Andriko von Kügelgen, C. Keith Cassidy, Sofie van Dorst, Lennart L. Pagani, Christopher Batters, Zephyr Ford, Jan Löwe, Vikram Alva, Phillip J. Stansfeld & Tanmay A. M. Bharat

Nitrosopumilus maritimus is an ammonia-oxidizing archaeon that is crucial to the global nitrogen cycle. A critical step for nitrogen oxidation is the entrapment of ammonium ions from a dilute marine environment at the cell surface and their subsequent channelling to the cell membrane of N. maritimus. Here we elucidate the structure of the molecular machinery responsible for this process, comprising the surface layer (S-layer), using electron cryotomography and subtomogram averaging from cells. We supplemented our in situ structure of the ammonium-binding S-layer array with a single-particle electron cryomicroscopy structure, revealing detailed features of this immunoglobulin-rich and glycan-decorated S-layer. This in situ structural study illuminates the biogeochemically essential process of ammonium binding and channelling, common to many marine microorganisms that are fundamental to the nitrogen cycle.

Nature. May 2024

Ulyana Lalo, Yuriy Pankratov

Intracellular Ca²⁺-signaling in astrocytes is instrumental for their brain “housekeeping” role and astroglial control of synaptic plasticity. An important source for elevating the cytosolic Ca²⁺ level in astrocytes is a release from endoplasmic reticulum which can be triggered via two fundamental pathways: IP3 receptors and calcium-induced calcium release (CICR) mediated by Ca²⁺-sensitive ryanodine receptors (RyRs). We explored the role for ryanodine receptors in the modulation of cytosolic Ca²⁺-signaling in the cortical and hippocampal astrocytes, astrocyte-neuron communication and astroglia modulation of synaptic plasticity. Our data demonstrate that ryanodine receptors are essential for astrocytic Ca²⁺-signaling and efficient astrocyte-neuron communications. The RyR-mediated CICR contributes to astrocytic control of synaptic plasticity and can underlie, at least partially, neuroprotective and cognitive effects of caffein.

Frontiers in Cellular Neuroscience. May 2024

Ane Landajuela, Martha Braun, Christopher D.A. Rodrigues, Erdem Karatekin

Membrane fission is an essential process in all domains of life. The underlying mechanisms remain poorly understood in bacteria, partly because suitable assays are lacking. Here, we describe an assay to detect membrane fission during endospore formation in single Bacillus subtilis cells with a temporal resolution of ∼1 min. Other cellular processes can be quantified and temporally aligned to the membrane fission event in individual cells, revealing correlations and causal relationships.

STAR Protocols. March 2024

Kevin D. Whitley, James Grimshaw, David M. Roberts, Eleni Karinou, Phillip J. Stansfeld & Seamus Holden

Bacterial cell division requires septal peptidoglycan (sPG) synthesis by the divisome complex. Treadmilling of the essential tubulin homologue FtsZ has been implicated in septal constriction, though its precise role remains unclear. Here we used live-cell single-molecule imaging of the divisome transpeptidase PBP2B to investigate sPG synthesis dynamics in Bacillus subtilis. In contrast to previous models, we observed a single population of processively moving PBP2B molecules whose motion is driven by peptidoglycan synthesis and is not associated with FtsZ treadmilling. However, despite the asynchronous motions of PBP2B and FtsZ, a partial dependence of PBP2B processivity on FtsZ treadmilling was observed. Additionally, through single-molecule counting experiments we provide evidence that the divisome synthesis complex is multimeric. Our results support a model for B. subtilis division where a multimeric synthesis complex follows a single track dependent on sPG synthesis whose activity and dynamics are asynchronous with FtsZ treadmilling.

Nature Microbiology. March 2024

Talal Al-Yazeedi, Sally Adams, Sophie Tandonnet, Anisa Turner, Jun Kim, Junho Lee, Andre Pires-daSilva

Auanema freiburgense is a nematode with males, females, and selfing hermaphrodites. When XO males mate with XX females, they typically produce a low proportion of XO offspring because they eliminate nullo-X spermatids. This occurs because of an unequal distribution of essential cellular organelles during sperm formation. Intriguingly, the interbreeding of two A. freiburgense strains results in hybrid males capable of producing viable nullo-X sperm. Consequently, when these hybrid males mate with females, they yield a high percentage of male offspring. To uncover the genetic basis of nullo-spermatid elimination and X- chromosome drive, we generated a genome assembly for A. freiburgense, and genotyped the intercrossed lines. This analysis identified a Quantitative Trait Locus spanning several X chromosome genes linked to the non-Mendelian inheritance patterns observed in A. freiburgense. This finding provides valuable clues to the underlying factors involved in asymmetric organelle partitioning during male meiotic division and thus non-Mendelian transmission of the X chromosome and sex ratios.

Genetics. March 2024

Javier Sánchez Romano, Jaione Simón-Santamaria, Peter McCourt, Bård Smedsrød, Kim Erlend Mortensen, Antonia P. Sagona, Karen Kristine Sørensen, Anett Kristin Larsen

Blood-borne phages are believed to be captured by macrophages in the liver and spleen. Since liver sinusoids also consist of specialized scavenger liver sinusoidal endothelial cells (LSECs) and Kupffer cells (KCs), this study investigated the contribution of both cell types in the elimination of Escherichia coli phage K1Fg10b::gfp (K1F^gfp) in mice. The results presented herein contribute to increased knowledge about the pharmacokinetics of the T7-like phage K1F in the mammalian system. The cell types of the liver that are responsible for rapid phage blood clearance are identified. Our results highlight the need for more research about appropriate dose regimens when phage therapy is delivered intravenously and advise essential knowledge about cell systems that should be investigated further for detailed phage pharmacodynamics.

mSphere. February 2024