FtsZ induces membrane deformations via torsional stress upon GTP hydrolysis

Osawa M., Erickson H.P.

L form bacteria do not have a cell wall and are thought to require medium of high osmolality for survival and growth. In this study we tested whether L forms can adapt to growth in lower osmolality medium. We first tested the Escherichia coli L form NC-7, generated in 1987 by Onoda following heavy mutagenesis. We started with growth in osmoprotective medium (~ 764 mOsm kg–1) and diluted it stepwise into medium of lower osmolality. At each step the cells were given up to 10 days to adapt and begin growing, during which they apparently acquired multiple new mutations. We eventually obtained a strain that could grow in LB containing only 34 mM NaCl, 137 mOsm kg–1 total. NC-7 showed a variety of morphologies including spherical, angular and cylindrical cells. Some cells extruded a bud that appeared to be the outer membrane enclosing an enlarged periplasm. Additional evidence for an outer membrane was sensitivity of the cells to the compound CHIR-090, which blocks the LPS pathway, and to EDTA which chelates Mg that may stabilize and rigidify the LPS in the outer membrane. We suggest that the mechanical rigidity of the outer membrane enables the angular shapes and provides some resistance to turgor in the low-osmolality media. Interestingly, cells that had an elongated shape underwent division shortly after addition of EDTA, suggesting that reducing the rigidity of the outer membrane under some turgor pressure induces division before lysis occurs. We then tested a well-characterized L form from Bacillus subtilis . L form strain LR-2L grew well with sucrose at 1246 and 791 mOsm kg–1. It survived when diluted directly into 440 mOsm kg–1 but grew poorly, achieving only 1/10 to 1/5 the density. The B. subtilis L form apparently adapted to this direct dilution by rapidly reducing cytoplasmic osmolality.

Pannuzzo M., McDargh Z.A., Deserno M.

The large GTPase dynamin catalyzes membrane fission in eukaryotic cells, but despite three decades of experimental work, competing and partially conflicting models persist regarding some of its most basic actions. Here we investigate the mechanical and functional consequences of dynamin scaffold shape changes and disassembly with the help of a geometrically and elastically realistic simulation model of helical dynamin-membrane complexes. Beyond changes of radius and pitch, we emphasize the crucial role of a third functional motion: an effective rotation of the filament around its longitudinal axis, which reflects alternate tilting of dynamin’s PH binding domains and creates a membrane torque. We also show that helix elongation impedes fission, hemifission is reached via a small transient pore, and coat disassembly assists fission. Our results have several testable structural consequences and help to reconcile mutual conflicting aspects between the two main present models of dynamin fission—the two-stage and the constrictase model.

Krupka M., Sobrinos-Sanguino M., Jiménez M., Rivas G., Margolin W.

ABSTRACT ZipA is an essential cell division protein in Escherichia coli . Together with FtsA, ZipA tethers dynamic polymers of FtsZ to the cytoplasmic membrane, and these polymers are required to guide synthesis of the cell division septum. This dynamic behavior of FtsZ has been reconstituted on planar lipid surfaces in vitro , visible as GTP-dependent chiral vortices several hundred nanometers in diameter, when anchored by FtsA or when fused to an artificial membrane binding domain. However, these dynamics largely vanish when ZipA is used to tether FtsZ polymers to lipids at high surface densities. This, along with some in vitro studies in solution, has led to the prevailing notion that ZipA reduces FtsZ dynamics by enhancing bundling of FtsZ filaments. Here, we show that this is not the case. When lower, more physiological levels of the soluble, cytoplasmic domain of ZipA (sZipA) were attached to lipids, FtsZ assembled into highly dynamic vortices similar to those assembled with FtsA or other membrane anchors. Notably, at either high or low surface densities, ZipA did not stimulate lateral interactions between FtsZ protofilaments. We also used E. coli mutants that are either deficient or proficient in FtsZ bundling to provide evidence that ZipA does not directly promote bundling of FtsZ filaments in vivo . Together, our results suggest that ZipA does not dampen FtsZ dynamics as previously thought, and instead may act as a passive membrane attachment for FtsZ filaments as they treadmill. IMPORTANCE Bacterial cells use a membrane-attached ring of proteins to mark and guide formation of a division septum at midcell that forms a wall separating the two daughter cells and allows cells to divide. The key protein in this ring is FtsZ, a homolog of tubulin that forms dynamic polymers. Here, we use electron microscopy and confocal fluorescence imaging to show that one of the proteins required to attach FtsZ polymers to the membrane during E. coli cell division, ZipA, can promote dynamic swirls of FtsZ on a lipid surface in vitro . Importantly, these swirls are observed only when ZipA is present at low, physiologically relevant surface densities. Although ZipA has been thought to enhance bundling of FtsZ polymers, we find little evidence for bundling in vitro . In addition, we present several lines of in vivo evidence indicating that ZipA does not act to directly bundle FtsZ polymers.

