scholarly journals Fine Structure and Radiation Resistance in Acinetobacter: A Comparison Of A Range Of Strains

1971 ◽  
Vol 8 (1) ◽  
pp. 19-41
Author(s):  
AUDREY M. GLAUERT ◽  
MARGARET J. THORNLEY
Keyword(s):  
Cell Wall ◽  
Fine Structure ◽  
Outer Membrane ◽  
Radiation Resistance ◽  
Resistant Strain ◽  
The Other ◽  
Dense Layer ◽  
Gram Negative ◽  
Comparative Results ◽  
Resistance To Ionizing Radiation

Nine strains of the Gram-negative bacterium, Acinetobacter, showed a wide variation in resistance to ionizing radiation; all gave sigmoid survival curves, with D10 values for the exponential portion ranging from 70 to 460 J kg-1 (7-46 krd). The fine structure of these strains was studied by electron microscopy. Results for a resistant strain were described earlier and the present paper gives comparative results for the other 8 strains. The mode of division varied, 5 strains dividing predominantly by constriction of all the layers of the cell wall, while the other 4strains showed ingrowth of thick septa. These 4 included the 3 most resistant strains and I strain of intermediate resistance. The arrangement of surface layers was the same as that usually found in Gram-negative bacteria. In 1 strain an extra layer was visible outside the outer membrane; this layer does not appear to influence radiation resistance since it is lacking in another strain of similar resistance. The layer of wrinkled material, previously observed in the resistant strain between, the outer membrane and the intermediate dense layer of the cell wall, in negatively stained preparations of isolated cell walls, was seen in 5 other strains of intermediate and high resistance, while in 3 sensitive strains finely granular material appeared to occupy a corresponding position in the cell wall. These observations suggest that morphological features, such as the wrinkled layer of the cell wall, and possibly the mode of cell division, may influence the radiation resistance of Acinetobacter strains, but their function is not yet known.

Fine Structure and Radiation Resistance in Acinetobacter: Studies on a Resistant Strain

1968 ◽  
Vol 3 (2) ◽  
pp. 273-294
Author(s):  
MARGARET J. THORNLEY ◽  
AUDREY M. GLAUERT
Keyword(s):  
Cell Wall ◽  
Fine Structure ◽  
Radiation Resistance ◽  
Cell Walls ◽  
Proteolytic Enzymes ◽  
Gram Negative Bacteria ◽  
Intact Cells ◽  
Thin Sections ◽  
Gram Negative ◽  
Isolated Cell

An electron-microscope study of thin sections and negatively stained preparations of intact cells and isolated cell walls of a bacterium which is moderately resistant to ionizing radiation, Acinetobacter strain 199A, showed that it is similar to other Gram-negative bacteria except for its mode of division and for the fine structure of some of the surface layers. During division the cells form a fairly thick septum similar to those observed in Gram-positive bacteria. An examination of the appearance and chemical composition of isolated cell walls before and after treatment with enzymes, detergents and lipid solvents revealed that three layers, each with a characteristic fine structure, are present in the cell wall: (1) an outer membrane with an array of peg-like subunits; (2) a layer of wrinkled material which is digested by proteolytic enzymes; and (3) a smooth, rigid layer, which contains the mucopeptide components of the cell wall. These observations are compared with the results of other workers for various Gram-negative bacteria. From comparisons with the structure of more radiation-sensitive strains of Acinetobacter, it appears that layer (2) may be associated with the radiation resistance of the organism.

scholarly journals THE FINE STRUCTURE OF CHONDROCOCCUS COLUMNARIS

1967 ◽  
Vol 35 (1) ◽  
pp. 37-51 ◽  
Author(s):  
Jack L. Pate ◽  
Erling J. Ordal
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Fine Structure ◽  
Electron Microscope ◽  
Outer Membrane ◽  
Electron Microscope Study ◽  
Ruthenium Red ◽  
Gliding Motility ◽  
Dense Layer ◽  
Adhesive Properties

An electron microscope study of the myxobacterium Chondrococcus columnaris has revealed the following structures in the peripheral layers of the cells: (1) a plasma membrane, (2) a single dense layer (probably the mucopeptide component of the cell wall), (3) peripheral fibrils, (4) an outer membrane, and (5) a material coating the surfaces of the cells which could be stained with the dye ruthenium red.The ruthenium red-positive material is probably an acid mucopolysaccharide and may be involved in the adhesive properties of the cells. The outer membrane and plasma membrane both have the appearance of unit membranes: an electron-translucent layer sandwiched between two electron-opaque layers. The peripheral fibrils span the gap between the outer membrane and the mucopeptide layer, a distance of about 100 A, and run parallel to each other along the length of the cell. The fibrils appear to be continuous across the ends of the cells. The location of these fibrillar structures suggests that they may play a role in the gliding motility of these bacteria.

