Biology subjects

Gaifas, L.

Publications and source records attributed to Gaifas, L..

5 recordsLinked to original sources

bioRxiv2026

Deinococcus radiodurans HU: a versatile architect of nucleoid structure and plasticity

Nucleoid-associated proteins are known to compact and organise bacterial genomes, but how their local DNA binding shapes higher-order chromatin architecture remains unclear. Using in vitro and in situ approaches, we investigated how Deinococcus radiodurans HU (DrHU) orchestrates nucleoid organisation. DrHU engages DNA through two synergistic binding modes: high-affinity {beta}-hairpin-mediated stabilisation of DNA loops and low-affinity, multivalent interaction via its N-terminal tail, driving parallel, uniformly spaced DNA alignment. In vitro, DrHU organises supercoiled plasmid DNA into regular 2D lattices of double-spirals, while in situ, UV-C light induces a nucleoid transition from a loose DNA mesh to a blue liquid crystalline phase characterised by DNA swirls. The striking structural similarity and shared inter-filament spacing of these two arrangements suggests that DrHU plays a pivotal role in genome organisation through its versatile binding properties that enable DNA loop stabilisation, protection and DNA bridging, linking molecular interactions to 3D genome ordering and stress-induced remodelling.

microbiology↗

bioRxiv2024

Combining live cell fluorescence imaging with in situ cryo electron tomography sheds light on the septation process in Deinococcus radiodurans

Cell division is a fundamental biological process that allows a single mother cell to produce two daughter cells. In bacteria, different modes of cell division have been reported that are notably associated with distinctive cell shapes, but in all cases, division involves a step of septation, corresponding to the growth of a new dividing cell wall, followed by splitting of the two daughter cells. The radiation-resistant Deinococcus radiodurans is a spherical bacterium protected by a thick and unusual cell envelope. It has been reported to divide using a distinctive mode of septation in which two septa originating from opposite sides of the cell progress with a flat leading edge until meeting and fusing at mid-cell. In the present study, we have combined conventional and super-resolution fluorescence microscopy of live bacteria with in situ cryogenic electron tomography of bacterial lamellae to investigate the septation process in D. radiodurans. This work provides important insight into (i) the complex architecture of the cell envelope of this bacterium, (ii) the sliding doors septation process and (iii) the molecular mechanisms underlying septal growth and closure.

microbiology↗

bioRxiv2024

Surforama: interactive exploration of volumetric data by leveraging 3D surfaces

MotivationVisualization and annotation of segmented surfaces is of paramount importance for studying membrane proteins in their native cellular environment by cryogenic electron tomography (cryo-ET). Yet, analyzing membrane proteins and their organization is challenging due to their small sizes and the need to consider local context constrained to the membrane surface. ResultsTo interactively visualize, annotate, and analyze proteins in cellular context from cryo-ET data, we have developed Surforama, a Python package and napari plugin. For interactive visualization of membrane proteins in tomograms, Surforama renders the local densities projected on the surface of the segmentations. Suforama additionally provides tools to annotate and analyze particles on the membrane surfaces. Finally, for compatibility with other tools in the cryo-ET analysis ecosystem, results can be exported as RELION-formatted STAR files. As a demonstration, we performed subtomogram averaging and neighborhood analysis of photosystem II proteins in thylakoid membranes from the green alga Chlamydomonas reinhardtii. Availability and implementationPython package, code and examples are available at: https://github.com/cellcanvas/surforama

bioinformatics↗

bioRxiv2023

blik: an extensible napari plugin for cryo-ET data visualisation, annotation and analysis

Powerful, workflow-agnostic and interactive visualisation is essential for the ad-hoc, human-in-the-loop workflows typical of cryo-electron tomography (cryo-ET). While several tools exist for visualisation and annotation of cryo-ET data, they are often integrated as part of monolithic processing pipelines, or focused on a specific task and offering limited reusability and extensibility. With each software suite presenting its own pros and cons and often tools tailored to address specific challenges, seamless integration between available pipelines is often a difficult task. As part of the effort to enable such flexibility and move the software ecosystem towards a more collaborative and modular approach, we developed blik, an open-source napari plugin for visualisation and annotation of cryo-ET data (source code: https://github.com/brisvag/blik). blik offers fast, interactive, and user-friendly 3D visualisation thanks to napari, and is built with extensibility and modularity at the core. Data is handled and exposed through well-established scientific Python libraries such as numpy arrays and pandas dataframes. Reusable components (such as data structures, file read/write, and annotation tools) are developed as independent Python libraries to encourage reuse and community contribution. By easily integrating with established image analysis tools - even outside of the cryo-ET world - blik provides a versatile platform for interacting with cryo-ET data. On top of core visualisation features - interactive and simultaneous visualisation of tomograms, particle picks and segmentations - blik provides an interface for interactive tools such as manual particle picking, surface-based and filament-based particle picking and image segmentation, as well as simple filtering tools. Additional self-contained napari plugins developed as part of this work also implement interactive plotting and selection based on particle features, and label interpolation for easier segmentation. Finally, we highlight the differences with existing software and showcase bliks applicability in biological research.

bioinformatics↗

bioRxiv2021

Tools enabling flexible approaches to high-resolution subtomogram averaging

Cryo-electron tomography and subtomogram averaging are increasingly used for macromolecular structure determination in situ. Here we introduce a set of computational tools and resources designed to enable flexible approaches to subtomogram averaging. In particular, our tools simplify metadata handling, increase automation, and interface the Dynamo software package with the Warp-Relion-M pipeline. We provide a framework for ab initio and geometrical approaches to subtomogram averaging combining tools from these packages. We illustrate the power of working within the framework enabled by our developments by applying it to EMPIAR-10164, a publicly available dataset containing immature HIV-1 virus-like particles, and a challenging in situ dataset containing chemosensory arrays in bacterial minicells. Additionally, we establish an open and collaborative online platform for sharing knowledge and tools related to cryo-electron tomography data processing. To this platform, we contribute a comprehensive guide to obtaining state-of-the-art results from EMPIAR-10164.

biophysics↗