Bacterial physiology: Life minus Z

Boer, Piet A. J. de

doi:10.1038/nmicrobiol.2016.121

Cited by 3 publications

(5 citation statements)

References 15 publications

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“…A straightforward model for giant cell formation is that after inhibition of peptidoglycan synthesis blocks cell enlargement, the activity of hydrolytic functions ruptures the peptidoglycan sheath, allowing the growing cytoplasm to break out of it and expand [5, 13]. To identify functions potentially involved in this process, we screened for mutations altering giant cell recovery using saturation-level transposon mutant sequencing (Tn-seq).…”

Section: Resultsmentioning

confidence: 99%

“…These bacteria have been an object of fascination for decades due to their capacity for growth without a peptidoglycan sheath, striking cell morphologies and antibiotic resistance [14, 15]. It appears that the formation of L-forms requires not only loss of peptidoglycan synthesis, but also additional mutations that allow the wall-deficient forms to proliferate by membrane tubulation and blebbing [5].…”

Section: Introductionmentioning

confidence: 99%

“…In some cases, loss of peptidoglycan synthesis leads not to L-forms, but to non-proliferating cells that have lost their normal shape and may enlarge considerably [5, 12, 13, 16–19]. For example, in one well-characterized example, mutations inactivating an E .…”

Section: Introductionmentioning

confidence: 99%

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Essential gene deletions producing gigantic bacteria

et al. 2019

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To characterize the consequences of eliminating essential functions needed for peptidoglycan synthesis, we generated deletion mutations of Acinetobacter baylyi by natural transformation and visualized the resulting microcolonies of dead cells. We found that loss of genes required for peptidoglycan precursor synthesis or polymerization led to the formation of polymorphic giant cells with diameters that could exceed ten times normal. Treatment with antibiotics targeting early or late steps of peptidoglycan synthesis also produced giant cells. The giant cells eventually lysed, although they were partially stabilized by osmotic protection. Genome-scale transposon mutant screening (Tn-seq) identified mutations that blocked or accelerated giant cell formation. Among the mutations that blocked the process were those inactivating a function predicted to cleave murein glycan chains (the MltD murein lytic transglycosylase), suggesting that giant cell formation requires MltD hydrolysis of existing peptidoglycan. Among the mutations that accelerated giant cell formation after ß-lactam treatment were those inactivating an enzyme that produces unusual 3->3 peptide cross-links in peptidoglycan (the LdtG L,D-transpeptidase). The mutations may weaken the sacculus and make it more vulnerable to further disruption. Although the study focused on A . baylyi , we found that a pathogenic relative ( A . baumannii ) also produced giant cells with genetic dependencies overlapping those of A . baylyi . Overall, the analysis defines a genetic pathway for giant cell formation conserved in Acinetobacter species in which independent initiating branches converge to create the unusual cells.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Essential gene deletions producing gigantic bacteria

et al. 2019

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“…An N-terminal portion of DedD ( N DedD) is required and sufficient for its function in cell division. DedD consists of a small cytoplasmic domain (DedD [1][2][3][4][5][6][7][8] ), a transmembrane domain (DedD 9 -27 , or TM DedD), and a large periplasmic domain (DedD 28 -220 ) (71,84). The last contains a C-terminal globular SPOR domain (DedD 140 -216 , or S DedD), and secondary structure predictions (85,86) suggest that the remainder (DedD 28 -139 ) lacks a defined structure save for five possible short ␣-helices, H1 to H5 (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The tubulin-like GTPase FtsZ forms linear homopolymers (Z polymers) and plays a key role in cytokinesis of most prokaryotes and many plastids (2)(3)(4). SR assembly starts with the coaccumulation of Z polymers and several core (FtsA and ZipA) and noncore (ZapA, -C, and -D) FtsZ-binding proteins in a ring-like arrangement on the inner face of the IM at the prospective site of fission.…”

