scholarly journals Dynamics of the Bacillus subtilis Min system

2020 ◽  
Author(s):  
Helge Feddersen ◽  
Laeschkir Würthner ◽  
Erwin Frey ◽  
Marc Bramkamp
Keyword(s):  
Bacillus Subtilis ◽  
Active Sites ◽  
Dynamic Equilibrium ◽  
Model Organism ◽  
Physical Modelling ◽  
Division Site ◽  
Diffusion Constants ◽  
Dynamic Equilibrium State ◽  
Min Proteins

SummaryDivision site selection is a vital process to ensure generation of viable offspring. In many rod-shaped bacteria a dynamic protein system, termed the Min system, acts as a central regulator of division site placement. The Min system is best studied in Escherichia coli where it shows a remarkable oscillation from pole to pole with a time-averaged density minimum at midcell. Several components of the Min system are conserved in the Gram-positive model organism Bacillus subtilis. However, in B. subtilis it is believed that the system forms a stationary bipolar gradient from the cell poles to midcell. Here, we show that the Min system of B. subtilis localizes dynamically to active sites of division, often organized in clusters. We provide physical modelling using measured diffusion constants that describe the observed enrichment of the Min system at the septum. Modelling suggests that the observed localization pattern of Min proteins corresponds to a dynamic equilibrium state. Our data provide evidence for the importance of ongoing septation for the Min dynamics, consistent with a major role of the Min system to control active division sites, but not cell pole areas.

scholarly journals SpoIIB Localizes to Active Sites of Septal Biogenesis and Spatially Regulates Septal Thinning during Engulfment in Bacillus subtilis

2000 ◽  
Vol 182 (4) ◽  
pp. 1096-1108 ◽  
Author(s):  
Ana R. Perez ◽  
Angelica Abanes-De Mello ◽  
Kit Pogliano
Keyword(s):  
Bacillus Subtilis ◽  
Fusion Protein ◽  
Mother Cell ◽  
Active Sites ◽  
Time Lapse ◽  
Formation Pathway ◽  
Time Lapse Microscopy ◽  
Division Site ◽  
Proposal A

ABSTRACT A key step in the Bacillus subtilis spore formation pathway is the engulfment of the forespore by the mother cell, a phagocytosis-like process normally accompanied by the loss of peptidoglycan within the sporulation septum. We have reinvestigated the role of SpoIIB in engulfment by using the fluorescent membrane stain FM 4-64 and deconvolution microscopy. We have found thatspoIIB mutant sporangia display a transient engulfment defect in which the forespore pushes through the septum and bulges into the mother cell, similar to the situation in spoIID,spoIIM, and spoIIP mutants. However, unlike the sporangia of those three mutants, spoIIB mutant sporangia are able to complete engulfment; indeed, by time-lapse microscopy, sporangia with prominent bulges were found to complete engulfment. Electron micrographs showed that in spoIIB mutant sporangia the dissolution of septal peptidoglycan is delayed and spatially unregulated and that the engulfing membranes migrate around the remaining septal peptidoglycan. These results demonstrate that mother cell membranes will move around septal peptidoglycan that has not been completely degraded and suggest that SpoIIB facilitates the rapid and spatially regulated dissolution of septal peptidoglycan. In keeping with this proposal, a SpoIIB-myc fusion protein localized to the sporulation septum during its biogenesis, discriminating between the site of active septal biogenesis and the unused potential division site within the same cell.

scholarly journals Dynamics of the Bacillus subtilis Min System

mBio ◽  
2021 ◽  
Vol 12 (2) ◽  
Author(s):  
Helge Feddersen ◽  
Laeschkir Würthner ◽  
Erwin Frey ◽  
Marc Bramkamp
Keyword(s):  
Bacillus Subtilis ◽  
Protein Dynamics ◽  
Site Selection ◽  
Active Sites ◽  
Molecular Mechanisms ◽  
Content Type ◽  
E Coli ◽  
Protein System ◽  
Division Site ◽  
Min Proteins