scholarly journals Endotoxins and the importance of procalcitonin

2019 ◽  
Vol 67 (1) ◽  
pp. 169-170
Author(s):  
Paola Andrea Yasnó-Navia ◽  
Luisa Fernanda Zuñiga-Ceron ◽  
Jhan Sebastián Saavedra-Torres ◽  
María Virginia Pinzón-Fernández
Keyword(s):  
Septic Shock ◽  
Immune Response ◽  
Cell Wall ◽  
Outer Membrane ◽  
Inflammatory Mediators ◽  
Platelet Activating Factor ◽  
Cellular Level ◽  
Lipid Mediators ◽  
The State ◽  
Gram Negative

Gram-negative bacilli and cocci bacteria produce and release endotoxins, which are lipopolysaccharides found in the outer membrane of the cell wall. These endotoxins are responsible for releasing a series of inflammatory mediators such as IL1, TNFα and proteases, as well as lipid mediators such as prostaglandins, leukotrienes, thromboxanes and platelet-activating factor, ultimately activitating immune response cells like leukocytes, macrophages and platelets. These cells amplify the response to shock, generate a procoagulant state and produce alterations at the cellular level, for example, damage to the endothelium, which in the end benefit and worsen the state of septic shock (Figure 1).

scholarly journals Mechanism of anchoring of OmpA protein to the cell wall peptidoglycan of the gram‐negative bacterial outer membrane

2011 ◽  
Vol 26 (1) ◽  
pp. 219-228 ◽  
Author(s):  
Jeong Soon Park ◽  
Woo Cheol Lee ◽  
Kwon Joo Yeo ◽  
Kyoung‐Seok Ryu ◽  
Malika Kumarasiri ◽  
...  
Keyword(s):  
Cell Wall ◽  
Outer Membrane ◽  
Gram Negative ◽  
Cell Wall Peptidoglycan ◽  
Ompa Protein ◽  
Bacterial Outer Membrane

Infectious disease

2019 ◽  
Author(s):  
Stevan R. Emmett ◽  
Nicola Hill ◽  
Federico Dajas-Bailador
Keyword(s):  
Cell Wall ◽  
Protein Synthesis ◽  
Nucleic Acid ◽  
Outer Membrane ◽  
Bacterial Cell ◽  
Bacterial Cell Wall ◽  
Gram Negative Bacteria ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Positive Bacteria

Antibiotics include an extensive range of agents able to kill or prevent reproduction of bacteria in the body, without being overly toxic to the patient. Traditionally derived from living organisms, most are now chemically synthesized and act to disrupt the integrity of the bacterial cell wall, or penetrate the cell and disrupt protein synthesis or nucleic acid replication. Typically, bacteria are identified according to their ap­pearance under the microscope depending on shape and response to the Gram stain test. Further identification is obtained by growth characteristics on various types of culture media, based on broth or agar, biochemical and immunological profiles. Further testing on broth or agar determines antibiotic sensitivity to guide on anti­biotic therapy in individual patients. This process can take 24– 48 hours to culture and a further 24– 48 hours to measure sensitivities. Increasingly, new technology, e.g. Matrix Assisted Laser Desorption Ionization— Time of Flight (MALDI- TOF) and nucleic acid amplification as­says, are being used to provide more rapid identification. The Gram classification, however, is still widely referred to as it differentiates bacteria by the presence or absence of the outer lipid membrane (see Figure 11.1), a fundamental characteristic that influences antibiotic management. Antimicrobial agents rely on selective action exploiting genetic differences between bacterial and eukaryotic cells. They target bacterial cell wall synthesis, bacterial protein synthesis, microbial DNA or RNA synthesis, by acting on bacterial cell metabolic pathways or by inhibiting the ac­tion of a bacterial toxin (see Table 11.1). Both Gram- positive and Gram- negative bacteria possess a rigid cell wall able to protect the bacteria from varying osmotic pressures (Figure 11.1). Peptidoglycan gives the cell wall its rigidity and is composed of a glycan chain of complex alternating carbohydrates, N- acetylglucosamide (N- ATG), and N- acetylmurcarinic acid (N- ATM), that are cross- linked by peptide (or glycine) chains. In Gram-positive bacteria, the cell wall contains multiple peptido­glycan layers, interspersed with teichoic acids, whereas Gram- negative bacteria contain only one or two peptido­glycan layers that are surrounded by an outer membrane attached by lipoproteins. The outer membrane contains porins (which regulate transport of substances into and out of the cell), lipopolysaccharides, and outer proteins in a phospholipid bilayer. For both Gram- negative and Gram-positive bacteria, peptidoglycan synthesis involves about 30 bacterial enzymes acting over three stages. Since the cell wall is unique to bacteria, it makes a suitable target for antibiotic therapy.