Holden S.

Bacterial cell division takes place almost entirely below the diffraction limit of light microscopy, making super-resolution microscopy ideally suited to interrogating this process. I review how super-resolution microscopy has advanced our understanding of bacterial cell division. I discuss the mechanistic implications of these findings, propose physical models for cell division compatible with recent data, and discuss key outstanding questions and future research directions.

Ramirez-Diaz D.A., García-Soriano D.A., Raso A., Mücksch J., Feingold M., Rivas G., Schwille P.

FtsZ, the primary protein of the bacterial Z ring guiding cell division, has been recently shown to engage in intriguing treadmilling dynamics along the circumference of the division plane. When coreconstituted in vitro with FtsA, one of its natural membrane anchors, on flat supported membranes, these proteins assemble into dynamic chiral vortices compatible with treadmilling of curved polar filaments. Replacing FtsA by a membrane-targeting sequence (mts) to FtsZ, we have discovered conditions for the formation of dynamic rings, showing that the phenomenon is intrinsic to FtsZ. Ring formation is only observed for a narrow range of protein concentrations at the bilayer, which is highly modulated by free Mg2+ and depends upon guanosine triphosphate (GTP) hydrolysis. Interestingly, the direction of rotation can be reversed by switching the mts from the C-terminus to the N-terminus of the protein, implying that the filament attachment must have a perpendicular component to both curvature and polarity. Remarkably, this chirality switch concurs with previously shown inward or outward membrane deformations by the respective FtsZ mutants. Our results lead us to suggest an intrinsic helicity of FtsZ filaments with more than one direction of curvature, supporting earlier hypotheses and experimental evidence.

Osawa M., Erickson H.P.

Bacterial cytokinesis begins with the assembly of FtsZ into a Z ring at the center of the cell. The Z-ring constriction in Gram-negative bacteria may occur in an environment where the periplasm and the cytoplasm are isoosmotic, but in Gram-positive bacteria the constriction may have to overcome a substantial turgor pressure. We address three potential sources of invagination force. (1) FtsZ itself may generate force by curved protofilaments bending the attached membrane. This is sufficient to constrict liposomes in vitro. However, this force is on the order of a few pN, and would not be enough to overcome turgor. (2) Cell wall (CW) synthesis may generate force by pushing the plasma membrane from the outside. However, this would probably require some kind of Brownian ratchet to separate the CW and membrane sufficiently to allow a glycan strand to slip in. The elastic element is not obvious. (3) Excess membrane production has the potential to contribute significantly to the invagination force. If the excess membrane is produced under the CW, it would force the membrane to bleb inward. We propose here that a combination of FtsZ pulling from the inside, and excess membrane pushing membrane inward may generate a substantial constriction force at the division site. This combined force generation mechanism may be sufficient to overcome turgor pressure. This would abolish the need for a Brownian ratchet for CW growth, and would permit CW to operate by reinforcing the constrictions generated by FtsZ and excess membrane.

Takeda T., Kozai T., Yang H., Ishikuro D., Seyama K., Kumagai Y., Abe T., Yamada H., Uchihashi T., Ando T., Takei K.

Dynamin is a mechanochemical GTPase essential for membrane fission during clathrin-mediated endocytosis. Dynamin forms helical complexes at the neck of clathrin-coated pits and their structural changes coupled with GTP hydrolysis drive membrane fission. Dynamin and its binding protein amphiphysin cooperatively regulate membrane remodeling during the fission, but its precise mechanism remains elusive. In this study, we analyzed structural changes of dynamin-amphiphysin complexes during the membrane fission using electron microscopy (EM) and high-speed atomic force microscopy (HS-AFM). Interestingly, HS-AFM analyses show that the dynamin-amphiphysin helices are rearranged to form clusters upon GTP hydrolysis and membrane constriction occurs at protein-uncoated regions flanking the clusters. We also show a novel function of amphiphysin in size control of the clusters to enhance biogenesis of endocytic vesicles. Our approaches using combination of EM and HS-AFM clearly demonstrate new mechanistic insights into the dynamics of dynamin-amphiphysin complexes during membrane fission.

