Bacteria internal structure

Physically, all these prokaryotes are small, diameter about 1.0 pm and are of rigid, simple shape. They usually have little or no internal structure so that chemical diffusion is relatively rapid. Secondary compartments are rare but vesicles and vacuoles (even nuclei) are found in a very few large bacteria. We shall see that all the prokaryote cells have controlled, autocatalytic, internal metabolism, but are relatively little affected by external circumstances, except by shortage of nutrients. 

Internal structure of the tube worm Riftia pachyptila. (a) Oxygen, sulfide, and carbon dioxide are absorbed through the plume filaments and transported In the blood to the cells of the trophosome. (b) The chemicals are absorbed into these cells, which contain dense colonies of sulfur bacteria, where they are converted to organic compounds and (c) passed back into the circulatory system to act as an energy source for the worms. Source-. From Childress, J. J., et al. (1987). Scientific American, 256, 114-121. 

Like living organisms themselves, cells come in a remarkable variety of flavors. Brown has described what might be a human cell with elaborate internal structure. However, there is no such a thing as a typical cell. Afunctional liver cell, a hepatocyte, is quite distinct from a nerve cell, a neuron, that, in turn, is not much like a cell of the retina of the eye. Skin cells, pancreatic cells, kidney cells, cells of the testis and ovary, red blood cells, bone cells, and on and on, are all structurally, functionally, and metabolically distinct. Indeed, there are several types of cells in the skin, pancreas, kidney, testis, ovary, and bone. Then there are the cells of bacteria and other microorganisms that have no nucleus or other membrane-limited organelles very different. Diversity abounds. 

The presence of fungal endophytes within healthy tissue of vegetables was first described in 1904 (Tan and Zou,2001). Work performed by Samish and Etinger-Tulczynsha (1962) suggested that bacterial endophytes also existed within plants although this was disputed for many years (Lund, 1992). However, it has only recently been accepted that bacteria can indeed reside in the internal structures of undamaged plants (Rosenblueth and Martinez-Romero, 2006 Schulz and Boyle, 2005). 

Generalized representations of the internal structures of animal and plant cells (eukaryotic cells). Cells are the fundamental units in all living systems, and they vary tremendously in size and shape. All cells are functionally separated from their environment by the plasma membrane that encloses the cytoplasm. Plant cells have two structures not found in animal cells a cellulose cell wall, exterior to the plasma membrane, and chloroplasts. The many different types of bacteria (prokaryotes) are all smaller than most plant and animal cells. Bacteria, like plant cells, have an exterior cell wall, but it differs greatly in chemical composition and structure from the cell wall in plants. Like all other cells, bacteria have a plasma membrane that functionally separates them from their environment. Some bacteria also have a second membrane, the outer membrane, which is exterior to the cell wall. 

More recently, a closer prokaryotic homolog of actin was characterized. This protein, called MreB, plays an important role in determining cell shape in rod-shaped, fdamentous, and helical bacteria. The internal structures formed by MreB are suggestive of the actin cytoskeleton of eukaryotic cells, although they are far less extensive. Even though this protein is only approximately 15% identical in sequence with actin, MreB folds into a very similar three-dimensional structure. 

Green, iron-rich structures called rusticles growing from the sunken hull of RMS Titanic are gradually destro5ung what remains of the ship. Rusticles contain colonies of metallophilic bacteria the structures are composed externally of lepidocrocite, y-Fe(0)0H, and internally of goethite, a-Fe(0)0H. The rate at which the bacteria are converting the ship s hull into rusticles is alarming and the phenomenon is a topic of current research. 

Naturally occurring molecular ensembles such as proteins from photosynthetic systems (plants, algae, photosynthetic bacteria, etc) are usually relatively rigid systems that contain various chromophores and hold them at fixed positions and orientations relative to each other. That is why, despite the numerous energy jumps between the chromophores, the resulting emitted fluorescence is polarized. The extent of this polarization thus affords invaluable information about the internal structure of molecular complexes. 

Cells are of small volume, varying over considerable ranges. With many bacteria, for example, the linear dimensions run from 0 1 to 10/i. The shape may be spherical, roughly cylindrical, or more complicated. The internal structure varies some contain a well-defined central core or nucleus, while in others the nucleus, if it exists, is only faintly differentiated and requires special methods to... 

Bacteria when grown on a semisolid agar medium forms a characteristic type of colony which differs in size, shape, surface, elevation, internal structure, colour, opacity and consistency. Typical colony morphologies are shown in Fig. 13.25. 

Prokaryote Micro-organism that lacks a cell nucleus and membrane-enclosed internal structures, all bacteria in the kingdom Monera (Prokaryotae) are prokaryotes. 

Rieske protein is essential in the respiratory electron transport in mitochondria, chloroplasts and some bacteria. Its structure is quite different from other proteins containing [Fe2S2] in so far as the iron atom in Rieske protein is coordinated to two cysteines and two histidines. Miinck et al. investigated the EFG tensor of the ferrous site and found a fast relaxation between the two Zeeman levels of the S = 1/2 Kramers doublet leading to a diminished internal hyperfine field and a quasidiamagnetic spectrum in a filed of 4 T at 200 K, which is an indication of a magnetic splitting due to external field. ... 

The predominant bacteria were A. pasteurianus, and a novel species was found and named A. ghanensis (Cleenwerck et al. 2007), A. senegalensis (Camu et al. 2007 Ndoye et al. 2007), and A. fabarum (Cleenwerck et al. 2008). Acetic acid can penetrate the cocoa beans, kill the embryo, and decompose their internal structure to form flavor and color development. Thus, acetic acid bacteria have an important function during cocoa bean fermentation that contributes to the formation of cocoa flavor precursors and the control of the cocoa bean fermentation process. 

In spite of the variety of appearances of eukaryotic cells, their intracellular structures are essentially the same. Because of their extensive internal membrane structure, however, the problem of precise protein sorting for eukaryotic cells becomes much more difficult than that for bacteria. Figure 4 schematically illustrates this situation. There are various membrane-bound compartments within the cell. Such compartments are called organelles. Besides the plasma membrane, a typical animal cell has the nucleus, the mitochondrion (which has two membranes see Fig. 6), the peroxisome, the ER, the Golgi apparatus, the lysosome, and the endosome, among others. As for the Golgi apparatus, there are more precise distinctions between the cis, medial, and trans cisternae, and the TGN trans Golgi network) (see Fig. 8). In typical plant cells, the chloroplast (which has three membranes see Fig. 7) and the cell wall are added, and the lysosome is replaced with the vacuole. 

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