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Characterization of Microorganisms by Pyrolysis-GC, Pyrolysis-GC/MS, and Pyrolysis-MS
Published in Karen D. Sam, Thomas P. Wampler, Analytical Pyrolysis Handbook, 2021
Stephen L. Morgan, Bruce E. Watt, Randolph C. Galipo
The cell envelope usually consists of a cell membrane, a cell wall, and an outer membrane [21,22]. Figure 9.1 shows schematic representations of the structure of Gram-positive and Gram-negative cell envelopes. The cell wall consists of the peptidoglycan (PG) layer and associated structures. PG is the only substance common to almost all bacteria (except Mycoplasma and Chlamydia) and absent in non-bacterial matter [23]. PG and its associated chemical components may account for up to 10–40% of the dry weight of the cell [5]. As seen in Figure 9.2, PG consists of a polysaccharide backbone that is a repeating polymer of N-acetylglucosamine and N-acetylmuramic acid. Attached covalently to the lactyl group of muramic acid are tetra- and pentapeptides (composed of repeating l- and d-amino acids) cross-linked by peptide bridges. The amino sugar muramic acid (3-O--carboxethyl-D-glucosamine) is a fairly definitive marker for bacteria. Other chemical markers in PG include d-alanine, d-glutamic acid, and diaminopimelic acid [24,25]. The d-amino acids are sometimes found in other bacterial components but are not synthesized by mammals. Different bacteria may vary in the sequence of the amino acids in the peptide sidechains and crossbridge.
Chapter 10: The Use of Microspheres in the Study of cell Motility
Published in Alan Rembaum, Zoltán A. Tökés, Micro spheres: Medical and Biological Applications, 2017
Pate and Chang21 observed the movements of polystyrene microspheres (0.76 μm diameter) along the surface of gliding cells of Cytophaga johnsonae and Flexibacter columnaris. Cytophaga possesses a typical Gram-negative cell envelope consisting of a cytoplasmic membrane, a peptidoglycan layer, and an outer membrane composed of lipopolysaccharide and protein. Flexibacter has a similar structure but, in addition, certain species (F. poly- morphus) possess unusual surface features that resemble goblets;22 the presence of these surface specializations does not directly correlate with the presence of gliding motility. Pate and Chang21 reported a variety of microsphere movements: (1) they could move up one side of the elongated cell, around the end and down the other side; (2) they could stop and reverse direction; and (3) they could remain at one end of the cell while rotating in position. Movements of different microspheres on the same cell were independent of one another. All environmental conditions or inhibitors (such as cyanide and a variety of proton conductors) that stopped gliding motility also stopped microsphere motility. Nongliding mutants failed to exhibit microsphere movement. These same authors observed ring-shape structures in the wall of Cytophaga and hypothesized that these structures are analogous to the ring structure of the basal bodies associated with bacterial flagella; they argued that rotation of these structures may be the mechanism for gliding motility and microsphere movements.
Complement Activation: Challenges to Nanomedicine Development
Published in Raj Bawa, János Szebeni, Thomas J. Webster, Gerald F. Audette, Immune Aspects of Biopharmaceuticals and Nanomedicines, 2019
Dennis E. Hourcade, Christine T. N. Pham, Gregory M. Lanza
The cell envelope of Gram-negative bacteria contains two membranes, an inner cytoplasmic membrane and an outer membrane. Between them resides the peptidoglycan in a region known as the periplasm. The outer membrane contains a layer of lipopolysaccharides, or LPS, which extends into the cell exterior. The effect of C on Gram-negative bacteria is modulated by variations in these outer structures. Most Gram-negative bacteria can engage the CP and/or the AP and are subject to clearance by the MPS, but some, like N. meningitidis, the agent of meningococcal disease, are particularly vulnerable to the MAC. Those deficient in C alternative and terminal pathway components are highly prone to repeated infection by N. meningitidis [12].
Formation of planar hybrid lipid/polymer membranes anchored to an S-layer protein lattice by vesicle binding and rupture
Published in Soft Materials, 2020
Christian Czernohlavek, Bernhard Schuster
There are significant efforts to design synthetic membranes as mimics of biomembranes.[1] The building blocks of bio-inspired systems constitute unique, predictable and tunable properties, diversity, and the possibility to fabricate ultrathin two-dimensional structures in the square-micrometer range with an astonishing variety of functionalities at the nanoscale.[2–7] Moreover, these natural building blocks like, e.g., lipids, proteins, and polymers self-assemble spontaneously into supramolecular structures.[8–10] One of the most important template for bio-inspired architectures is the cell envelope structure of prokaryotes, which is a complex layered structure comprising of a cell membrane and in many cases of a monomolecular array of protein subunits forming the outermost surface layer (S-layer).[4,9,11,12] The importance of cell membranes in biological systems as a barrier, preserver of the physical integrity of the cell and host for integral membrane proteins has prompted the development of membrane platforms that recapitulate fundamental aspects of membrane biology, especially the lipid bilayer environment.[7,13,14] This environment is of utmost importance for integral membrane proteins like channels, proton pumps, and (G protein-coupled) receptors, which are responsible for carrying out important specific membrane functions.[15–19]
Cr–Ag coatings: synthesis, microstructure and antimicrobial properties
Published in Surface Engineering, 2019
Afshin Karami, Hu Zhang, Victoria G. Pederick, Christopher A. McDevitt, Mohammad Sharear Kabir, Song Xu, Paul Munroe, Zhifeng Zhou, Zonghan Xie
According to the Japanese standard JIS Z 2801:2010 [41], the treatment time for the bacteria on the sample surfaces is 24 ± 1 h. However, examination of bacterial survival after 24 h on Cr–Ag coatings using either 4.83% or 15.23% Ag resulted in 100% killing against both tested bacteria (data not presented). Rather, in the present study, the treatment time was set to be 1 h to enable comparison of the antibacterial efficacy for different Cr–Ag coatings. Also, within a hospital setting, it is likely that a time-frame for the bacterial killing of more than 1 h would be beneficial for reducing bacterial transmission from contaminated surfaces. Our analyses demonstrated bacterial survival had an order of 15.23% Ag > 4.83% Ag > 100% Ag. While this was consistent across both the Gram-negative bacterium E. coli and the Gram-positive bacterium S. aureus, the level of survival for S. aureus on the surfaces was greater than that for E. coli. This may indicate that the differences in the cell envelope structure play a role in resistance to killing on the tested surfaces. Gram-positive bacteria featuring a single membrane and a thicker protective peptidogylcan cell wall, and this is in contrast to the cell envelope of Gram-negative bacteria, which features both inner and outer membranes with a thin peptidoglycan layer between the membranes [47,48]. Further analysis is required to determine the relative antibacterial efficacy of these surfaces against different bacterial genera, including examples of both Gram-positive and Gram-negative organisms.