Colom A., Redondo-Morata L., Chiaruttini N., Roux A., Scheuring S.

Significance The GTPase dynamin catalyzes membrane fission and is essential in endocytosis and other events such as organelle division. Dynamin is a unique molecular motor with torsional and contractile abilities. Because these abilities involve a conformational change at the whole-polymer level, standard structural biology tools have not been able to fully unravel the mechanism by which it constricts and twists. Here we used high-speed atomic force microscopy to image the constriction and fission of dynamin-coated tubules with subnanometer and subsecond resolution. Our results provide important findings to establish the contribution of the various constriction mechanisms.

Yang X., Lyu Z., Miguel A., McQuillen R., Huang K.C., Xiao J.

Coordinating cell wall synthesis and cell division Most bacteria are protected by peptidoglycan cell walls, which must be remodeled to split the cell. Cell division requires the tubulin homolog FtsZ, a highly conserved cytoskeletal polymer that specifies the future site of division. Bisson-Filho et al. and Yang et al. found that the dynamic treadmilling of FtsZ filaments controls both the location and activity of the associated cell wall synthetic enzymes. This creates discrete sites of cell wall synthesis that circle around the division plane to divide the cell. Science , this issue p. 739 , p. 744

Bisson-Filho A.W., Hsu Y., Squyres G.R., Kuru E., Wu F., Jukes C., Sun Y., Dekker C., Holden S., VanNieuwenhze M.S., Brun Y.V., Garner E.C.

Coordinating cell wall synthesis and cell division Most bacteria are protected by peptidoglycan cell walls, which must be remodeled to split the cell. Cell division requires the tubulin homolog FtsZ, a highly conserved cytoskeletal polymer that specifies the future site of division. Bisson-Filho et al. and Yang et al. found that the dynamic treadmilling of FtsZ filaments controls both the location and activity of the associated cell wall synthetic enzymes. This creates discrete sites of cell wall synthesis that circle around the division plane to divide the cell. Science , this issue p. 739 , p. 744

Coltharp C., Xiao J.

We propose that the essential function of the most highly conserved protein in bacterial cytokinesis, FtsZ, is not to generate a mechanical force to drive cell division. Rather, we suggest that FtsZ acts as a signal-processing hub to coordinate cell wall synthesis at the division septum with a diverse array of cellular processes, ensuring that the cell divides smoothly at the correct time and place, and with the correct septum morphology. Here, we explore how the polymerization properties of FtsZ, which have been widely attributed to force generation, can also be advantageous in this signal processing role. We suggest mechanisms by which FtsZ senses and integrates both mechanical and biochemical signals, and conclude by proposing experiments to investigate how FtsZ contributes to the remarkable spatial and temporal precision of bacterial cytokinesis.

Fierling J., Johner A., Kulić I.M., Mohrbach H., Müller M.M.

We study the deformations of a fluid membrane imposed by adhering stiff bio-filaments due to the torques they apply. In the limit of small deformations, we derive a general expression for the energy and the deformation field of the membrane. This expression is specialised to different important cases including closed and helical bio-filaments. In particular, we analyse interface-mediated interactions and membrane wrapping when the filaments apply a local torque distribution on a tubular membrane.

Szwedziak P., Wang Q., Bharat T.A., Tsim M., Löwe J.

Membrane constriction is a prerequisite for cell division. The most common membrane constriction system in prokaryotes is based on the tubulin homologue FtsZ, whose filaments in E. coli are anchored to the membrane by FtsA and enable the formation of the Z-ring and divisome. The precise architecture of the FtsZ ring has remained enigmatic. In this study, we report three-dimensional arrangements of FtsZ and FtsA filaments in C. crescentus and E. coli cells and inside constricting liposomes by means of electron cryomicroscopy and cryotomography. In vivo and in vitro, the Z-ring is composed of a small, single-layered band of filaments parallel to the membrane, creating a continuous ring through lateral filament contacts. Visualisation of the in vitro reconstituted constrictions as well as a complete tracing of the helical paths of the filaments with a molecular model favour a mechanism of FtsZ-based membrane constriction that is likely to be accompanied by filament sliding.

