Свойство:Cell Structure
Материал из Поле цифровой дидактики
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A
Acetobacter is an obligatory aerobic, nitrogen-fixing bacteria that is known for producing acid as a result of metabolic processes. While all nitrogen-fixing bacteria contain nitrogenase in order to utilize atmospheric nitrogen gas as a source for metabolic biosynthesis, different nitrogen-fixing microorganisms protect the oxygen-sensitive microorgansims from oxygen exposure in different ways. A. diazotrophicus has been called interesting because it carries out nitrogen fixation under aerobic conditions. It needs oxygen for the production of large quantities of ATP required for nitrogen fixation; however, little is known about the mechanism or system that protects the nitrogenase under aerobic conditions. A. diazotrophicus is a plant endophyte and has been said to be capable of excreting about half of its fixed nitrogen in a form that plants can use. +
The cells of Acidilobus are regular or irregular cocci with diameter of 1-2 µm. They are non-motile and have a cell envelope consisting of one S-layer attached to the cytoplasmic membrane. The S-layer composes of a single layer of subunits covered with a thin osmophilic layer that may be naturally proteinaceous.
It ferments starch and forms acetate as the main growth product (other growth substrates are yeast extract, beef extract and soya extract). Elemental sulfur stimulates growth on yeast, soya, and beef extracts and is reduced to H2S. The organism is unable to utilize acetate, arabinose, cellulose, formate, fructose, galactose, glucose, glycine, guar gum, lichenan, malate, maltose, methanol, pectin, pyruvate, propionate, xylan, xylose, and mixture of amino acids. +
Acinetobacter cells are Gram-negative short rods (coccobacilli), measuring 1.0-1.5 by 1.5-2.5 microns during growth; they often become more coccoid during the stationary phase. Cells are found in pairs or small clusters; the groups form smooth, pale colonies on solid media. All species are strictly aerobic, catalase positive, and oxidase negative; it is the last test which is most used to distinguish Acinetobacter from other infective bacteria. These bacteria can use a varied selection of organic materials as sources of carbon. +
During times of low environmental nitrogen, about one cell out of every ten will differentiate into a heterocyst. Heterocysts then supply neighboring cells with fixed nitrogen in return for the products of photosynthesis, that they can no longer perform. This separation of functions is essential because the nitrogen fixing enzyme in heterocysts, nitrogenase, is unstable in the presence of oxygen. +
B
When an infected tick feeds on a vertebrate host, the Babesia parasite enters the host in trophozoite ("ring") form. The trophozoites invade the host's red blood cells, where they multiply through binary fission. It is here that the merozoite form of Babesia wreaks the most havoc on the host, as it destroys red blood cells and causes anemia. Uninfected ticks ingest the vertebrate's blood when feeding, and the merozoitic parasites settle in the midgut. After multiplying in the vector's gut, Babesia migrates to the salivary glands, ready to be spread to a new vertebrate host. Like all apicomplexans, Babesia's cells invade the host's red blood cells by way of the apicoplast, an organelle unique to members of this phylum. See Apicomplex for more details. +
Diatoms are set up with a cell wall made up of silica and the diatom itself is a single-celled photosynthetic protist. Very little is known about how the cell wall is made, but scientists are researching it to hopefully find a way to reproduce the thin glass-like wall for nanotechnology. Diatoms are autotrophs, which means that they are able to produce their own sugars, lipids and ameno acids. During asexual reproduction, the diatom cell size progressively decreases as each valve produces a smaller complementary valve. When the smaller valves have completely formed the two cells must divide; but because one side of the the diatom is smaller, when they split one is the same size as the original, while one is smaller yet. When they shrink to a certain size, they have to reproduce sexually. To do this they develop an auxospore which then will become a diatom (see diagram above). +
Полезные бактерии, или пробиотики — это микроорганизмы, которые доказано приносят пользу. К самым распространенным относятся лакто- и бифидобактерии. Продукты с пробиотиками — по сути, продукты (или добавки), которые содержат полезные бактерии.Bifidobacterium is a Gram-positive, anaerobic, branched rod-shaped bacterium. In the intestines, they ferment sugars to produce lactic acid. The B. longum genome codes for many proteins specialized for the catabolism of oligosaccharides. This bacterium also is able to use so-called "nondigestible" plant polymers or host-derived glycoproteins and glycoconjugates; it is thought that Bifidobacterium's ability to compete with other gastrointestinal bacteria and occupy a large percentage in the bacterial flora of the gastrointestinal region might be partly due to the large variety of molecules that it is able to use for energy +
C
Both Chlamydia trachomatis and Chlamydia pneumoniae are Gram-negative (or at least are classified as such, they are difficult to stain, but are more closely related to Gram-negative bacteria), aerobic, intracellular pathogens. They are typically coccoid or rod-shaped and require growing cells to remain viable. Chlamydia cannot synthesize its own ATP, and can also not be grown on an artificial medium, and consequently was once thought to be a virus. The unique cell wall of Chlamydia trachomatis is thought to be one of its virulence factors, as it inhibits phagolysosome fusion in phagocytes. The cell wall contains an outer lipopolysaccharide membrane but lacks peptidoglycan. It instead contains cysteine-rich proteins that are likely the functional equivalent of peptidoglycan. This unique cell wall structure, allows for intracellular division and extracellular survival. +
M
Micrococcus are Gram-positive cocci that are 0.5 to 3.5 micrometers in diameter and usually arranged in tetrads or irregular clusters. They are generally strict aerobes and can generally reduce nitrate. M. luteus oxidizes carbohydrates to CO2 and water, and it does not produce acid from glucose as well as it does not make arginine dihydrolase or b-galactosidase. Some Micrococcus are pigmented bacteria; for example, M. luteus produces yellow colonies and M. roseus produces redish colonies. Micrococcus species are oxidase-positive, which can be used to distinguish them from other bacteria like most Staphylococcus species, which are generally oxidase-negative.Micrococcus species can also be differentiated from staphylococcus species by the Taxo A Bacitracin disk test +
Mycobacteria are rod-shaped, Gram-positive aerobes, or facultative anaerobes. As deduced from its genome, M. tuberculosis has the potential to manufacture all of the machinery necessary to synthesize all of its essential vitamins, amino acids, and enzyme co-factors. On the other hand, the inability to culture M. leprae, suggests that it has lost many of its metabolic capabilities, and is now an obligate parasite, dependent on its host for most of its nutritional needs. This goes in accordance with its severely degenerated genome. M. tuberculosis has an unusual cell wall, with an additional layer beyond the peptodiglycan layer, which is rich in unusual lipids, glycolipids, and polysaccharides. +
S
Streptomycetes resemble fungi in their structure. Their branching, filamentous arrangement of cells form a network called a mycelium. They are able to metabolize many different compounds including sugars, alcohols, amino acids, and aromatic compounds by producing extracellular hydrolytic enzymes. Their metabolic diversity is due to their extremely large genome which has hundreds of transcription factors that control gene expression, allowing them to respond to specific needs. +
