Radioautographic Evidence for Equatorial Wall Growth in a Gram-Positive Bacterium

Briles, Eve Barak; Tomasz, Alexander

doi:10.1083/jcb.47.3.786

Cited by 68 publications

(45 citation statements)

References 9 publications

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“…The localized staining may indicate either a loss of surface-expressed PspA over time or the fact that proteins like PspA and PspC may be secreted to the surface in a localized manner. It is interesting that production of the cell wall of pneumococci was limited to a thin growing zone in the lateral body of the bacterial cell (18). Whether PspA and PspC are secreted in conjunction with the production of cell wall remains to be determined.…”

Section: Discussionmentioning

confidence: 99%

Characterization of Binding of Human Lactoferrin to Pneumococcal Surface Protein A

et al. 2001

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Human lactoferrin is an iron-binding glycoprotein that is particularly prominent in exocrine secretions and leukocytes and is also found in serum, especially during inflammation. It is able to sequester iron from microbes and has immunomodulatory functions, including inhibition of both complement activation and cytokine production. This study used mutants lacking pneumococcal surface protein A (PspA) and PspC to demonstrate that the binding of human lactoferrin to the surface of Streptococcus pneumoniae was entirely dependent on PspA. Lactoferrin bound both family 1 and family 2 PspAs. Binding of lactoferrin to PspA was shown by surface colocalization with PspA and was verified by the lack of binding to PspA-negative mutants. Lactoferrin was expressed on the body of the cells but was largely absent from the poles. PspC showed exactly the same distribution on the pneumococcal surface as PspA but did not bind lactoferrin. PspA's binding site for lactoferrin was mapped using recombinant fragments of PspA of families 1 and 2. Binding of human lactoferrin was detected primarily in the C-terminal half of the ␣-helical domain of PspA (amino acids 167 to 288 of PspA/Rx1), with no binding to the N-terminal 115 amino acids in either strain. The interaction was highly specific. As observed previously, bovine lactoferrin bound poorly to PspA. Human transferrin did not bind PspA at all. The binding of lactoferrin to S. pneumoniae might provide a way for the bacteria to interfere with host immune functions or to aid in the acquisition of iron at the site of infection.Lactoferrin is an iron-binding glycoprotein present in milk and mucosal secretions. It is also released by specific granules of polymorphonuclear leukocytes during inflammation (35,36). It is a member of the siderophilin family and is structurally related to the more abundant serum protein transferrin (40). Lactoferrin has been ascribed many diverse biological functions, most of which are immunomodulatory or antibacterial (5, 7, 20-22, 37, 57, 58). It can inhibit cytokine activation, myelopoiesis, and complement activation (21,34,37,54). It also plays a role in host resistance by sequestering from bacteria the free iron necessary for bacterial growth and by the bactericidal activity of an N-terminal fragment released after pepsin digestion in the gut (22,56,58).Streptococcus pneumoniae is an important cause of respiratory tract infections, bacteremia, and meningitis. These infections are especially common in young children and in the elderly (3, 26). Infection usually starts with asymptomatic carriage in the nasopharynx. Bacteria can then, in some cases, spread to other locations such as the lungs, middle ear, and blood (4, 26, 55). To effectively infect the host, pneumococci have to survive and evade the immune system in the nasopharynx as well as at other sites within the host. This may be accomplished by binding immunomodulatory molecules, such as lactoferrin, at the site of infection. S. pneumoniae has been reported to bind lactoferrin (28).Using radiolabeled...

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Section: Discussionmentioning

confidence: 99%

Characterization of Binding of Human Lactoferrin to Pneumococcal Surface Protein A

et al. 2001

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“…S. pneumoniae and S. gordonii are ovoid (43). The equatorial ring is identified by an increased curvature of the plasma membrane and is approximately halfway between the septum and the cell pole (6,43). The GL, IWZ, and OWZ are not different at the equatorial ring (Fig.…”

Section: Aspect Of Vitreous Sections a Typical Section Of S Gordonimentioning

confidence: 99%

Granular Layer in the Periplasmic Space of Gram-Positive Bacteria and Fine Structures ofEnterococcus gallinarumandStreptococcus gordoniiSepta Revealed by Cryo-Electron Microscopy of Vitreous Sections