Broedersz C. ., MacKintosh F. .

Here, we provide an overview of theoretical approaches to semiflexible polymers and their networks. Such semiflexible polymers have large bending rigidities that can compete with the entropic tendency of a chain to crumple up into a random coil. Many studies on semiflexible polymers and their assemblies have been motivated by their importance in biology. Indeed, crosslinked networks of semiflexible polymers form a major structural component of tissue and living cells. Reconstituted networks of such biopolymers have emerged as a new class of biological soft matter systems with remarkable material properties, which have spurred many of the theoretical developments discussed here. Starting from the mechanics and dynamics of individual semiflexible polymers, we review the physics of semiflexible bundles, entangled solutions and disordered cross-linked networks. Finally, we discuss recent developments on marginally stable fibrous networks, which exhibit critical behavior similar to other marginal systems such as jammed soft matter.

Bassereau P., Sorre B., Lévy A.

Current description of biomembrane mechanics originates for a large part from W. Helfrich's model. Based on his continuum theory, many experiments have been performed in the past four decades on simplified membranes in order to characterize the mechanical properties of lipid membranes and the contribution of polymers or proteins. The long-term goal was to develop a better understanding of the mechanical properties of cell membranes. In this paper, we will review representative experimental approaches that were developed during this period and the main results that were obtained.

Aguilar-Maldonado A., Monroy F., Santiago J.A.

Catenoid necks, as minimal surfaces with zero mean curvature (K=0), minimize bending energy and serve as geometric scaffolds for scissional membrane remodeling. We apply the Canham–Helfrich model of flexible membranes to analyze deformable spontaneous curvature (K0), a key regulator of membrane scission events in cellular compartmentalization. To model functional membrane necking, we examine deformed catenoidal shapes with variable mean curvature (δK≠0) near the minimal-energy catenoid (K=0), which varies along either the constrictional or elongational pathways. Using the Euler–Lagrange equilibrium equations, we derive inhomogeneous catenoid solutions, revealing metastable singularities departing from the critical catenoid of the maximal area—a tipping point (TP) for scission. Using functional second-derivative analysis, we further examine how inhomogeneous K0 affects stability. The transition between frustrated constriction and abscissional elongation is numerically analyzed through conformal solutions to the governing inhomogeneous K0− field.

Kasai T., Tahara Y.O., Miyata M., Shiomi D.

Kumar R., Srinivasan R., Chaudhuri D.

The tubulinlike protein FtsZ (filamenting temperature-sensitive mutant Z) is crucial for cytokinesis in bacteria and many archaea, forming a ring-shaped structure called the Z-ring at the site of cell division. Despite extensive research, the self-assembly of Z-rings is not entirely understood. We propose a theoretical model based on FtsZ's known filament structures, treating them as semiflexible polymers with specific mechanical properties and lateral intersegment attraction that can stabilize ring formations. Our molecular dynamics simulations reveal various morphological phases, including open helices, chains, rings, and globules, capturing experimental observations in the fission yeast model using FtsZ from different bacterial species or mutants of . Using our theoretical model, we explore how treadmilling activity affects Z-ring stability and identify a spooling mechanism of ring formation. The active ring produces contractile, shear, and rotational stresses, which intensify as the Z-ring transitions to an open helix at high activity. Published by the American Physical Society 2025

Choudhury J., Chaudhuri B.N.

ABSTRACTZ‐ring formation by FtsZ, the master assembler of the divisome, is a key step in bacterial cell division. Membrane anchoring of the Z‐ring requires the assistance of dedicated Z‐ring binding proteins, such as SepF and FtsA. SepF participates in bundling and membrane anchoring of FtsZ in gram‐positive bacteria. We report in vitro biophysical studies of the interactions between FtsZ and a cytoplasmic component of cognate SepF from three different bacteria: Mycobacterium tuberculosis, Staphylococcus aureus, and Enterococcus gallinarum. While the cytosolic domain of SepF from M. tuberculosis is primarily a dimer, those from S. aureus and E. gallinarum polymerize to form ring‐like structures. Mycobacterial SepF helps in the bundling of FtsZ filaments to form thick filaments and large spirals. On the other hand, ring‐forming SepF from the Firmicutes bundle FtsZ into tubules. Our results suggest that the oligomeric form of SepF directs how it bundles FtsZ filaments.

