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Citrobacter Rodentium
''Citrobacter rodentium'' is a Gram-negative species of bacteria first described in 1996. It infects the intestinal tract of rodents. Cell morphology and features ''C. rodentium'' is an extracellular pathogen of rodents. While its specific structure has not been characterized in detail, several characteristics of this species can be inferred by its classification. As a member of the ''Enterobacteriaceae'' family, it is Gram-negative, rod-shaped, and non-spore-forming. ''C. rodentium'' contains a conserved pathogenicity island in its genome, the locus of enterocyte effacement (LEE). The LEE encodes a type III secretion system which is critical to the infection and pathogenicity of ''C. rodentium''. Only one virulence factor has been identified that is specific to ''C. rodentium'': ''cfc'' (Colonization factor ''Citrobacter''). ''cfc'' encodes the CFC type IV pilus, which has an unknown role, but may be related to multiple aspects of pathogenicity. An analysis of the ''C. rode ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gram Stain
Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. It may also be used to diagnose a fungal infection. The name comes from the Danish bacteriologist Hans Christian Gram, who developed the technique in 1884. Gram staining differentiates bacteria by the chemical and physical properties of their Cell wall#Bacterial cell walls, cell walls. Gram-positive cells have a thick layer of peptidoglycan in the cell wall that retains the primary stain, crystal violet. Gram-negative cells have a thinner peptidoglycan layer that allows the crystal violet to wash out on addition of ethanol. They are stained pink or red by the counterstain, commonly safranin or fuchsine. Lugol's iodine solution is always added after addition of crystal violet to form a stable complex with crystal violet that strengthens the bonds of the stain with the cell wall. Gram staining is almost al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-motile Bacteria
Non-motile bacteria are bacteria species that lack the ability and structures that would allow them to propel themselves, under their own power, through their environment. When non-motile bacteria are cultured in a stab tube, they only grow along the stab line. If the bacteria are mobile, the line will appear diffuse and extend into the medium. The cell structures that provide the ability for locomotion are the cilia and flagella. Coliform and Streptococci are examples of non-motile bacteria as are ''Klebsiella pneumoniae'', and ''Yersinia pestis''. Motility is one characteristic used in the identification of bacteria and evidence of possessing structures: peritrichous flagella, polar flagella and/or a combination of both. Though the lack of motility might be regarded a disadvantage, some non-motile bacteria possess structures that allow their attachment to eukaryotic cells The eukaryotes ( ) constitute the domain of Eukaryota or Eukarya, organisms whose cells have a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Obligate Anaerobe
Obligate anaerobes are microorganisms killed by normal Atmosphere of Earth, atmospheric concentrations of oxygen (20.95% O2). Oxygen tolerance varies between species, with some species capable of surviving in up to 8% oxygen, while others lose viability in environments with an oxygen concentration greater than 0.5%. Oxygen sensitivity The oxygen sensitivity of obligate anaerobes has been attributed to a combination of factors including oxidative stress and enzyme production. Oxygen can also damage obligate anaerobes in ways not involving oxidative stress. Because molecular Triplet oxygen, oxygen contains two unpaired electrons in the HOMO and LUMO, highest occupied molecular orbital, it is readily reduced to superoxide () and hydrogen peroxide () within cells. A reaction between these two products results in the formation of a free hydroxyl radical (OH.). Superoxide, hydrogen peroxide, and hydroxyl radicals are a class of compounds known as reactive oxygen species (ROS), highly r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intestinal Epithelium
The intestinal epithelium is the single cell layer that forms the luminal surface (lining) of both the small and large intestine (colon) of the gastrointestinal tract. Composed of simple columnar epithelium its main functions are absorption, and secretion. Useful substances are absorbed into the body, and the entry of harmful substances is restricted. Secretions include mucins, and peptides. Absorptive cells in the small intestine are known as enterocytes, and in the colon they are known as colonocytes. The other cell types are the secretory cells – goblet cells, Paneth cells, enteroendocrine cells, and Tuft cells. Paneth cells are absent in the colon. As part of its protective role, the intestinal epithelium forms an important component of the intestinal mucosal barrier. Certain diseases and conditions are caused by functional defects in the intestinal epithelium. On the other hand, various diseases and conditions can lead to its dysfunction which, in turn, can lead t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Malonic Acid
Malonic acid is a dicarboxylic acid with structure CH2(COOH)2. The ionized form of malonic acid, as well as its esters and salts, are known as malonates. For example, diethyl malonate is malonic acid's diethyl ester. The name originates from the Greek word μᾶλον (''malon'') meaning 'apple'. History Malonic acid is a naturally occurring substance found in many fruits and vegetables. There is a suggestion that citrus fruits produced in organic farming contain higher levels of malonic acid than fruits produced in conventional agriculture. Malonic acid was first prepared in 1858 by the French chemist Victor Dessaignes via the oxidation of malic acid. Hermann Kolbe and Hugo Müller independently discovered how to synthesize malonic acid from propionic acid, and decided to publish their results back-to-back in the Chemical Society journal in 1864. This led to priority dispute with Hans Hübner and Maxwell Simpson who had independently published preliminary results on rela ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ornithine Decarboxylase