Zuber

Haenni

Ribeiro³

et al. 2006

J Bacteriol

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High-resolution structural information on optimally preserved bacterial cells can be obtained with cryoelectron microscopy of vitreous sections. With the help of this technique, the existence of a periplasmic space between the plasma membrane and the thick peptidoglycan layer of the gram-positive bacteria Bacillus subtilis and Staphylococcus aureus was recently shown. This raises questions about the mode of polymerization of peptidoglycan. In the present study, we report the structure of the cell envelope of three gram-positive bacteria (B. subtilis, Streptococcus gordonii, and Enterococcus gallinarum). In the three cases, a previously undescribed granular layer adjacent to the plasma membrane is found in the periplasmic space. In order to better understand how nascent peptidoglycan is incorporated into the mature peptidoglycan, we investigated cellular regions known to represent the sites of cell wall production. Each of these sites possesses a specific structure. We propose a hypothetic model of peptidoglycan polymerization that accommodates these differences: peptidoglycan precursors could be exported from the cytoplasm to the periplasmic space, where they could diffuse until they would interact with the interface between the granular layer and the thick peptidoglycan layer. They could then polymerize with mature peptidoglycan. We report cytoplasmic structures at the E. gallinarum septum that could be interpreted as cytoskeletal elements driving cell division (FtsZ ring). Although immunoelectron microscopy and fluorescence microscopy studies have demonstrated the septal and cytoplasmic localization of FtsZ, direct visualization of in situ FtsZ filaments has not been obtained in any electron microscopy study of fixed and dehydrated bacteria.Gram-positive bacteria possess a cell envelope composed of a plasma membrane and a thick network of peptidoglycan, secondary acids, and proteins, which maintains cell shape and provides resistance to osmotic pressure (39). Electron microscopy studies performed on fixed (either chemically or by freezing) and dehydrated specimens favored the widely accepted model of the cell envelope consisting of the peptidoglycan network in direct contact with the plasma membrane (4). Nevertheless, the existence of a periplasmic space separated from the cytoplasm and the outer medium by a plasma membrane and a thick cell wall has been suggested by previous biochemical studies (3,14,25). Recent data obtained with cryo-electron microscopy of vitreous sections (CEMOVIS), a method that allows the observation of biological specimens in the closest-to-native state, challenged the classical model (23,24). CEMOVIS consists of cooling the specimen at high pressure so rapidly that water cannot crystallize and instead becomes vitreous. Water stays liquid, but its viscosity dramatically increases (10). It is then possible to make thin sections at low temperatures and observe them using a cryo-electron microscope (1). Consequently, water does not need to be removed from the sample, and molecular aggrega...

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“…By following the segregation of [ 3 H]choline-labeled teichoic acid in the cell wall, evidence for equatorial cell wall growth was found in S. pneumoniae (18). In a different study, Tomasz and colleagues took advantage of the fact that choline-containing cell wall is sensitive to autolysin whereas ethanolamine-containing cell wall is not.…”

Section: Pbp2xmentioning

confidence: 99%

Bacterial Cell Wall Synthesis: New Insights from Localization Studies

Scheffers

Pinho

2005

Microbiol Mol Biol Rev

539

489

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SUMMARY In order to maintain shape and withstand intracellular pressure, most bacteria are surrounded by a cell wall that consists mainly of the cross-linked polymer peptidoglycan (PG). The importance of PG for the maintenance of bacterial cell shape is underscored by the fact that, for various bacteria, several mutations affecting PG synthesis are associated with cell shape defects. In recent years, the application of fluorescence microscopy to the field of PG synthesis has led to an enormous increase in data on the relationship between cell wall synthesis and bacterial cell shape. First, a novel staining method enabled the visualization of PG precursor incorporation in live cells. Second, penicillin-binding proteins (PBPs), which mediate the final stages of PG synthesis, have been localized in various model organisms by means of immunofluorescence microscopy or green fluorescent protein fusions. In this review, we integrate the knowledge on the last stages of PG synthesis obtained in previous studies with the new data available on localization of PG synthesis and PBPs, in both rod-shaped and coccoid cells. We discuss a model in which, at least for a subset of PBPs, the presence of substrate is a major factor in determining PBP localization.

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Radioautographic Evidence for Equatorial Wall Growth in a Gram-Positive Bacterium

Cited by 68 publications

References 9 publications

Characterization of Binding of Human Lactoferrin to Pneumococcal Surface Protein A

Characterization of Binding of Human Lactoferrin to Pneumococcal Surface Protein A

Granular Layer in the Periplasmic Space of Gram-Positive Bacteria and Fine Structures ofEnterococcus gallinarumandStreptococcus gordoniiSepta Revealed by Cryo-Electron Microscopy of Vitreous Sections

Bacterial Cell Wall Synthesis: New Insights from Localization Studies

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