Zhang Y., Lillo J.V., Mohamed Abdelrasoul M.S., Wang Y., Arrasate P., Frolov V.A., Noy A.

Dynamin 1 (Dyn1) GTPase, a principal driver of membrane fission during synaptic endocytosis, self-assembles into short mechanoactive helices cleaving the necks of endocytic vesicles. While structural information about Dyn1 helix is abundant, little is known about the nanoscale dynamics of the helical scaffolding at the moment of fission, complicating mechanistic understanding of Dyn1 action. To address the role of the helix dynamics in fission, we used High-Speed Atomic Force Microscopy (HS-AFM) and fluorescence microscopy to track and compare the spatiotemporal characteristics of the helices formed by wild-type Dyn1 and its K44A mutant impaired in GTP hydrolysis on minimal lipid membrane templates. In the absence of nucleotide, membrane-bound WT Dyn1 and K44A Dyn1 self-assembled into tubular protein scaffolding of similar diameter encaging the lipid bilayer. In both cases, the GTP addition caused scaffold constriction coupled with formation of 20 to 30 nm nanogaps in the protein coverage. While both proteins reached scaffold diameters characteristic for membrane superconstriction causing fission, the fission was detected only with WT Dyn1. We associated the fission activity with the dynamic evolution of the nanogaps: K44A Dyn1 gaps were static, while WT Dyn1 gaps actively evolved via repetitive nonaxisymmetric constriction-bending deformations caused by localized GTP hydrolysis. Modeling of the deformations implicated filament twist as an additional deformation mode which combines with superconstriction to facilitate membrane fission. Our results thus show that the dynamics of the Dyn1 helical scaffold goes beyond radial constriction and involves nonaxisymmetric deformations, where filament twist emerges as a critical driver of membrane fission.

Kasai T., Tahara Y.O., Miyata M., Shiomi D.

AbstractThe FtsZ protein is involved in bacterial cell division. In cell-walled bacteria, such asBacillus subtilis, FtsZ forms a ring-like structure, called the Z ring, at the cell division site and acts as a scaffold for cell wall synthesis. The inhibition of cell wall synthesis inB. subtilishas been shown to interfere with the function of the Z ring, causing a loss in cell division control.Spiroplasma, a cell wall-less bacterium, lacks most of the genes involved in cell division; however, theftsZgene remains conserved. The function ofSpiroplasma eriocheirisFtsZ (SeFtsZ) remains to be determined. In the present study, we analyzed the biochemical characteristics of SeFtsZ. Purified SeFtsZ demonstrated lower polymerization capacity and GTPase activity than FtsZ fromE. coliandB. subtilis. We also investigated the relationship between SeFtsZ and SeSepF, which anchors FtsZ to the cell membrane, and found that SeSepF did not contribute to the stability of FtsZ filaments, unlike theB. subtilisSepF. SeFtsZ and SeSepF were produced inE. coliL-forms, where cell wall synthesis was inhibited. SeFtsZ formed ring-like structures in cell wall-lessE. colicells, suggesting that SeFtsZ forms Z rings and is involved in cell division independently of cell wall synthesis.

de Brevern A.G.

The 3D protein structure is the basis for all their biological functions [...]

Knapp B.D., Shi H., Huang K.C.

The key bacterial cell division protein FtsZ can adopt multiple conformations, and prevailing models suggest that transitions of FtsZ subunits from the closed to open state are necessary for filament formation and stability. Using all-atom molecular dynamics simulations, we analyzed state transitions of Staphylococcus aureus FtsZ as a monomer, dimer, and hexamer. We found that monomers can adopt intermediate states but preferentially adopt a closed state that is robust to forced reopening. Dimer subunits transitioned between open and closed states, and dimers with both subunits in the closed state remained highly stable, suggesting that open-state conformations are not necessary for filament formation. Mg2+ strongly stabilized the conformation of GTP-bound subunits and the dimer filament interface. Our hexamer simulations indicate that the plus end subunit preferentially closes and that other subunits can transition between states without affecting inter-subunit stability. We found that rather than being correlated with subunit opening, inter-subunit stability was strongly correlated with catalytic site interactions. By leveraging deep-learning models, we identified key intrasubunit interactions governing state transitions. Our findings suggest a greater range of possible monomer and filament states than previously considered and offer new insights into the nuanced interplay between subunit states and the critical role of nucleotide hydrolysis and Mg2+ in FtsZ filament dynamics.

