scholarly journals Cell Diameter inBacillus subtilisis Determined by the Opposing Actions of Two Distinct Cell Wall Synthetic Systems

2018 ◽  
Author(s):  
Michael F. Dion ◽  
Mrinal Kapoor ◽  
Yingjie Sun ◽  
Sean Wilson ◽  
Joel Ryan ◽  
...  
Keyword(s):  
Cell Wall ◽  
Mechanical Anisotropy ◽  
Cell Diameter ◽  
Cell Width ◽  
Penicillin Binding Proteins ◽  
Distinct Cell ◽  
Rod System ◽  
Enzymatic Systems ◽  
Combined Action ◽  
Oriented Material

AbstractRod shaped bacteria grow by adding material into their cell wall via the action of two spatially distinct enzymatic systems: The Rod system moves around the cell circumference, while the class A penicillin-binding proteins (aPBPs) are unorganized. To understand how the combined action of these two systems defines bacterial dimensions, we examined how each system affects the growth and width ofBacillus subtilis, as well as the mechanical anisotropy and orientation of material within their sacculi. We find that rod diameter is not determined by MreB, rather it depends on the balance between the systems: The Rod system reduces diameter, while aPBPs increase it. RodA/PBP2A can both thin or widen cells, depending on its levels relative to MreBCD. Increased Rod system activity correlates with an increased density of directional MreB filaments, and a greater fraction of directionally moving PBP2A molecules. This increased circumferential synthesis increases the amount of oriented material within the sacculi, increasing their mechanical anisotropy and reinforcing rod shape. Together, these experiments explain how the combined action of the two main cell wall synthetic systems build rods of different widths, a model that appears generalizable:Escherichia colicontaining Rod system mutants show the same relationship between the density of directionally moving MreB filaments and cell width.

scholarly journals Bacillus subtilis cell diameter is determined by the opposing actions of two distinct cell wall synthetic systems

2019 ◽  
Vol 4 (8) ◽  
pp. 1294-1305 ◽  
Author(s):  
Michael F. Dion ◽  
Mrinal Kapoor ◽  
Yingjie Sun ◽  
Sean Wilson ◽  
Joel Ryan ◽  
...  
Keyword(s):  
Cell Wall ◽  
Bacillus Subtilis ◽  
Cell Diameter ◽  
Subtilis Cell ◽  
Distinct Cell

scholarly journals Neisseria gonorrhoeaePBP3 and PBP4 Facilitate NOD1 Agonist Peptidoglycan Fragment Release and Survival in Stationary Phase

2018 ◽  
Vol 87 (2) ◽  
Author(s):  
Ryan E. Schaub ◽  
Krizia M. Perez-Medina ◽  
Kathleen T. Hackett ◽  
Daniel L. Garcia ◽  
Joseph P. Dillard
Keyword(s):  
Molecular Weight ◽  
Cell Wall ◽  
Inflammatory Response ◽  
Neisseria Gonorrhoeae ◽  
Wild Type ◽  
Cross Link ◽  
Content Type ◽  
Lytic Transglycosylases ◽  
Penicillin Binding Proteins ◽  
Proinflammatory Molecules

ABSTRACTNeisseria gonorrhoeaereleases peptidoglycan fragments during growth, and these molecules induce an inflammatory response in the human host. The proinflammatory molecules include peptidoglycan monomers, peptidoglycan dimers, and free peptides. These molecules can be released by the actions of lytic transglycosylases or an amidase. However, >40% of the gonococcal cell wall is cross-linked, where the peptide stem on one peptidoglycan strand is linked to the peptide stem on a neighboring strand, suggesting that endopeptidases may be required for the release of many peptidoglycan fragments. Therefore, we characterized mutants with individual or combined mutations in genes for the low-molecular-mass penicillin-binding proteins PBP3 and PBP4. Mutations in eitherdacB, encoding PBP3, orpbpG, encoding PBP4, did not significantly reduce the release of peptidoglycan monomers or free peptides. A mutation indacBcaused the appearance of a larger-sized peptidoglycan monomer, the pentapeptide monomer, and an increased release of peptidoglycan dimers, suggesting the involvement of this enzyme in both the removal of C-terminald-Ala residues from stem peptides and the cleavage of cross-linked peptidoglycan. Mutation of bothdacBandpbpGeliminated the release of tripeptide-containing peptidoglycan fragments concomitantly with the appearance of pentapeptide and dipeptide peptidoglycan fragments and higher-molecular-weight peptidoglycan dimers. In accord with the loss of tripeptide peptidoglycan fragments, the level of human NOD1 activation by thedacB pbpGmutants was significantly lower than that by the wild type. We conclude that PBP3 and PBP4 overlap in function for cross-link cleavage and that these endopeptidases act in the normal release of peptidoglycan fragments during growth.

