Bacteria cell envelope

The mode of action of starch capped copper nanoparticles (SCuNPs) was compared with that of the well-known antibiotic amphicillin (Fig. 9). There was a drastic decrease in the optical density of compounds containing SCuNPs and ampicillin, ultimately reaching almost zero suggesting that there were no more bacteria present in the culture. AmpiciUin at a concentration of 100 pg/ml has the ability to lyse E.coli almost immediately [29]. The same effect was produced by SCuNPs at 365 ng/ml concentration. The cell lysis occurs at the expense of the fact that at the point of cell division there occurs a deformation of the cell envelope. The decrease in optical density is possibly associated with the cell-envelope deformation occurring at the point of cell division [30]. 

Cell envelopes of prokaryotic organisms (archaea and bacteria) are characterized by the presence of two distinct components the cytoplasmic membrane, which constitutes the inner layer, and an outer supramolecular layered cell wall (for reviews see Ref. 4), which pre-... 

Studies on S-layers present on the cell envelopes of a great variety of pathogenic organisms [100] revealed that these crystalhne arrays can represent important virulence factors. Most detailed studies have been performed on the fish pathogenic bacteria Aeromonas salmonicida and Aeromonas hydrophila [102] and the human pathogen Campylobacter fetus uh p. fetus [103] and Bacillus anthracis [104]. For example, whole-cell preparations or partially purified cell products are currently used as attenuated vaccines against various fish pathogens [102,105]. 

In general, virus receptors carry out normal functions in the cell. For example, in bacteria some phage receptors are pili or flagella, others are cell-envelope components, and others are transport binding proteins. The receptor for influenza vims is a glycoprotein found on red blood cells and on cells of the mucous membrane of susceptible animals, whereas the receptor site of poliovirus is a lipoprotein. However, many animal and plant viruses do not have specific attachment sites at all and the vims enters passively as a result of phagocytosis or some other endocytotic process. 

Vecchio A, Finoli C, Simine DD, Andreoni V (1998) Heavy metal biosorption by bacterial cells. Fresenius J Anal Chem 361 338-342 Walker SG, Flemming CA, Ferris FG, Beveridge TJ, Bailey GW (1989) Physicochemical interaction of Escherichia coli cell envelopes and Bacillus subtilis cell walls with two clays and ability of the composite to immobililze heavy metals from solution. Appl Environ Microbiol 55 2976-2984 Wightman PG, Fein JB (2001) Ternary interactions in a humic acid-Cd-bacteria system. ChemGeol 180 55-65... 

In Gram-negative bacteria which are characterised by a rather complex cell envelope, the CM is also referred to as inner membrane to distinguish it from a second lipid bilayer, termed outer membrane (OM). The space between these two layers is called the periplasm (PP). In the periplasmic space, many proteins are found with a variety of functions. Some are involved in biosynthesis and/or export of cell wall components and surface structures (e.g. pili, flagellae,... 

Interestingly, CNTs have been shown to be able to deliver exogenous genes not only in mammalian cells, but also in bacteria. Rojas-Chapana et al. (2005) demonstrated that oxidised, water-dispersible CNTs can deliver pDNA into E. coli (ratio of transformation efficiency/transformants of about 32) by opening up temporary nanochannels across the cell envelope. The authors described that addition of CNTs in a suspension containing E. coli and pDNA and application of a microwave frequency resulted in the orientation of the CNT tips perpendicularly to the cell surface and subsequently plasmid delivery into the bacteria. 

The observed adjuvanticity of Bordetella pertussis is largely attributable to the presence of pertussis toxin and lipopolysaccharide (LPS). LPS, a constituent of the cell envelope of Gramnegative bacteria (Chapter 3), essentially consists of polysaccharide moieties to which lipid (lipid A) is covalently attached. 

Alternatively, /cuptake, may represent the rate constant associated with transfers from immediately outside the cell to the interior spaces where the relevant enzymes occur. In this case, we need to focus on how long it takes for microorganisms to be equilibrated with medium in which they occur (step 1 in Fig. 17.1). This requires an evaluation of the time for chemicals to be transported from the outside of the microorganisms across their cell envelope to the relevant enzymes. The cell envelope of bacteria differs from species to species (Sikkema et al., 1995) and can even be changed by a single microbial strain in ways that affect cross-membrane transport in response to environmental conditions (e.g., Pinkart et al., 1996 Ramos et al., 1997). However, a general description is useful in the context of molecular... 

Peptidoglycan Hetero- peptides attached 4)Mur2Ac(j81—>4) GlcNAc(j31 Very large Structural in bacteria, gives rigidity and strength to cell envelope... 

Neither the mechanisms of the host defence for eradication of challenging Salmonella bacteria, nor the relative importance of the host defence against the various Individual surface components of the bacterial cell envelope are well understood. Since, as was stated above, the O-antlgenic polysaccharide chains apparently play an important role in eliciting an effective host defence of either humoral or cellular nature, we have used the various saccharides described earlier for studies of this problem. 

Successful infection proceeds simultaneously with nodule morphogenesis triggered by the signal compounds produced by Rhizobium in response to its host, and leads to the release of bacteria from the infection threads into the cortical cells. Concomitantly, the bacteria are enveloped in a host-derived plasma membrane called the peribacteroid membrane (PBM) (Verma et al., 1978 Robertson et al., 1978). Both host- and bacterium-derived proteins are specifically targeted to this membrane (Fortin et al., 1985, 1987 Katinakis Verma, 1985 Katinakis et al., 1988), making it a unique subcellular compartment. 

Cells are broadly classified as either eukaryotes or prokaryotes (see Appendix 3). Both types have a membrane, known as the cytoplasmic or plasma membrane (see Appendix 3), that separates the internal medium (intracellular fluid) of the cell from the external medium (extracellular fluid). Cytoplasmic membranes may also divide the interior of a cell into separate compartments. In addition to the cytoplasmic membrane, the more fragile membranes of plants and bacteria are also protected by a rigid external covering known as a cell wall. The combination of cell wall and plasma membrane is referred to as the cell envelope (Appendix 2). 

Antibacterial antibiotics normally act by either making the plasma membrane of bacteria more permeable to essential ions and other small molecules by iono-phoric action or by inhibiting cell wall synthesis (see section 7.2.2). Those compounds that act on the plasma membrane also have the ability to penetrate the cell wall structure (Appendix 3). In both cases, the net result is a loss in the integrity of the bacterial cell envelope, which leads to irreversible cell damage and death. 

Figure A2.1 Schematic cross-sections of the cell envelopes of (a) Gram-positive and (b) Gramnegative bacteria...

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