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January 13, 2008
Unknown Bacteria
Bacteria, Despite its apparent simplicity contain a well-developed structure of the cell that is responsible for many of its unique biological properties Unknown Bacteria. . Many structural features are unique to the bacterium and is not among the archaea and eukaryotes Unknown Bacteria. Due to the relative simplicity of the bacteria to large agencies and the ease with which they can manipulate experimentally, the cell structure of the bacteria has been well studied, revealing many biochemical principles that have been applied to other agencies Unknown Bacteria.
Cell morphology
Bacteria come in a wide variety of the most basic structural shapes
Perhaps ownership of the bacteria is the cell morphology (shape) Bacteria unknown. Typical examples are:
- coccus (spherical)
- bacillus (rod)
- spirillum (spiral)
- filamentous
Cell Generally speaking, is characteristic of a particular bacterial species, but may vary depending on conditions growth of bacteria unknown. Some bacteria have complex life cycles involving the production of stems and appendages (and Bacteria.g Unknown Unknown Bacteria. Caulobacter) and some production structures to develop reproductive spores taking (and Bacteria.g Unknown Unknown Bacteria. Myxococcus, Streptomyces) Bacteria unknown. The bacteria usually distinctive form of cellular morphology when examined by light microscopy and various colony morphologies when grown in Petri plates Unknown Bacteria. These are often the first characteristics observed by a microbiologist to determine the identity of an unknown bacterial culture Unknown Bacteria.
The importance of cell size
Perhaps most obvious structural characteristic of the bacteria is (with some exceptions) small size Unknown Bacteria. For example, Escherichia coli, an "average" average size with the bacterium cell length of approximately Unknown Bacteria. 1 μ m cell has a volume of approximately 1 to 2 μ m3 Unknown Bacteria. This corresponds to a wet mass of approximately Unknown Bacteria. 1 pg, on the assumption that the cell consists mainly of water Unknown Bacteria. The dry mass of a single cell can be estimated as 20% of the wet mass, amounting to 0 pg Bacteria.2 Unknown Unknown Bacteria. About half of the dry weight of a bacterial cell consists of carbon, as well as about half of which is attributable to proteins Unknown Bacteria. Therefore, a typical fully grown 1 litre culture of Escherichia coli (an optical density of 1 Unknown Bacteria.0, corresponding to approximately Unknown Bacteria. 109 cells / ml) produces approximately Unknown Bacteria. 1 g wet mass Unknown Bacteria.
Small cell size is extremely important, since it allows a larger surface-to-volume ratio that allows for rapid distribution and intracellular uptake of nutrients and the excretion of waste Unknown Bacteria. In the area of low surface-to-volume ratios of the diffusion of nutrients and waste products through the bacterial cell membrane limits the speed at which the microbial metabolism can occur, at least the cell evolutionarily fit Unknown Bacteria. The reason for the existence of large cells is unknown, although it is speculated that the increase of cell volume is mainly used for the storage of excess nutrients Unknown Bacteria.
The bacterial cell wall
largely cells strength
The structure peptidoglycan Unknown Bacteria.
As In others, the bacterial cell wall provides structural integrity to the cell Unknown Bacteria. In prokaryotes, the primary function of the cell wall is the protection of cell turgor pressure inside caused by the much higher concentration of proteins and other molecules inside the cell compared with its external environment Unknown Bacteria. The bacterial cell wall differs from all other agencies by the presence of peptidoglycan (poly-N-acetylglucosamine and N-acetylmuramic acid), which is immediately outside the cytoplasmic membrane Unknown Bacteria. Peptidoglycan is responsible for the rigidity of the bacterial cell wall and for determining the shape of cells Unknown Bacteria. It is relatively porous and is not considered as a barrier for small permiability substrates Unknown Bacteria. While all the cell walls of bacteria (with some exceptions and Bacteria.g Unknown Unknown Bacteria. Intracellular parasites such as Mycoplasma) containing peptidoglycan, not all cell walls have the same general structure Unknown Bacteria. There are two main types of cell walls of gram-positive and gram-negative bacteria, which are differentiated by their features Gram staining Unknown Bacteria.
The Gram positive
The cell wall Gram positive cell wall is characterized by the presence of a peptidoglycan layer very thick layer, it is responsible for the maintenance of crystal violet dyes during the proceedings of Gram staining Unknown Bacteria. It is found exclusively in agencies belonging to the Actinobacteria (or high% G + C Gram-positive organisms) and Firmicutes (% or low G + C Gram-positive organisms) Bacteria unknown. Bacteria inside the Deinococcus-Thermus group also presented conduct Gram stain positive, but contains some structures of the typical cell wall of Gram negative organisms Unknown Bacteria. Embedded in the cell wall of Gram-positive are polyalcohols called teichoic acid, some of which are associated with lipid to form lipoteichoic acid Unknown Bacteria. Since lipoteichoic acid covalentemente are bound to the cytoplasmic membrane lipids are responsible for the linking of peptidoglycan to the cytoplasmic membrane Unknown Bacteria. Teichoic acids in the cell wall Gram positive a negative charge due to the presence of phosphodiester linkages between teichoic acid monomers Unknown Bacteria.