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confidence: 99%

Roles of the DedD Protein in Escherichia coli Cell Constriction

et al. 2019

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Two key tasks of the bacterial septal-ring (SR) machinery during cell constriction are the generation of an inward-growing annulus of septal peptidoglycan (sPG) and the concomitant splitting of its outer edge into two layers of polar PG that will be inherited by the two new cell ends. FtsN is an essential SR protein that helps trigger the active constriction phase in Escherichia coli by inducing a self-enhancing cycle of processes that includes both sPG synthesis and splitting and that we refer to as the sPG loop. DedD is an SR protein that resembles FtsN in several ways. Both are bitopic inner membrane proteins with small N-terminal cytoplasmic parts and larger periplasmic parts that terminate with a SPOR domain. Though absence of DedD normally causes a mild cell-chaining phenotype, the protein is essential for division and survival of cells with limited FtsN activity. Here, we find that a small N-terminal portion of DedD (NDedD; DedD1–54) is required and sufficient to suppress ΔdedD-associated division phenotypes, and we identify residues within its transmembrane domain that are particularly critical to DedD function. Further analyses indicate that DedD and FtsN act in parallel to promote sPG synthesis, possibly by engaging different parts of the FtsBLQ subcomplex to induce a conformation that permits and/or stimulates the activity of sPG synthase complexes composed of FtsW, FtsI (PBP3), and associated proteins. We propose that, like FtsN, DedD promotes cell fission by stimulating sPG synthesis, as well as by providing positive feedback to the sPG loop. IMPORTANCE Cell division (cytokinesis) is a fundamental biological process that is incompletely understood for any organism. Division of bacterial cells relies on a ring-like machinery called the septal ring or divisome that assembles along the circumference of the mother cell at the site where constriction eventually occurs. In the well-studied bacterium Escherichia coli, this machinery contains over 30 distinct proteins. We identify functionally important parts of one of these proteins, DedD, and present evidence supporting a role for DedD in helping to induce and/or sustain a self-enhancing cycle of processes that are executed by fellow septal-ring proteins and that drive the active constriction phase of the cell division cycle.

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Bacterial Cell Division

Natale

Vicente

2020

Encyclopedia of Life Sciences

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Escherichia coli assembles a contractile ring, the divisome, in its envelope at the middle of its length exactly when it is needed for division. Its main component, FtsZ, is a cytoplasmic protein lacking the ability to be positioned by itself in the membrane. Additional proteins regulate either the action, the positioning or the stability of FtsZ by interacting with a unique region called the FtsZ ‘central hub’. The assembly of the divisome is initiated by a proto‐ring, in which ZipA and FtsA are two proteins that use the central hub for attaching FtsZ to the membrane. Polymerisation of FtsZ is blocked at the poles by the MinCDE proteins and also prevented by SlmA to occur at places adjacent to the nucleoid. After nucleoid segregation, the divisome becomes functional at midcell where it triggers invagination of the membrane and the production of septal peptidoglycan, leading ultimately to an efficient cell division. Key Concepts Division depends on a cytoskeletal element (FtsZ ring) that functions as a scaffold to recruit additional division proteins. Spatial regulation of the FtsZ‐ring placement involves positioning inhibitors of FtsZ in the cell to prevent FtsZ polymers from assembling at the poles or across unsegregated nucleoids. Several complexes that effect the division process localise at specific places of the cell at precise moments after growth and nucleoid segregation. The interactions of FtsZ, a cytoplasmic protein, with the proto‐ring anchors, FtsA and ZipA, serve to associate it to the cytoplasmic membrane forming the proto‐ring, the initial precursor of the division machinery. The central hub of FtsZ is key to the action of the FtsZ regulatory proteins FtsA, FtsE, FtsX, ZipA, ZapC, ZapD, MinC, SlmA and ClpX. The Min proteins generate an oscillatory pattern in artificial systems, and FtsZ filaments can form rings when attached to a lipid bilayer that has a cylindrical shape. PBP3‐independent peptidoglycan synthesis (PIPS) prior to the production of septal peptidoglycan directly connects cytoplasmic division proteins with peptidoglycan synthesis in the bacterial periplasm.

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Bacterial physiology: Life minus Z

Cited by 3 publications

References 15 publications

Essential gene deletions producing gigantic bacteria

Essential gene deletions producing gigantic bacteria

Roles of the DedD Protein in Escherichia coli Cell Constriction

Bacterial Cell Division

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