden organelle-microbe interactions. Mitobiosis extends the spectrum of organelle-associated symbioses and represents a conceptual advance in cell biology.

This dataset contains over 20000 images of Dipteran wings collected, mostly of mosquitos. Each image is accompanied by extensive metadata, accessible in the 00_metadata.* files. The dataset aims to facilitate research in wing geometric morphometry and support the development of machine learning models for advancing vector surveillance and research. It is a retrospective collection, harmonizing contributions from research projects conducted between 2008 and 2026. The detailed metadata on each sample and image is available in the 00_metadata.*. This table below will provide an overview of the scope and range of the collected metadata. Due to the retrospective nature of the dataset, images may vary significantly in aspects such as lighting, background, and capture conditions across different projects. Although extensive efforts were made to ensure comprehensive metadata, some entries remain incomplete. Missing metadata entries are marked as MISSING VALUE," while fields intentionally left blank are indicated with "-". For the full description of the dataset we refer to the associated publication: https://www.nature.com/articles/s41597-025-05043-3#Sec5

Light microscopy and scanning electron microscopy images of snow algae field samples containing Rosetta gen. nov., including type material.

The Darwin Tree of Life project has the goal to sequence the genomes of 70,000 species of eukaryotic organisms in Britain and Ireland. This is a collection of photographs of the samples included in the study, provided by the National History Museum (NHM).

The European Reference Genome Atlas (ERGA) initiative is a pan-European scientific response to current threats to biodiversity. Reference genomes provide the most complete insight into the genetic basis that forms each species and represent a powerful resource in understanding how biodiversity functions. This is a collection of the samples included in the study, provided by COPO at Earlham Institute.

The Darwin Tree of Life project has the goal to sequence the genomes of 70,000 species of eukaryotic organisms in Britain and Ireland. This is a collection of photographs of the samples included in the study, provided by the National History Museum (NHM).

Bacteria occupy heterogeneous environments, attaching and growing within pores in materials, living hosts, and matrices like soil. Systems that permit high-resolution visualization of dynamic bacterial processes within the physical confines of a realistic and tractable porous media environment are rare. Here we use microfluidics to replicate the grain shape and packing density of natural sands in a 2D platform to study the flow-induced spatial evolution of bacterial biofilms underground. We introduce a wildtype strain (Pantoea sp. YR343, n=3) or an EPS-defective strain (Pantoea sp. YR343 ΔUDP, n=3) to the porous media platform and then simulate a rainfall event using gravity-driven flow of bacterial growth media.

The neglected tropical disease schistosomiasis impacts over 700 million people globally. Schistosoma mansoni, the trematode parasite that causes the most common type of schistosomiasis, requires planorbid pond snails of the genus Biomphalaria to support its larval development and transformation to the cercarial form that can infect humans. A greater understanding of neural signaling systems that are specific to the Biomphalaria intermediate host could lead to novel strategies for parasite or snail control. This study examined a Biomphalaria glabrata neural channel that is gated by the neuropeptide FMRF-NH2. The Biomphalaria glabrata FMRF-NH2 gated sodium channel (Bgl-FaNaC) amino acid sequence was highly conserved with FaNaCs found in related gastropods, especially the planorbid Planorbella trivolvis (91% sequence identity). In common with the P. trivolvis FaNaC, the B. glabrata channel exhibited a low affinity (EC50: 3 x 10-4 M) and high specificity for the FMRF-NH2 agonist. Its expression in the central nervous system, detected with immunohistochemistry and in situ hybridization, was widespread, with the protein localized mainly to neuronal fibers and the mRNA confined to cell bodies. Colocalization of the Bgl-FaNaC message with its FMRF-NH2 agonist precursor occurred in some neurons associated with male mating behavior. At the mRNA level, Bgl-FaNaC expression was decreased at 20 and 35 days post infection (dpi) by S. mansoni. Increased expression of the transcript encoding the FMRF-NH2 agonist at 35 dpi was proposed to reflect a compensatory response to decreased receptor levels. Altered FMRF-NH2 signaling could be vital for parasite proliferation in its intermediate host and may therefore present innovative opportunities for snail control.

Many proteins of the Repeats in Toxins (RTX) protein family are toxins of Gram-negative pathogens including hemolysin A (HlyA) of uropathogenic E. coli. RTX proteins are secreted via Type I secretion systems (T1SS) and adopt their native conformation in the Ca2+-rich extracellular environment. Here we employed the E. coli HlyA T1SS as a heterologous system for the RTX toxin MbxA from the bovine pathogen Moraxella bovis. In E. coli the HlyA system successfully activates the heterologous MbxA substrate by acylation and secretes the precursor proMbxA and active MbxA allowing purification of both species. The activating E. coli acyltransferase HlyC recognizes the acylation sites in MbxA, but unexpectedly in a different acylation pattern as for its endogenous substrate HlyA. HlyC-activated MbxA shows host species-independent activity including toxicity against human lymphocytes and epithelial cells. Using live-cell imaging we show an immediate MbxA-mediated permeabilization and a rapidly developing blebbing of the plasma membrane in epithelial cells.

The cyanoHAB forming cyanobacteria Microcystis and Planktothrix frequently produce high intracellular amounts of microcystins (MCs) or anabaenopeptins (APs). In this study, chemically modified MCs and APs have been localized on a subcellular level in Microcystis and Planktothrix applying copper-catalyzed alkyne-azide cycloaddition (CuACC). For this purpose, three different non-natural amino acids carrying alkyne or azide moieties were fed to individual P. agardhii strains No371/1 and CYA126/8 as well as to M. aeruginosa strain Hofbauer showing promiscuous incorporation of various amino acid substrates during non-ribosomal peptide synthesis (NRPS). Moreover, CYA126/8 peptide knock-out mutants and non-toxic strain Synechocystis PCC6803 were processed under identical conditions. Simultaneous labelling of modified peptides with ALEXA405 and ALEXA488 and lipid staining with BODIPY 505/515 were performed to investigate the intracellular location of the modified peptides. Pearson correlation coefficients (PCC) obtained from confocal images were calculated between the different fluorophores and the natural autofluorescence (AF), and between labelled modified peptides and dyed lipids to investigate the spatial overlap between peptides and the photosynthetic complex, and between peptides and lipids. Overall, labelling of modified MCs (M. aeruginosa) and APs (P. agardhii) using both fluorophores revealed in-creased intensity in MC/AP producing strains. For Synechocystis lacking NRPS, no labelling using either ALEXA405 or ALEXA488 was observed. Lipid staining in M. aeruginosa and Synechocystis was intense while in Planktothrix it was more variable. When compared with AF, both modified peptides and lipids showed a heterologous distribution. In comparison, the correlation between stained lipids and labelled peptides was not increased suggesting a reduced spatial overlap.