Curtis Z., Escudeiro P., Mallon J., Leland O., Rados T., Dodge A., Andre K., Kwak J., Yun K., Isaac B., Martinez Pastor M., Schmid A.K., Pohlschroder M., Alva V., Bisson A.

Bactofilins are rigid, nonpolar bacterial cytoskeletal filaments that link cellular processes to specific curvatures of the cytoplasmic membrane. Although homologs of bactofilins have been identified in archaea and eukaryotes, functional studies have remained confined to bacterial systems. Here, we characterize representatives of two families of archaeal bactofilins from the pleomorphic archaeon Haloferax volcanii , halofilin A (HalA) and halofilin B (HalB). HalA and HalB polymerize in vitro, assembling into straight bundles. HalA polymers are highly dynamic and accumulate at positive membrane curvatures in vivo, whereas HalB forms more static foci that localize in areas of local negative curvatures on the outer cell surface. Gene deletions and live-cell imaging show that halofilins are critical in maintaining morphological integrity during shape transition from disk (sessile) to rod (motile). Morphological defects in Δ halA result in accumulation of highly positive curvatures in rods but not in disks. Conversely, disk-shaped cells are exclusively affected by halB deletion, resulting in flatter cells. Furthermore, while Δ halA and Δ halB cells imprecisely determine the future division plane, defects arise predominantly during the disk-to-rod shape remodeling. The deletion of halA in the haloarchaeon Halobacterium salinarum , whose cells are consistently rod-shaped, impacted morphogenesis but not cell division. Increased levels of halofilins enforced drastic deformations in cells devoid of the S-layer, suggesting that HalB polymers are more stable at defective S-layer lattice regions. Our results suggest that halofilins might play a significant mechanical scaffolding role in addition to possibly directing envelope synthesis.

Li F., Yu H., Zhang B., Hu C., Lan F., Wang Y., You Z., Liu Q., Tang R., Zhang J., Li C., Shi L., Li W., Nealson K.H., Liu Z., et. al.

AbstractTo investigate how cell elongation impacts extracellular electron transfer (EET) of electroactive microorganisms (EAMs), the division of model EAM Shewanella oneidensis (S. oneidensis) MR‐1 is engineered by reducing the formation of cell divisome. Specially, by blocking the translation of division proteins via anti‐sense RNAs or expressing division inhibitors, the cellular length and output power density are all increased. Electrophysiological and transcriptomic results synergistically reveal that the programmed cell elongation reinforces EET by enhancing NADH oxidation, inner‐membrane quinone pool, and abundance of c‐type cytochromes. Moreover, cell elongation enhances hydrophobicity due to decreased cell‐surface polysaccharide, thus facilitates the initial surface adhesion stage during biofilm formation. The output current and power density all increase in positive correction with cellular length. However, inhibition of cell division reduces cell growth, which is then restored by quorum sensing‐based dynamic regulation of cell growth and elongation phases. The QS‐regulated elongated strain thus enables a cell length of 143.6 ± 40.3 µm (72.6‐fold of that of S. oneidensis MR‐1), which results in an output power density of 248.0 ± 10.6 mW m−2 (3.41‐fold of that of S. oneidensis MR‐1) and exhibits superior potential for pollutant treatment. Engineering cellular length paves an innovate avenue for enhancing the EET of EAMs.

Yu H., Lan F., Hu C., You Z., Dai L., Zhang B., Liu Q., Xiong B., Shi L., Liu Z., Li F., Song H.

The slow rate of extracellular electron transfer (EET) of electroactive microorganisms (EAMs) remains a predominate bottleneck that restricts practical applications of bio-electrochemical systems. Cell division has significant effects on cell cycle, morphology, growth and metabolism. However, the relation between cell division and the EET rate of Shewanella oneidensis has not been established. Here, we employed modular engineering strategy to accelerate DNA replication in the C period and divisome formation in the D period of cell cycle, which decreased cellular volume and enhanced the EET efficiency. Assembly of the C and D period modules further decreased the cell volume by 82.0 % and enhanced power density by 3.12-fold. Electrophysiological and transcriptomic analyses synergistically revealed that the programmed cell volume decrease facilitated lactate uptake and cellular metabolism due to the increased specific surface area (SSA), which consequently reinforced intracellular electron generation. Moreover, the reduced cell size facilitated electroactive biofilm formation. Furthermore, programmed increase in riboflavin biosynthesis and transport further strengthened indirect EET and boosted output power density to 1537.8 ± 116.9 mW m−2, 21.1-fold of that of the WT. The engineered strains exhibited superior abilities for Cr6+ reduction and azo dyes degradation. This study shed light on the underlying mechanism how reduced cell size impacts electrophysiology of EAMs, and indicated accelerating cell division is a promising avenue to increase the EET of EAMs for efficient environmental pollution treatment.

