372 research outputs found
Cisternal Organization of the Endoplasmic Reticulum during Mitosis
The endoplasmic reticulum (ER) of animal cells is a single, dynamic, and continuous membrane network of interconnected cisternae and tubules spread out throughout the cytosol in direct contact with the nuclear envelope. During mitosis, the nuclear envelope undergoes a major rearrangement, as it rapidly partitions its membrane-bound contents into the ER. It is therefore of great interest to determine whether any major transformation in the architecture of the ER also occurs during cell division. We present structural evidence, from rapid, live-cell, three-dimensional imaging with confirmation from high-resolution electron microscopy tomography of samples preserved by high-pressure freezing and freeze substitution, unambiguously showing that from prometaphase to telophase of mammalian cells, most of the ER is organized as extended cisternae, with a very small fraction remaining organized as tubules. In contrast, during interphase, the ER displays the familiar reticular network of convolved cisternae linked to tubules
Electron cryotomography: a new view into microbial ultrastructure
Electron cryotomography (ECT) is an emerging technology that allows thin samples such as small bacterial cells to be imaged in 3D in a nearly native state to ‘molecular’ (not, vert, similar4 nm) resolution. As such, ECT is beginning to deliver long-awaited insight into the positions and structures of cytoskeletal filaments, cell wall elements, motility machines, chemoreceptor arrays, internal compartments, and other ultrastructures. Here we briefly explain ECT, review its recent contributions to microbiology, and conclude with a discussion of future prospects
Cross-membranes orchestrate compartmentalization and morphogenesis in Streptomyces
Microbial Biotechnolog
A gradient-forming MipZ protein mediating the control of cell division in the magnetotactic bacterium Magnetospirillum gryphiswaldense
Cell division needs to be tightly regulated and closely coordinated with other cellular processes to ensure the generation of fully viable offspring. Here, we investigate division site placement by the cell division regulator MipZ in the alphaproteobacterium Magnetospirillum gryphiswaldense, a species that forms linear chains of magnetosomes to navigate within the geomagnetic field. We show that M. gryphiswaldense contains two MipZ homologs, termed MipZ1 and MipZ2. MipZ2 localizes to the division site, but its absence does not cause any obvious phenotype. MipZ1, by contrast, forms a dynamic bipolar gradient, and its deletion or overproduction cause cell filamentation, suggesting an important role in cell division. The monomeric form of MipZ1 interacts with the chromosome partitioning protein ParB, whereas its ATP-dependent dimeric form shows non-specific DNA-binding activity. Notably, both the dimeric and, to a lesser extent, the monomeric form inhibit FtsZ polymerization in vitro. MipZ1 thus represents a canonical gradient-forming MipZ homolog that critically contributes to the spatiotemporal control of FtsZ ring formation. Collectively, our findings add to the view that the regulatory role of MipZ proteins in cell division is conserved among many alphaproteobacteria. However, their number and biochemical properties may have adapted to the specific needs of the host organism
Bond-Selective Intensity Diffraction Tomography
Recovering molecular information remains a grand challenge in the widely used
holographic and computational imaging technologies. To address this challenge,
we developed a computational mid-infrared photothermal microscope, termed
Bond-selective Intensity Diffraction Tomography (BS-IDT). Based on a low-cost
brightfield microscope with an add-on pulsed light source, BS-IDT recovers both
infrared spectra and bond-selective 3D refractive index maps from
intensity-only measurements. High-fidelity infrared fingerprint spectra
extraction is validated. Volumetric chemical imaging of biological cells is
demonstrated at a speed of ~20 seconds per volume, with a lateral and axial
resolution of ~350 nm and ~1.1 micron, respectively. BS-IDT's application
potential is investigated by chemically quantifying lipids stored in cancer
cells and volumetric chemical imaging on Caenorhabditis elegans with a large
field of view (~100 micron X 100 micron)
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