ABSTRACT Division site selection is a vital process to ensure generation of viable offspring. In many rod-shaped bacteria, a dynamic protein system, termed the Min system, acts as a central regulator of division site placement. The Min system is best studied in Escherichia coli, where it shows a remarkable oscillation from pole to pole with a time-averaged density minimum at midcell. Several components of the Min system are conserved in the Gram-positive model organism Bacillus subtilis. However, in B. subtilis, it is commonly believed that the system forms a stationary bipolar gradient from the cell poles to midcell. Here, we show that the Min system of B. subtilis localizes dynamically to active sites of division, often organized in clusters. We provide physical modeling using measured diffusion constants that describe the observed enrichment of the Min system at the septum. Mathematical modeling suggests that the observed localization pattern of Min proteins corresponds to a dynamic equilibrium state. Our data provide evidence for the importance of ongoing septation for the Min dynamics, consistent with a major role of the Min system in controlling active division sites but not cell pole areas. IMPORTANCE The molecular mechanisms that help to place the division septum in bacteria is of fundamental importance to ensure cell proliferation and maintenance of cell shape and size. The Min protein system, found in many rod-shaped bacteria, is thought to play a major role in division site selection. It was assumed that there are strong differences in the functioning and in the dynamics of the Min system in E. coli and B. subtilis. Most previous attempts to address Min protein dynamics in B. subtilis have been hampered by the use of overexpression constructs. Here, functional fusions to Min proteins have been constructed by allelic exchange and state-of-the-art imaging techniques allowed to unravel an unexpected fast dynamic behavior of the B. subtilis Min system. Our data show that the molecular mechanisms leading to Min protein dynamics are not fundamentally different in E. coli and B. subtilis.

scholarly journals Limiting the development of riparian vegetation in the Isère River: A physical modelling study

2018 ◽  
Vol 40 ◽  
pp. 02015
Author(s):  
Nicolas Claude ◽  
Clément Leroux ◽  
Marion Duclercq ◽  
Pablo Tassi ◽  
Kamal El Kadi Abderrezzak
Keyword(s):  
Plant Development ◽  
Dynamic Equilibrium ◽  
Initial Conditions ◽  
Physical Modelling ◽  
Sand Mixture ◽  
Dynamic Equilibrium State ◽  
Actual Configuration ◽  
Vegetation Encroachment ◽  
Movable Bed ◽  
Riparian Plant

Physical modelling experiments are conducted to investigate if a modification of the Isère River (French Alps) hydrology by changing dams management is able to foster riverbed morphodynamic and, thus limiting riparian plant development. The experimental setup is a 1:35 scale, undistorted movable bed designed to ensure the Froude number similarity and initial conditions for sediment particle motion. The physical model is 35 m long, 2.6 m wide, with a sand mixture composed of three grain size classes. Two runs with different flow and bed load conditions are simulated. Preliminary results show an intense riverbed activity when the system reaches a dynamic equilibrium state. Under these conditions, bar mobility is strong enough to limit vegetation encroachment only when water discharges are higher than the discharge of a 5-years flood during more than 10 days. These results indicate that the hydrological characteristics of the Isère River and the actual configuration of the hydropower structures could be not able to release annually the flow conditions needed to control riparian plant development.

scholarly journals Progression of the late-stage divisome is unaffected by the depletion of the cytoplasmic FtsZ pool

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Nadine Silber ◽  
Christian Mayer ◽  
Cruz L. Matos de Opitz ◽  
Peter Sass
Keyword(s):  
Bacillus Subtilis ◽  
Cell Division ◽  
Late Stage ◽  
Essential Role ◽  
Ftsz Ring ◽  
Division Site ◽  
Ring Dynamics ◽  
Cell Division Protein ◽  
Late Stages

AbstractCell division is a central and essential process in most bacteria, and also due to its complexity and highly coordinated nature, it has emerged as a promising new antibiotic target pathway in recent years. We have previously shown that ADEP antibiotics preferably induce the degradation of the major cell division protein FtsZ, thereby primarily leading to a depletion of the cytoplasmic FtsZ pool that is needed for treadmilling FtsZ rings. To further investigate the physiological consequences of ADEP treatment, we here studied the effect of ADEP on the different stages of the FtsZ ring in rod-shaped bacteria. Our data reveal the disintegration of early FtsZ rings during ADEP treatment in Bacillus subtilis, indicating an essential role of the cytoplasmic FtsZ pool and thus FtsZ ring dynamics during initiation and maturation of the divisome. However, progressed FtsZ rings finalized cytokinesis once the septal peptidoglycan synthase PBP2b, a late-stage cell division protein, colocalized at the division site, thus implying that the concentration of the cytoplasmic FtsZ pool and FtsZ ring dynamics are less critical during the late stages of divisome assembly and progression.

