Biology subjects

Geier, B.

Publications and source records attributed to Geier, B..

6 recordsLinked to original sources

bioRxiv2026

Spatial lipidomics suggests fatty acid scavenging by an intranuclear parasite

Bacteria of the family Endozoicomonadaceae are widely associated with marine animals, yet their in situ metabolism remains mostly unknown. Genomic studies suggest that members of this family engage in extensive metabolic exchange with their hosts, ranging from nutrient provision in mutualistic sponge and coral symbioses to strong dependence on host metabolites like lipids in parasitic associations. Here, we study the lipid phenotype of the parasitic bacterium Candidatus Endonucleibacter childressi in its native tissue environment. The bacterium infects epithelial cells in the gill of the deep-sea mussel Gigantidas childressi and co-occurs with the mussel chemosynthetic symbionts providing a system to compare lipid profiles of symbiotic and parasitic gammaproteobacteria. We linked bacterial identity to metabolic phenotypes by combining mass spectrometry imaging with 16S rRNA fluorescence in situ hybridization. We identified phospholipids characteristic of regions infected with Ca. Endonucleibacter childressi. A subset of these lipids was also detected in symbiont-colonized regions, revealing a partial overlap in the phospholipid profiles of the two gammaproteobacteria. Fatty acids from PEs assigned to Ca. Endonucleibacter childressi contained polyunsaturated fatty acids such as FA 16:3, FA 18:3 or FA 18:4 which have not been reported from cultured close relatives. We hypothesize that the observed fatty acid profile may reflect adaptations to a host-associated lifestyle which involves the acquisition and remodeling of host-derived fatty acids. Our findings demonstrate the value of characterizing bacterial metabolic phenotypes directly in their native tissue environment and highlight the potential of spatial lipidomics to reveal metabolic dependencies in host-microbe associations.

microbiology↗

bioRxiv2026

Basal gland localization and focal distribution of OLFM4-expressing cells in increasing severity of gastric intestinal metaplasia

Patients with gastric intestinal metaplasia (GIM), a precancerous lesion, are at high risk for progressing to gastric cancer. Identifying these patients is critical to enable gastric cancer interception. Current approaches rely primarily on histologic evaluation of GIM severity and extent, which may be improved by incorporating molecular features that distinguish high-risk lesions. Our prior single-cell and spatial transcriptomics study identified differentially expressed genes associated with the highest-risk category of GIM. They included ANPEP expressed in enterocytes and CPS1 and OLFM4 expressed in intestinal stem-like or progenitor cells. We evaluated the protein expression and localization of these three markers to understand the cellular features associated with GIM risk and their spatial distribution within metaplastic tissues. Using multiplex immunofluorescence, whole slide image analysis and confocal microscopy, we examined protein expression from 100 tissue biopsies annotated for metaplasia severity using the Operative Link on Gastric Intestinal Metaplasia Assessment (OLGIM) system. Tissue samples included control gastric tissue, GIM, dysplasia and adenocarcinoma. Quantitative whole slide image analysis demonstrated that CPS1 expression had a modest association with disease severity. Although ANPEP was strongly associated with GIM severity, it was also frequently expressed in stromal regions outside epithelial glands. In contrast, OLFM4 expression was largely restricted to epithelial glands and showed a strong association with increased OLGIM severity. These OLFM4-positive epithelial cells were present in discrete glandular foci that expanded with increasing severity of metaplasia. Within individual metaplastic glands, OLFM4 expression was highest at the gland base with decreased expression toward the gland surface. Overall, these findings identified OLFM4 as a protein marker associated with high-risk GIM. The spatial organization of OLFM4-expressing cells at the base of metaplastic glands and their focal expansion within tissues suggest the presence of a stem cell-like epithelial compartment that may contribute to the progression of GIM towards gastric cancer.

cancer biology↗

bioRxiv2020

Becoming symbiotic - the symbiont acquisition and the early development of bathymodiolin mussels

Symbiotic associations between animals and microorganisms are widespread and have a profound impact on the ecology, behaviour, physiology, and evolution of the host. Research on deep-sea mussels of the genus Bathymodiolus has revealed how chemosynthetic symbionts sustain their host with energy, allowing them to survive in the nutrient-poor environment of the deep ocean. However, to date, we know little about the initial symbiont colonization and how this is integrated into the early development of these mussels. Here we analysed the early developmental life stages of B. azoricus, "B". childressi and B. puteoserpentis and the changes that occur once the mussels are colonized by symbionts. We combined synchrotron-radiation based {micro}CT, correlative light and electron microscopy and fluorescence in situ hybridization to show that the symbiont colonization started when the animal settled on the sea floor and began its metamorphosis into an adult animal. Furthermore, we observed aposymbiotic life stages with a fully developed digestive system which was streamlined after symbiont acquisition. This suggests that bathymodiolin mussels change their nutritional strategy from initial filter-feeding to relying on the energy provided by their symbionts. After [~]35 years of research on bathymodiolin mussels, we are beginning to answer fundamental ecological questions concerning their life cycle and the establishment of symbiosis.