The cell wall of gram-negative cell wall
Unlike Gram-positive, Gram-negative cell wall peptidoglycan containing a thin layer Adjacent to the cytoplasmic membrane, which is responsible for cell wall 's inability to retain the crystal violet stain to fade with ethanol during Gram staining Unknown Bacteria. In addition to the peptidoglycan layer, the cell wall of gram-negative also contains an additional external compound membrane phospholipid and lipopolysaccharides faced in the external environment Unknown Bacteria. The highly charged nature of lipopolysaccharides confers a negative charge on the cell wall of Gram negative bacteria Unknown. The chemical structure of the outer membrane lipopolysaccharides is often concentrated in specific strains of bacteria (I Bacteria.e Unknown Unknown Bacteria. Sub-species) and is responsible for many of the antigenic properties of strains Unknown Bacteria.
The membrane
The bacterial cytoplasmic bacterial cytoplasmic membrane consists of a phospholipid bilayer and thus has all of the generals Duties of the cell membrane, such as acting permeability barrier for most of the molecules and acts as a location for transportation molecules in the cell Unknown Bacteria. In addition to these functions, prokaryotic membranes also in terms of energy conservation as the place on which a proton motive force is generated Unknown Bacteria. Unlike eukaryotes, bacteria membranes (with some exceptions and Bacteria.g Unknown Unknown Bacteria. Mycoplasma and methanotrophs) generally do not contain sterols Unknown Bacteria. However, many do contain microbes structurally related compounds called hopanoids likely to fulfil the same function Unknown Bacteria. Unlike eukaryotes, bacteria can have a variety of fatty acids within their membranes Unknown Bacteria. Along with the typical saturated and unsaturated fatty acids, fatty acid bacteria may contain more methyl or hydroxy groups cyclical Unknown Bacteria. The relative proportions of these fatty acids can be modulated by the bacterium to maintain optimal fluidity of the membrane (and Bacteria.g Unknown Unknown Bacteria. Next temperature change) Unknown Bacteria.
As a phospholipid bilayer, the portion of the membrane lipids Raincoat is external to molecules charged Unknown Bacteria. However, channels called porins are present in the outer membrane that can be transported liabilities of many ions, sugars and amino acids through the outer membrane Unknown Bacteria. These molecules are therefore present in the periplasm, Citoplasmáticas between the region and the outer membranes Unknown bacteria. The periplasm and peptidoglycan layer contains many proteins responsible for substrate binding or hydrolysis and extracellular signal reception Unknown Bacteria. The Periplásmico is believed to exist as a gel-like state instead of a liquid due to the high concentration of protein and peptidoglycan found within it Unknown Bacteria. Because of its location between the cytoplasmic membrane and external signals received and forced substrates are available to be transported across the cytoplasmic membrane using transport and signalling proteins embedded therein Unknown Bacteria.
Other structures of the surface Bacterial
Fimbrae and Pili
main article: Pilus
Fimbrae proteins are tubes that extend beyond the outer membrane of many members of the Bacteria Proteobacteria unknown. They are generally short-lived and now in large numbers all around the bacterial cell surface Unknown Bacteria. Fimbrae generally function to facilitate the setting of a bacterium to a surface (and Bacteria.g Unknown Unknown Bacteria. Forming a biofilm) or other cells (and Bacteria.g Unknown Unknown Bacteria. Animal cells during pathogenesis)) Unknown Bacteria. Some agencies (and Bacteria.g Unknown Unknown Bacteria. Myxococcus) fimbrae use of motility to facilitate the assembly of multicellular structures like fruiting bodies Unknown Bacteria. Pili are similar in structure to fimbrae but are much larger and more present in the bacterial The low number of cells Unknown Bacteria. Pili involved in the process of bacterial conjugation Unknown Bacteria. No sex pili also help bacteria on the surface of grip Unknown Bacteria.