Zhang J., Xu X., Liu F., Cao S., Gui Y., Su Y., He X., Liang J., Zou Y.

Aggregate-induced emission luminogens (AIEgens) have been widely used in biological imaging, chemical sensing, and disease treatments. The rational design and construction of AIEgens have received considerable research interests during the last few years. Herein, molecular docking-aided AIEgen design has been reasonably proposed and AIEgen TBQZY with excellent 1O2 generation ability has been synthesized. The newly developed TBQZY could efficiently kill S. epidermidis and methicillin-resistant S. epidermidis (MRSE) by tightly binding to bacteria and triggering the accumulation of 1O2 in bacteria. TBQZY specifically regulated the immune system and polarized macrophages from M1 to M2 to accelerate the elimination of biofilm in vivo. In addition, healing acceleration was observed in chronic wounds treated with TBQZY, and side effects were negligible. Meanwhile, TBQZY had extraordinary potential for combating drug-resistant bacteria in the clinical setting. This research not only provided new concepts for the design of AIEgens, but also shed some lights on the discovery of drugs against drug-resistant bacteria.

Zhao J., Han X.

AbstractA crucial step in life processes is the transfer of accurate and correct genetic material to offspring. During the construction of autonomous artificial cells, a very important step is the inheritance of genetic information in divided artificial cells. The ParMRC system, as one of the most representative systems for DNA segregation in bacteria, can be purified and reconstituted into GUVs to form artificial cells. In this study, we demonstrate that the eGFP gene is segregated into two poles by a ParM filament with ParR as the intermediate linker to bind ParM and parC-eGFP DNA in artificial cells. After the ParM filament splits, the cells are externally induced to divide into two daughter cells that contain parC-eGFP DNA by osmotic pressure and laser irradiation. Using a PURE system, we translate eGFP DNA into enhanced green fluorescent proteins in daughter cells, and bacterial plasmid segregation and inheritance are successfully mimicked in artificial cells. Our results could lead to the construction of more sophisticated artificial cells that can reproduce with genetic information.

Radler P., Loose M.

Bacteria divide by binary fission. The protein machine responsible for this process is the divisome, a transient assembly of more than 30 proteins in and on the surface of the cytoplasmic membrane. Together, they constrict the cell envelope and remodel the peptidoglycan layer to eventually split the cell into two. For Escherichia coli, most molecular players involved in this process have probably been identified, but obtaining the quantitative information needed for a mechanistic understanding can often not be obtained from experiments in vivo alone. Since the discovery of the Z-ring more than 30 years ago, in vitro reconstitution experiments have been crucial to shed light on molecular processes normally hidden in the complex environment of the living cell. In this review, we summarize how rebuilding the divisome from purified components – or at least parts of it - have been instrumental to obtain the detailed mechanistic understanding of the bacterial cell division machinery that we have today.

Delort A., Cottone G., Malliavin T.E., Müller M.M.

The toxicity of botulinum multi-domain neurotoxins (BoNTs) arises from a sequence of molecular events, in which the translocation of the catalytic domain through the membrane of a neurotransmitter vesicle plays a key role. A recent structural study of the translocation domain of BoNTs suggests that the interaction with the membrane is driven by the transition of an α helical switch towards a β hairpin. Atomistic simulations in conjunction with the mesoscopic Twister model are used to investigate the consequences of this proposition for the toxin–membrane interaction. The conformational mobilities of the domain, as well as the effect of the membrane, implicitly examined by comparing water and water–ethanol solvents, lead to the conclusion that the transition of the switch modifies the internal dynamics and the effect of membrane hydrophobicity on the whole protein. The central two α helices, helix 1 and helix 2, forming two coiled-coil motifs, are analyzed using the Twister model, in which the initial deformation of the membrane by the protein is caused by the presence of local torques arising from asymmetric positions of hydrophobic residues. Different torque distributions are observed depending on the switch conformations and permit an origin for the mechanism opening the membrane to be proposed.