Role of the Structure and Electronic Properties of Fe2O3-MoO3 Catalyst on the Dehydration of Isopropyl Alcohol

1993 ◽  
Vol 58 (7) ◽  
pp. 1591-1599 ◽  
Author(s):  
Abd El-Aziz A. Said
Keyword(s):  
Active Sites ◽  
Isopropyl Alcohol ◽  
Oxide Catalyst ◽  
Flow System ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Catalyst Composition ◽  
Surface Active

Molybdenum oxide catalyst doped or mixed with (1 - 50) mole % Fe3+ ions were prepared. The structure of the original samples and the samples calcined at 400 °C were characterized using DTA, X-ray diffraction and IR spectra. Measurements of the electrical conductivity of calcined samples with and without isopropyl alcohol revealed that the conductance increases on increasing the content of Fe3+ ions up to 50 mole %. The activation energies of charge carriers were determined in presence and absence of the alcohol. The catalytic dehydration of isopropyl alcohol was carried out at 250 °C using a flow system. The results obtained showed that the doped or mixed catalysts are active and selective towards propene formation. However, the catalyst containing 40 mole % Fe3+ ions exhibited the highest activity and selectivity. Correlations were attempted to the catalyst composition with their electronic and catalytic properties. Probable mechanism for the dehydration process is proposed in terms of surface active sites.

Geometric Factor in Skeletal Reactions of 2-Methylpentane on Stepped Surfaces of Platinum Catalyst

1992 ◽  
Vol 57 (10) ◽  
pp. 2012-2020
Author(s):  
Vladimír Hejtmánek
Keyword(s):  
Active Sites ◽  
Platinum Catalyst ◽  
Point Of View ◽  
Geometric Factor ◽  
Published Data ◽  
Stepped Surfaces ◽  
Geometric Conditions ◽  
Surface Intermediates ◽  
Isomerization Mechanism

The role of geometric factor in the course of skeletal reactions (isomerization, hydrogenolysis) of 2-methylpentane on stepped (119), (557) and reconstructed R(557) surfaces of single crystals of platinum was evaluated with computer designed models. These calculations were compared with reported experimental data. It was found by analysis of geometric conditions that there are accessible active ensembles on double step of the reconstructed R(557) surface. In addition, these active sites are unsaturated in their coordination sphere and thus catalytically effective. This finding is consistent with published data, confirming higher catalytic activity of this surface. The various pathways of Bond Shift isomerization mechanism of 2-methylpentane from the point of view of steric demands of surface intermediates on differently located ensembles are discussed, too.

scholarly journals Cardiolipin-Containing Lipid Membranes Attract the Bacterial Cell Division Protein DivIVA

2021 ◽  
Vol 22 (15) ◽  
pp. 8350
Author(s):  
Naďa Labajová ◽  
Natalia Baranova ◽  
Miroslav Jurásek ◽  
Robert Vácha ◽  
Martin Loose ◽  
...  
Keyword(s):  
Cell Division ◽  
Lipid Bilayers ◽  
Bacterial Cell ◽  
Lipid Membranes ◽  
Model Organism ◽  
Active Role ◽  
Membrane Curvature ◽  
Bacterial Cell Division ◽  
Division Site ◽  
Clostridioides Difficile

DivIVA is a protein initially identified as a spatial regulator of cell division in the model organism Bacillus subtilis, but its homologues are present in many other Gram-positive bacteria, including Clostridia species. Besides its role as topological regulator of the Min system during bacterial cell division, DivIVA is involved in chromosome segregation during sporulation, genetic competence, and cell wall synthesis. DivIVA localizes to regions of high membrane curvature, such as the cell poles and cell division site, where it recruits distinct binding partners. Previously, it was suggested that negative curvature sensing is the main mechanism by which DivIVA binds to these specific regions. Here, we show that Clostridioides difficile DivIVA binds preferably to membranes containing negatively charged phospholipids, especially cardiolipin. Strikingly, we observed that upon binding, DivIVA modifies the lipid distribution and induces changes to lipid bilayers containing cardiolipin. Our observations indicate that DivIVA might play a more complex and so far unknown active role during the formation of the cell division septal membrane.

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