S-layers
main article: layer
An S-S-is a layer of cells on the surface layer of proteins found in many different bacteria and archaea, it serves some of the cell wall of bacteria unknown. All S-layers are formed by a two-dimensional matrix of proteins and has a crystalline appearance, the symmetry of which differs among species Unknown Bacteria. The exact role of S-layers is unknown, but it has been suggested that act as a barrier permeability partial substrates great unknown bacteria. For example, an S-layer could keep extracellular proteins near the cell membrane by preventing Its circulation outside of the cell Unknown Bacteria. In some pathogenic, an S-layer can help facilitate survival in the host by conferring protection against host defense mechanisms Unknown Bacteria.
Capsules and Slime Layers
main article: Slime layer
Many bacteria secrete Polymers Extracellular outside their cell walls of bacteria unknown. These polymers are generally composed of proteins and polysaccharides sometimes unknown bacteria. Capsules are relatively impervious structures that can not be stained with dyes such as India ink Unknown Bacteria. They are generally involved in the attachment of bacteria to other cells or inanimate surfaces to form biofilms Unknown Bacteria. Slime layers are somewhat larger structures that help protect the bacteria from phagocytosis and desiccation Unknown Bacteria.
Flagella
A-Monotrichous; B-Lophotrichous; Amphitrichous C-, D-Peritrichous;
Main Article: Flagellum
Perhaps most recognizable extracellular bacterial cell structures are scourges Unknown Bacteria. Flagella are whip-like structures out of the bacterial cell wall and are responsible for bacterial motility (Unknown Unknown Bacteria Bacteria.e. Circulation) Bacteria unknown. The disposition of the Flagelos about the bacterial cell is unique to the species observed Unknown Bacteria. Common forms include:
- Peritrichous - multiple scourges found in several places around the cell
- Polar - Single scourges found in one or both cell poles
- Lophotrichous - A tuft of evils found in a cell pole
Flagella are complex structures which are composed of different protein Unknown Bacteria. Flagellin These include, which is the whip-and as a tube of a protein complex that spans the cell wall and cell membrane to form an engine What causes the scourge of rotating Unknown Bacteria. This rotation is usually driven by proton motive force and can be found in the body of the cell Unknown Bacteria.
Intracellular structures of the bacterial cell
Prokaryote of eukaryotic cells for structure
In comparison, the characteristics of intracellular bacteria cells are extremely simplistic Unknown Bacteria. Bacteria do not contain organelles in the same sense as Unknown Bacteria eukaryotes. By contrast, chromosome and perhaps the only ribosomes are easily observable intracellular structures found in all bacteria Unknown Bacteria. There exist, however, the focus groups of bacteria that contain more complex intracellular structures, some of which are discussed below Unknown Bacteria.
The chromosome and bacterial plasmids
main article: Plasmid
Unlike eukaryotes, the bacterial chromosome is not enclosed within a core membrane, but instead lies within the cytoplasm Bacteria bacterial unknown. This means that the transfer of information through cellular processes translation, transcription and DNA replication occur all in the same compartment and can interact with other cytoplasmic structures, in particular ribosomes Unknown bacteria. The bacterial chromosome packaging is not using Histonas to form chromatin in eukaryotes, but exists as a very compact supercoiled structure, the exact nature of which remains unclear Unknown Bacteria. Bacterial Most of the chromosomes are circular, although some examples of linear chromosomes exist (and Bacteria.g Unknown Unknown Bacteria. Borrelia burgdorferi) Bacteria unknown. Along with the chromosomal DNA, most of the bacteria also contain small independent pieces of DNA called plasmids encode for that often the traits that are advantageous, but not essential for their host bacterial Unknown Bacteria. Plásmidos can easily be won or lost by a bacterium and can be transferred between bacteria as a form of horizontal gene transfer Unknown Bacteria.
Ribosomes and other multiprotein complex
main article: Ribosome
In most of the more numerous intracellular bacteria is the structure of the ribosome, the site of protein synthesis in all living organisms Unknown Bacteria. All Procariotas have 70S (where S = Svedberg units), while the largest contain eukaryotic ribosomes in their cytosol Unknown bacterial 80S ribosome. The 70S ribosome is composed of a subunit 50S and 30S Unknown bacteria. The subunit contains the 23S and 50S rRNA 5S while the 30S subunit contains the Unknown Bacteria 16S rRNA. RRNA These molecules differ in size in eukaryotes are complex and a large number of ribosomal proteins, the number and type of which may vary slightly among agencies Unknown Bacteria. While the ribosome is the most commonly observed Multiprotein complex intracellular bacteria in other large complexes and indeed sometimes, can be viewed using microscopy Unknown Bacteria.