zoology↗

bioRxiv2020

CHEMHIST, connecting structure and function from organisms to molecules in small animal symbioses through chemo-histo-tomography

Our understanding of metabolic interactions between small symbiotic animals and bacteria or parasitic eukaryotes that reside within their body is extremely limited. This gap in knowledge originates from a methodological challenge, namely to connect histological changes in host tissues induced by beneficial and parasitic (micro)organisms to the underlying metabolites. To close this gap, we developed chemo-histo-tomography (CHEMHIST), a culture-independent approach to connect anatomic structure and metabolic function in millimeter-sized symbiotic animals. CHEMHIST combines spatial metabolomics based on mass spectrometry imaging (MSI) and microanatomy-based micro-computed X-ray tomography (microCT) on the same animal. Both high-resolution MSI and microCT allowed us to correlate the distribution of metabolites to the same animals three-dimensional (3D) histology down to sub-micrometer resolutions. Our protocol is compatible with tissue specific DNA sequencing and fluorescence in situ hybridization (FISH) for the taxonomic identification and localization of the associated micro(organisms). Building CHEMHIST upon in situ imaging, we sampled an earthworm from its natural habitat and created an interactive 3D model of its physical and chemical interactions with bacteria and parasitic nematodes in its tissues. Combining MSI and microCT, we introduce a workflow to connect metabolic and anatomic phenotypes of small symbiotic animals that often represent keystone species for ecosystem-functioning. SignificanceMetabolites mediate the establishment and persistence of most inter-kingdom symbioses. Still, to pinpoint the metabolites each partner displays upon interaction remains the biggest challenge in studying multi-organismal assemblages. Addressing this challenge, we developed a correlative imaging workflow to connect the in situ production of metabolites with the organ-scale and cellular 3D distributions of mutualistic and pathogenic (micro)organisms in the same host animal. Combining mass spectrometry imaging and micro-computed X-ray tomography provided a culture-independent approach, which is essential to include the full spectrum of naturally occurring interactions. To introduce the potential of combining high-resolution tomography with metabolite imaging, we resolve the metabolic interactions between an invertebrate host, its symbiotic bacteria and tissue parasites at unprecedented detail for model and non-model symbioses.

ecology↗

bioRxiv2019

Seagrass excretes sugars to their rhizosphere making them the sweet spots in the sea

Seagrasses are one of the most efficient sinks of carbon dioxide on Earth1: They bury carbon 35 times faster than tropical rainforests on a per unit area basis2. While we know that carbon sequestration in terrestrial plants is intimately linked to the microorganisms living in their soils3-6, the interactions of seagrasses with their rhizospheres are poorly understood. We show that three seagrass species from two oceans excrete simple sugars, mainly sucrose, into their rhizosphere that accumulate to over 200 {micro}M. Such high concentrations are at least 80 times higher than previously observed in the ocean, and surprising, as sugars are quickly consumed by microorganisms. In situ analyses and incubation experiments indicated that phenolic compounds from the seagrass inhibited microbial consumption of sucrose. Metagenomic and metatranscriptomic analyses of the microbial communities in the seagrass rhizosphere revealed that many members had the genes for degrading sucrose, but these were only expressed by a few specialists that also expressed genes for degrading phenolics. Our results explain why sucrose accumulates under seagrass meadows, where it comprises as much as 40% of the dissolved organic carbon. Destruction of extant seagrass canopies would allow sediment microorganisms to consume the tremendous deposits of sucrose buried underneath their meadows, thereby releasing large amounts of CO2 into the oceans and atmosphere.

microbiology↗

bioRxiv2018

Evaluating an Upper Respiratory Disease Panel on the Portable MinION Sequencer

The MinION was used to evaluate upper respiratory disease infections using both whole genome amplification (WGA), targeted sequencing, and was found to have tremendous potential for field use. The MinION nanopore sequencer was been released to community testers for evaluation using a variety of sequencing applications. The MinION was used to evaluate upper respiratory disease infections using both whole genome amplification and targeted sequencing, and was found to have tremendous potential for field use. In this study, we tested the ability of the MinION nanopore sequencer to accurately identify and differentiate clinical bacterial and viral samples via targeted sequencing and whole genome sequencing. The current nanopore technology has limitations with respect to error rate but has steadily improved with development of new flow cells and kits. Upper respiratory disease organisms were successfully identified and differentiated down to the strain level with 87-98% alignment to our reference genome database. The ability to differentiate strains by amplicon and whole genome sequencing on the MinION was accomplished despite the observed average per 100-base error rate averaged 1.2E-01. This study offers evidence of the utility of sequencing to identify and differentiate both viral and bacterial species present within clinical samples.

genomics↗