The enzyme ornithine decarboxylase (, ODC) catalyzes the decarboxylation of ornithine (a product of the urea cycle) to form putrescine. This reaction is the committed step in polyamine synthesis. In humans, this protein has 461 amino acids and forms a homodimer. In humans, ornithine decarboxylase (ODC) is expressed by the gene ''ODC1''. The protein ODC is sometimes referred to as "ODC1" in research pertaining to humans and mice, but certain species such as ''Drosophila'' (''dODC2''), species of Solanaceae plant family (''ODC2''), and the lactic acid bacteria '' Paucilactobacillus wasatchensis'' (''odc2'') have been shown to have a second ODC gene. Reaction mechanism Lysine 69 on ornithine decarboxylase (ODC) binds the cofactor pyridoxal phosphate to form a Schiff base. Ornithine displaces the lysine to form a Schiff base attached to orthonine, which decarboxylates to form a quinoid intermediate. This intermediate rearranges to form a Schiff base attached to putrescine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Melibiose
Melibiose is a reducing disaccharide formed by an α-1,6 linkage between galactose and glucose (D-Gal-(α1→6)-D-Glc). It differs from lactose in the chirality of the carbon where the galactose ring is closed and that the galactose is linked to a different point on the glucose moiety. It can be formed by invertase-mediated hydrolysis of raffinose, which produces melibiose and fructose. Melibiose can be broken down into its component saccharides, glucose and galactose, by the enzyme alpha-galactosidase, such as MEL1 from ''Saccharomyces pastorianus'' (lager yeast). Melibiose cannot be used by ''Saccharomyces cerevisiae ''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungal microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have be ...'' (ale yeast), so this is one test to differentiate between the two yeast species. References {{reflist Disa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sucrose
Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refined from either sugarcane or sugar beet. Sugar mills – typically located in tropical regions near where sugarcane is grown – crush the cane and produce raw sugar which is shipped to other factories for refining into pure sucrose. Sugar beet factories are located in temperate climates where the beet is grown, and process the beets directly into refined sugar. The Sugar refinery, sugar-refining process involves washing the raw sugar crystals before dissolving them into a sugar syrup which is filtered and then passed over carbon to remove any residual colour. The sugar syrup is then concentrated by boiling under a vacuum and crystallized as the final purification process to produce crystals of pure sucrose that are clear, odorless, and sweet. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist Carl Wilhelm Scheele is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777. Hydrogen sulfide is toxic to humans and most other animals by inhibiting cellular respiration in a manner similar to hydrogen cyanide. When it is inhaled or its salts are ingested in high amounts, damage to organs occurs rapidly with symptoms ranging from breathing difficulties to convulsions and death. Despite this, the human body produces small amounts of this sulfide and its mineral salts, and uses it as a signalling molecule. Hydrogen sulfide is often produced from the microbial breakdown of organic matter in the absence of oxygen, such as in swamps and sewers; this process is commonly known as anaerobic digestio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arginine
Arginine is the amino acid with the formula (H2N)(HN)CN(H)(CH2)3CH(NH2)CO2H. The molecule features a guanidinium, guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO2−) and both the amino and guanidino groups are protonated, resulting in a cation. Only the -arginine (symbol Arg or R) enantiomer is found naturally. Arg residues are common components of proteins. It is Genetic code, encoded by the DNA codon table, codons CGU, CGC, CGA, CGG, AGA, and AGG. The guanidine group in arginine is the Precursor (chemistry), precursor for the biosynthesis of nitric oxide. Like all amino acids, it is a white, water-soluble solid. The one-letter symbol R was assigned to arginine for its phonetic similarity. History Arginine was first isolated in 1886 from Lupinus luteus, yellow lupin seedlings by the German chemist Ernst Schulze (chemist), Ernst Schulze and his assistant Ernst Steiger. He named it from the Greek ''árg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arginine Dihydrolase
In enzymology, an arginine deiminase () is an enzyme that catalyzes the chemical reaction :L-arginine + H2O \rightleftharpoons L-citrulline + NH3 Thus, the two substrates of this enzyme are L-arginine and H2O, whereas its two products are L-citrulline and NH3. This enzyme belongs to the family of hydrolases, those acting on carbon-nitrogen bonds other than peptide bonds, specifically in linear amidines. The systematic name of this enzyme class is L-arginine iminohydrolase. Other names in common use include arginine dihydrolase, citrulline iminase, and L-arginine deiminase. This enzyme participates in arginine and proline metabolism. This enzyme is widely expressed in bacteria, including streptococcus and actinomyces. The bacterial arginine deiminase expression could be regulated by various environmental factors. Recently, a new enzyme that catalyzes the chemical reaction :L-arginine + 2H2O \rightleftharpoons L-ornithine + 2NH3 + CO2 was identified in cyanobacteria whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Potassium Cyanide
Potassium cyanide is a compound with the formula KCN. It is a colorless salt, similar in appearance to sugar, that is highly soluble in water. Most KCN is used in gold mining, organic synthesis, and electroplating. Smaller applications include jewellery for chemical gilding and buffing. Potassium cyanide is highly toxic, and a dose of 200 to 300 milligrams will kill nearly any human. The moist solid emits small amounts of hydrogen cyanide due to hydrolysis (reaction with water). Hydrogen cyanide is often described as having an odor resembling that of bitter almonds. The taste of potassium cyanide has been described as acrid and bitter, with a burning sensation similar to lye. Potassium cyanide kills so rapidly its taste hasn't been reliably documented, in 2006 an Indian man named M.P. Prasad committed suicide using potassium cyanide. He was a goldsmith and was aware of the mystery behind its taste. In the suicide note Prasad left, the final words written were that potassium ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