scholarly journals Escherichia coli Mutants Lacking All Possible Combinations of Eight Penicillin Binding Proteins: Viability, Characteristics, and Implications for Peptidoglycan Synthesis

1999 ◽  
Vol 181 (13) ◽  
pp. 3981-3993 ◽  
Author(s):  
Sylvia A. Denome ◽  
Pamela K. Elf ◽  
Thomas A. Henderson ◽  
David E. Nelson ◽  
Kevin D. Young
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Binding Proteins ◽  
Kanamycin Resistance ◽  
Open Reading Frames ◽  
Penicillin Binding Proteins ◽  
E Coli ◽  
Peptidoglycan Biosynthesis ◽  
Kanamycin Resistance Cassette ◽  
Genes Encoding

ABSTRACT The penicillin binding proteins (PBPs) synthesize and remodel peptidoglycan, the structural component of the bacterial cell wall. Much is known about the biochemistry of these proteins, but little is known about their biological roles. To better understand the contributions these proteins make to the physiology ofEscherichia coli, we constructed 192 mutants from which eight PBP genes were deleted in every possible combination. The genes encoding PBPs 1a, 1b, 4, 5, 6, and 7, AmpC, and AmpH were cloned, and from each gene an internal coding sequence was removed and replaced with a kanamycin resistance cassette flanked by two ressites from plasmid RP4. Deletion of individual genes was accomplished by transferring each interrupted gene onto the chromosome of E. coli via λ phage transduction and selecting for kanamycin-resistant recombinants. Afterwards, the kanamycin resistance cassette was removed from each mutant strain by supplying ParA resolvase in trans, yielding a strain in which a long segment of the original PBP gene was deleted and replaced by an 8-bpres site. These kanamycin-sensitive mutants were used as recipients in further rounds of replacement mutagenesis, resulting in a set of strains lacking from one to seven PBPs. In addition, thedacD gene was deleted from two septuple mutants, creating strains lacking eight genes. The only deletion combinations not produced were those lacking both PBPs 1a and 1b because such a combination is lethal. Surprisingly, all other deletion mutants were viable even though, at the extreme, 8 of the 12 known PBPs had been eliminated. Furthermore, when both PBPs 2 and 3 were inactivated by the β-lactams mecillinam and aztreonam, respectively, several mutants did not lyse but continued to grow as enlarged spheres, so that one mutant synthesized osmotically resistant peptidoglycan when only 2 of 12 PBPs (PBPs 1b and 1c) remained active. These results have important implications for current models of peptidoglycan biosynthesis, for understanding the evolution of the bacterial sacculus, and for interpreting results derived by mutating unknown open reading frames in genome projects. In addition, members of the set of PBP mutants will provide excellent starting points for answering fundamental questions about other aspects of cell wall metabolism.

scholarly journals FmhA and FmhC of Staphylococcus aureus incorporate serine residues into peptidoglycan cross-bridges

2020 ◽  
Vol 295 (39) ◽  
pp. 13664-13676 ◽  
Author(s):  
Stephanie Willing ◽  
Emma Dyer ◽  
Olaf Schneewind ◽  
Dominique Missiakas
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Wall ◽  
Binding Proteins ◽  
Penicillin Binding Proteins ◽  
Daughter Cells ◽  
Cross Bridge ◽  
Resistant Strains ◽  
The Cross ◽  
Cross Bridges ◽  
Adjacent Wall

