Bacterial cell outer surface

Carbohydrates related to membranes can be found as lipopolysaccharides or as parts of glycoproteins. Sugars are often characteristic determinants of cell surfaces (see below). The great majority of carbohydrates are found in the outer leaflet of a membrane, resulting in an asymmetrical structure. This is especially true for many plasma membranes and the outer membrane of Gram-negative bacterial cells (see below). 

Cells of mycoplasmas sometimes grow as filaments but are often spherical and as small as 0.3 micrometer (pm) in diameter. Their outer surface consists of a thin cell membrane about 8 nanometers (nm) thick. This membrane encloses the cytoplasm, a fluid material containing many dissolved substances as well as sub-microscopic particles. At the center of each cell is a single, highly folded molecule of DNA, which constitutes the bacterial chromosome. Besides the DNA there may be, in a small spherical mycoplasma, about 1000 particles 20 nm in diameter, the ribosomes. These ribosomes are the centers of protein synthesis. Included in the cytoplasm are many different kinds of... 

It serves to control the passage of small molecules into and out of the cell. Its outer surface carries receptors for recognition of various materials. The inside surface of bacterial membranes contains enzymes that catalyze most of the oxidative metabolism of the cells. Bacterial cell membranes are sometimes folded inward to form internal structures involved in photosynthesis or other specialized reactions of metabolism such as oxidation of ammonia to nitrate.2 In E. coli replication of DNA seems to occur on certain parts of the membrane surface, probably under the control of membrane-bound enzymes. The formation of the new membrane which... 

The outer surfaces of bacteria are rich in specialized polysaccharides. These are often synthesized while attached to lipid membrane anchors as indicated in a general way in Eq. 20-20.136/296a One of the specific biosynthetic cycles (Fig. 20-9) that depends upon undeca-prenol phosphate is the formation of the peptidoglycan (murein) layer (Fig. 8-29) of both gram-negative and gram-positive bacterial cell walls. Synthesis begins with attachment of L-alanine to the OH of the lactyl... 

To be presented on the surface of a bacterial cell, the protein of choice, after having been synthesized in the cytoplasm, has to pass the cytoplasmic and the outer membrane. This is generally achieved by genetically fusing the passenger protein... 

TERS experiments were performed to study the bacterial cell surface. Biju et al. combined silver island films on glass coverslips with an AFM to investigate the effect of electron-acceptor limitation on the outer cell membrane of Shewanella one.ide.nsis [103]. 

The dogma that glycoproteins occur exclusively in eucaryotic cells had to be revised in the last twenty years. Bacterial glycoproteins form the outer surface (S)-layer of archae- and eubacteria [61,62]. In analogy to eucaryotic cells, partly sulfated oligosaccharides attached to Asn or Thr are found in halobacteria. Nucleoside-diphosphate-activated oligosaccharides were identified as intermediates in the biosynthesis of the S-layer of the eubacterium Bacillus alvei [63] and the archaebacterium Methanothermus fervidus [64],... 

In contrast to mammalian cells, the membrane of bacterial cells is much more complex and, as in the case of Escherichia coli or mycobacteria, it is asymmetric (see Section 1.2.2). The reason for this is that these small cellular life forms depend on diffusion of nutrients and metabolites. All substrates going in and out of the cell must diffuse through their cell walls. This might be one reasons why the surface area to volume ratio is important for bacterial cell shapes. This ratio is determined by the structure of their outer cell wall. To cross such a barrier, mainly by passive diffusion, chemotherapeutics must have other properties in addition to those necessary for suitable pharmacokinetics in the host, as in most cases, the target of the chemotherapeutics is within the cytoplasm. 

Bos, M.P., Tefsen, B., Geurtsen, J., Tommassen, J. Identification of an outer membrane protein required for the transport of lipopolysaccharide to the bacterial cell surface. Proc Natl Acad Sci... 

Positively charged photosensitizers, particularly cationic metallophthalocy-anines, have been proved to be most efficient in photodynamic inactivation of both Gram-negative and -positive bacteria. The reason is believed to lie in the electrostatic interaction of cationic photosensitizer with negatively charged sites at the outer surface of the bacterial cell wall, which facilitates the photosensitizer molecule binding to bacterial cells. 

The first stage in the action of an antibiotic or biocide on a bacterial cell involves interaction between the chemical and the biological entity. Adsorption of a variety of biocides into bacterial cells has been described [33] but this, per se, does not necessarily provide information about the mechanism or site of action of the antibacterial compound. However, resistant cells would usually (but not necessarily) be expected to adsorb less of a chemical than sensitive cells. In non-sporulating bacteria, changes to the outer layers of cells may follow the initial binding to the cell surface or there may be diffusion across the cell envelope in either case, an antibiotic or biocide will penetrate the cell to reach the primary site of action at the cytoplasmic membrane or within the cytoplasm. Little is known about the penetration of antibacterial agents into bacterial spores. 

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