Intracellular membranes
While not typical of all the microbes that contain many intracellular bacteria also of the membranes (or extensions) Unknown Bacteria their cytoplasmic membranes. These membranes normally function to maximize the amount of membrane available for the use of membrane processes in the energy performance, much the same as they do in mitochondria and chloroplasts Unknown Bacteria. Examples of intracellular bacteria containing membranes are fototrofas, nitrifying bacteria and methane-oxidizing bacteria Unknown Bacteria. Membranes are also in intracellular bacteria belonging to the group Planctomycetes little studied, despite these membranes are more akin organellar membranes in eukaryotes and are currently unknown unknown function Bacteria.
Cytoskeleton
main article: Prokaryotic cytoskeleton
The cytoskeleton The name is prokaryotic collective of all structural filaments in prokaryotes Unknown Bacteria. It was once thought that prokaryotic cells lacked cytoskeletons, but recent advances in the technology for displaying the structure and the determination shown by the fact filaments exist in these cells Unknown Bacteria. In fact, Homologues of the major proteins of cytoskeleton in eukaryotes have been found in prokaryotes Unknown Bacteria. Cytoskeletal components play crucial roles in cell division, protection, how determination and the establishment of polarity in various prokaryotes Unknown Bacteria.
Nutrient storage structures
Most bacterial habitats do not live in environments containing large amounts of essential nutrients at all times unknown bacteria. To accommodate these transient levels of bacteria contain several nutrients different methods of storing nutrients in times of plenty for use during times of want Bacteria unknown. For example, many bacteria Storing excess carbon in the form of glycogen Unknown polyhydroxyalkanoates or bacteria. Some microbes store soluble nutrients such as nitrates in vacuoles Unknown Bacteria. Sulfur most cases is stored as elementary (S0) granules that can be deposited either intra-or extracellular Unknown Bacteria. Sulfur granules are especially common in bacteria that use hydrogen sulfide as a source of electrons Unknown Bacteria. Most of the examples mentioned above can be seen using a microscope and are surrounded nonunit a thin membrane separating the cytoplasm Unknown Bacteria.
Gas vesicles
Gas Vesicular are spindle-shaped structures found in some planktonic bacteria which provides buoyancy to these cells by decreasing its overall density of cells Unknown Bacteria. They are formed by a layer of protein that is highly impervious to solvents such as water, but permeable to most of the gas Unknown Bacteria. By adjusting the amount of gas present in vesicles their gas bacteria may increase or decrease its overall density of cells and thus move up or down in the water column to maintain its position in an optimal environment for Unknown growth Bacteria.
Carboxysomes
main article: Carboxysome
Carboxysomes intracellular structures that are found in many autotrophic bacteria as cyanobacteria, Knallgasbacteria, Nitroso-and Nitrobacteria Unknown Bacteria. They Proteínico structures resemble the heads of phage in its morphology and contain enzymes for the fixation of carbon dioxide in these agencies (especially ribulose bisphosphate carboxylase / Oxigenasa, RuBisCo, and carbonic anhydrase) Bacteria unknown. It is believed that the high local concentration of enzymes, along with the rapid conversion of bicarbonate of carbon dioxide by carbonic anhydrase allows faster and more efficient than the fixation of carbon dioxide inside the cytoplasm possible Unknown Bacteria.
Similar Structures are known to harbour coenzyme B12-dehydratase containing glycerol, the key enzyme for the fermentation of glycerol 1.3-propandiol in some Enterobacteriaceae (e Unknown Bacteria. G Unknown Bacteria. Salmonella) Unknown Bacteria.
Magnetosomes
Main Article: Magnetosome
Magnetosomes are intracellular structures found in magnetotactic bacteria that enable them to sense and joined along a magnetic field (magnetotaxis) Bacteria unknown. The ecological role of magnetotaxis unknown, but is assumed to participate in the determination of optimal concentrations of oxygen Unknown Bacteria. Magnetosomas are composed of minerals magnetite and are surrounded by a membrane nonunit Unknown Bacteria. Magnetosomas The morphology of each species, is unknown Bacteria.
Endospores
main article: Endospores
Perhaps the best known bacterial adaptation to stress is the formation of Endoesporas Unknown Bacteria. Endospores are bacterial survival structures that are highly resistant to many different types of chemicals and environmental stresses, and thus allow the survival of the bacteria in environments that would be lethal to these cells as normal vegetative Unknown Bacteria. It has been proposed Endospore training that has allowed the survival of some bacteria for hundreds of millions of years (and Bacteria.g Unknown Unknown Bacteria. Crystals of salt) although these publications have questioned Unknown Bacteria. Endospore Training is Merely several genres of Gram-positive bacteria, such as Bacillus and Clostridium Unknown Bacteria. It differs from reproductive spores that only one of spores is formed by cells in a manner which avoids net gain in the number of cells to germination endospore Unknown Bacteria. The location of a endospore Inside a cell is specific to the species and can be used to determine the identity of an unknown bacterium Bacteria.