Staphylococcal peptidoglycan is characterized by pentaglycine cross-bridges that are cross-linked between adjacent wall peptides by penicillin-binding proteins to confer robustness and flexibility. In Staphylococcus aureus, pentaglycine cross-bridges are synthesized by three proteins: FemX adds the first glycine, and the homodimers FemA and FemB sequentially add two Gly-Gly dipeptides. Occasionally, serine residues are also incorporated into the cross-bridges by enzymes that have heretofore not been identified. Here, we show that the FemA/FemB homologues FmhA and FmhC pair with FemA and FemB to incorporate Gly-Ser dipeptides into cross-bridges and to confer resistance to lysostaphin, a secreted bacteriocin that cleaves the pentaglycine cross-bridge. FmhA incorporates serine residues at positions 3 and 5 of the cross-bridge. In contrast, FmhC incorporates a single serine at position 5. Serine incorporation also lowers resistance toward oxacillin, an antibiotic that targets penicillin-binding proteins, in both methicillin-sensitive and methicillin-resistant strains of S. aureus. FmhC is encoded by a gene immediately adjacent to lytN, which specifies a hydrolase that cleaves the bond between the fifth glycine of cross-bridges and the alanine of the adjacent stem peptide. In this manner, LytN facilitates the separation of daughter cells. Cell wall damage induced upon lytN overexpression can be alleviated by overexpression of fmhC. Together, these observations suggest that FmhA and FmhC generate peptidoglycan cross-bridges with unique serine patterns that provide protection from endogenous murein hydrolases governing cell division and from bacteriocins produced by microbial competitors.

Development of Parametric Kelvin Structures will Closed Cells

2016 ◽  
Vol 254 ◽  
pp. 49-54 ◽  
Author(s):  
Dan Andrei Şerban ◽  
Emanoil Linul ◽  
Sorin Sărăndan ◽  
Liviu Marşavina
Keyword(s):  
Mechanical Properties ◽  
Cell Wall ◽  
Relative Density ◽  
Material Properties ◽  
Cell Diameter ◽  
Rigid Polyurethane Foam ◽  
Loading Direction ◽  
Convergence Study ◽  
Simulation Results ◽  
Mesh Convergence

This work presents the design of a parametric Kelvin structure in which the relative density of the geometry can be varied by adjusting three parameters: cell diameter, cell wall thickness and cell chamfer radius, the structure consistsing of a tessellation of hollow truncated octahedral. The developed model was evaluated in terms of compressive stiffness for the case of a rigid polyurethane foam of 0.256 relative density. Three models were analyzed in order to determine the influence of geometric characteristics on mechanical properties: a model that presented no chamfer a model that presented a medium-sized chamfer and a model that presented a large chamfer. A mesh convergence study was performed which analyzed the results in terms of accuracy and time expenses for three element sizes for both linear and quadratic elements. Due to the orthotropic nature of the model, its response on both possible loading directions was investigated. Simulation results were compared with experimental results and yielded accurate results for one loading direction, when using the material properties for solid polyurethane described in literature.

FREQUENCY OF MICRONUCLEI IN POLLEN QUARTETS OF COMMON WHEAT MONOSOMICS

1952 ◽  
Vol 30 (4) ◽  
pp. 371-378 ◽  
Author(s):  
J. W. Morrison ◽  
John Unrau
Keyword(s):  
Cell Wall ◽  
Common Wheat ◽  
Chinese Spring ◽  
Wheat Variety ◽  
Early Developmental Stage ◽  
D Genome ◽  
Distinct Cell ◽  
The Common ◽  
Early Developmental ◽  
Common Wheat Variety

The frequency with which 20 different monosomes of the common wheat variety, Chinese Spring, formed micronuclei in pollen quartets was determined. It was found that unless the study was made at an early developmental stage characterized by a distinct cell wall surrounding the quartets, the counts were unreliable, because some micronuclei were lost. The frequency of micronucleus formation was similar for anthers of a floret, florets of a spike, and plants of a monosome. Among the monosomes studied, there were three groups of three and four of two in which the total frequency of quartets with micronuclei, and the distribution of numbers of micronuclei per quartet, were strikingly similar. In the case of the groups of three, two monosomes were from the A and B genomes while one was from the D genome. This is interpreted as evidence of homoeology of chromosomes of a group and also that such chromosomes have undergone less change than those that do not form such series.

scholarly journals Glycome and Proteome Components of Golgi Membranes Are Common between Two Angiosperms with Distinct Cell-Wall Structures

2019 ◽  
Vol 31 (5) ◽  
pp. 1094-1112 ◽  
Author(s):  
Ikenna O. Okekeogbu ◽  
Sivakumar Pattathil ◽  
Susana M. González Fernández-Niño ◽  
Uma K. Aryal ◽  
Bryan W. Penning ◽  
...  
Keyword(s):  
Cell Wall ◽  
Golgi Membranes ◽  
Wall Structures ◽  
Distinct Cell
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