The surface anatomy of Lampropedia hyalina

1963 ◽  
Vol 158 (973) ◽  
pp. 498-513 ◽  
Keyword(s):  
Cell Wall ◽  
Fine Structure ◽  
The Other ◽  
Hexagonal Array ◽  
Outer Envelope ◽  
Surface Anatomy ◽  
Continuous Sheet ◽  
Electron Microscopical ◽  
Amorphous Zone ◽  
Honeycomb Network

The fine structure of the superficial layers of the tablet-forming micro-organism, Lampropedia hyalina , has been studied by several electron microscopical techniques. The outer envelope is distinct from the cell wall and surrounds not individual cells but groups of cells (tablets). This envelope appears to embody two complex layers, both possessing a regular-patterned structure. One layer (the perforate layer) is a honeycomb network of hexagonally distributed holes, each about 75 Å in diameter, and with a repeat spacing, from centre to centre, of 145 Å. The other, outermost (punctate) layer, which seems to be fragile and easily lost, is composed of outward-projecting spines, also in hexagonal array but with a repeat spacing of 260 Å. The probable structural relationship between the perforate and punctate layers is discussed. The structured envelope is separated from the cells by an amorphous zone (the intercalated zone) about 600 Å thick; this penetrates between the cells of a tablet and follows immediately behind the ingrowing septum in cell division. The intercalated zone is probably the important factor in cell cohesion; the significance of the structured envelope is uncertain but its function may be to separate the sheet into tablets by preventing intercell cohesion at certain places in what would otherwise be a continuous sheet of cells.

scholarly journals Outer membrane permeabilization by the membrane attack complex sensitizes Gram-negative bacteria to antimicrobial proteins in serum and phagocytes

2021 ◽  
Vol 17 (1) ◽  
pp. e1009227
Author(s):  
Dani A. C. Heesterbeek ◽  
Remy M. Muts ◽  
Vincent P. van Hensbergen ◽  
Pieter de Saint Aulaire ◽  
Tom Wennekes ◽  
...  
Keyword(s):  
Cell Wall ◽  
Immune System ◽  
Outer Membrane ◽  
Bacterial Cell ◽  
Cell Envelope ◽  
Membrane Attack Complex ◽  
Human Neutrophils ◽  
Gram Negative Bacteria ◽  
Antimicrobial Proteins ◽  
Gram Negative

Infections with Gram-negative bacteria form an increasing risk for human health due to antibiotic resistance. Our immune system contains various antimicrobial proteins that can degrade the bacterial cell envelope. However, many of these proteins do not function on Gram-negative bacteria, because the impermeable outer membrane of these bacteria prevents such components from reaching their targets. Here we show that complement-dependent formation of Membrane Attack Complex (MAC) pores permeabilizes this barrier, allowing antimicrobial proteins to cross the outer membrane and exert their antimicrobial function. Specifically, we demonstrate that MAC-dependent outer membrane damage enables human lysozyme to degrade the cell wall of E. coli. Using flow cytometry and confocal microscopy, we show that the combination of MAC pores and lysozyme triggers effective E. coli cell wall degradation in human serum, thereby altering the bacterial cell morphology from rod-shaped to spherical. Completely assembled MAC pores are required to sensitize E. coli to the antimicrobial actions of lysozyme and other immune factors, such as Human Group IIA-secreted Phospholipase A2. Next to these effects in a serum environment, we observed that the MAC also sensitizes E. coli to more efficient degradation and killing inside human neutrophils. Altogether, this study serves as a proof of principle on how different players of the human immune system can work together to degrade the complex cell envelope of Gram-negative bacteria. This knowledge may facilitate the development of new antimicrobials that could stimulate or work synergistically with the immune system.

scholarly journals THE FINE STRUCTURE OF STALKED BACTERIA BELONGING TO THE FAMILY CAULOBACTERACEAE

1964 ◽  
Vol 23 (3) ◽  
pp. 587-607 ◽  
Author(s):  
Jeanne L. Stove Poindexter ◽  
Germaine Cohen-Bazire
Keyword(s):  
Cell Wall ◽  
Fine Structure ◽  
Cell Membrane ◽  
Multilayered Structure ◽  
Gram Negative Bacteria ◽  
Thin Sections ◽  
Gram Negative ◽  
Cytoplasmic Region ◽  
The Core ◽  
The Family

The fine structure of a series of stalked bacteria belonging to the genera Caulobacter and Asticcacaulis has been examined in thin sections. The cell wall has the multilayered structure typical of many Gram-negative bacteria, and continues without interruption throughout the length of the stalk. The core of the stalk, continuous with the cytoplasmic region of the cell, is enclosed in an extension of the cell membrane, and contains a system of internal membranes: it is devoid of ribosomes and nucleoplasm. A membranous organelle occupies the juncture of stalk and cell, separating the ribosomal region from the core of the stalk. Typical mesosomes also occur in the cell, being particularly frequent at the plane of division. The secreted holdfast is located at the tip of the stalk in Caulobacter, and at the pole of the cell adjacent to the stalk in Asticcacaulis.

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