Bacterial cell shape

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. 

Vibrio (i) Curved, rod-shaped bacterial cell, (ii) Bacterium of the genus Vibrio. Virion Virus particle the virus nucleic acid surrounded by protein coat and in some cases other material. 

The processes of electron transport and oxidative phosphorylation are membrane-associated. Bacteria are the simplest life form, and bacterial cells typically consist of a single cellular compartment surrounded by a plasma membrane and a more rigid cell wall. In such a system, the conversion of energy from NADH and [FADHg] to the energy of ATP via electron transport and oxidative phosphorylation is carried out at (and across) the plasma membrane. In eukaryotic cells, electron transport and oxidative phosphorylation are localized in mitochondria, which are also the sites of TCA cycle activity and (as we shall see in Chapter 24) fatty acid oxidation. Mammalian cells contain from 800 to 2500 mitochondria other types of cells may have as few as one or two or as many as half a million mitochondria. Human erythrocytes, whose purpose is simply to transport oxygen to tissues, contain no mitochondria at all. The typical mitochondrion is about 0.5 0.3 microns in diameter and from 0.5 micron to several microns long its overall shape is sensitive to metabolic conditions in the cell. 

Klebsiella pneumoniae was is Jated as a representative microorganism from produced water. The bacterium was starved in phosphate buffer salts solutions at concentrations of either 10 /ml or 10 /ml. During starvation periods of up to 24 days the bacterial cells changed in size and shape from rod-shaped, up to 2.2 ym long,... 

An important molecular target of the B-lactam antibiotics is an enzyme that acts as a transpeptidase in the stepwise polymerization leading to a thickened, strong bacterial cell wall. Several amino acids are present in addition to the terminal -alanyl- -alanyl unit which the Strominger hypothesis suggests has the same overall shape and reactivity as... 

Light microscopy can be used to detect particles with regular shapes (e.g., crystals) and microbes like yeast and bacterial cells (Glenister, 1971). Microscopy can also detect some irregular particles such as diatomaceous earth or adsorbents (Glenister, 1974). It is much less informative with amorphous particle hazes. The use of specific stains can, however, provide useful information. An excellent book by Glenister (unfortunately no... 

Biological samples such as bacteria and viruses have been studied by SdFFF as well as FIFFF. These two techniques provided bacterial number, density, size, and mass distributions of bacterial cells of diverse shapes and sizes, molecular weights, sizes, densities, and diffusivities of viruses. SdFFF has been used to analyze protein particles, including casein derived from nonfat dry milk, albumin microspheres, and particles in cataractous lenses originating from the aggregation of lens proteins. 

Bacterial cells share certain common structural features, but also show group-specific specializations (Fig. 1-6). E. coli is a usually harmless inhabitant of the human intestinal tract. The E. coli cell is about 2 prri long and a little less than 1 prri in diameter. It has a protective outer membrane and an inner plasma membrane that encloses the cytoplasm and the nucleoid. Between the inner and outer membranes is a thin but strong layer of polymers called peptidoglycans, which gives the cell its shape and rigidity. The plasma membrane and the... 

In terms of shape, the first of these are rod-shaped and are called bacilli (singular, bacillus). The bacilli often have small, whip-like structures known as flagella, with which they are able to move about. Some bacilli have oval, egg-shaped, or spherical bodies in their cells, known as spores. Under adverse conditions, such as dehydration, and in the presence of disinfectants, the bacteria may die, but the spores may be able to live on. The spores germinate when the conditions become favorable, and form new bacterial cells. Some are so resistant that they can withstand boiling and freezing temperatures and prolonged desiccation. See Fig. 1. 

A second type of bacteria is the cocci (singular, coccus) which are spherical or ovoid in shape. The individual bacterial cells of this group may occur singly [Micrococcus), in chains (Streptococcus), in pairs [Diplococcus). in irregular bunches (Staphylococcus), and in the form of cubical packets (Sarcina). The coccus does not form spores and usually is nonmotUe. See Fig. 2. 

Shapes Bacteria are unicellular microscopic organisms. There are about 1,500 known species occurring in practically all natural environments. The typical diameter of the cell ranges from 0.5 to 1 fjm. The lengths of bacterial cells vary greatly. Bacteria occur in a variety of shapes such as ... 

Stewart GC. Taking shape control of bacterial cell wall biosynthesis. Mol Microbiol. 2005 57 1177-1181. 

Hewitt et al. [167] have exploited flow cytometry to quantify the impact of fluid mechanical stress on bacterial cultures. A modified technique, called the slit-scan method, allows the determination of cell shapes and of intracellular location of stained components [34]. Image cytometry and fluorescence microscopy are variants for determination of the volume growth of cells or morphology changes and seem to have become increasingly important [60,382,461 ]. 

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