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Tyrothricin
Tyrothricin is an antibiotic mixture which was isolated from '' Bacillus brevis'' by Rene Dubos in the late 1930s. It was later shown by Dubos and Rollin Hotchkiss to be a mixture of two different antibiotics: gramicidin and tyrocidine. Both gramicidin and tyrocidine are short polypeptides which disrupt the cell membranes of some, primarily Gram-positive, bacteria. Tyrothricin and its component antibiotics are too toxic to be taken internally but are sometimes used as topical antibiotics. Tyrothricin, and its component antibiotics, belongs to the pharmacologically related group of polypeptide antibiotic compounds including colistin, polymyxin B, and bacitracin Bacitracin is a polypeptide antibiotic. It is a mixture of related cyclic peptides produced by ''Bacillus licheniformis'' bacteria, that was first isolated from the variety "Tracy I" ( ATCC 10716) in 1945. These peptides disrupt Gram-positive bac .... There is no cross-resistance to these three agents. References ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tyrocidine
Tyrocidine is a mixture of cyclic decapeptides produced by the bacteria ''Bacillus brevis'' found in soil. It can be composed of 4 different amino acid sequences, giving tyrocidine A–D (See figure 1). Tyrocidine is the major constituent of tyrothricin, which also contains gramicidin.Pubchem: Tyrocidine and Tyrothricin. Tyrocidine was the first commercially available antibiotic, but has been found to be toxic toward human blood and reproductive cells. The function of tyrocidine within its host ''B. brevis'' is thought to be regulation of sporulation. Tyrocidines A, B, and C are cyclic decapeptides. The biosynthesis of tyrocidine involves three enzymes. Parts of its sequence are identical to gramicidin S. History In 1939, the American microbiologist René Dubos discovered the soil microbe ''Bacillus brevis''. He observed the ability of the microbe to decompose the capsule of pneumococcus bacterium, rendering it harmless. From the soil microbe ''B. brevis'', he isolated t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antibiotic
An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention of such infections. They may either kill or inhibit the growth of bacteria. A limited number of antibiotics also possess antiprotozoal activity. Antibiotics are not effective against viruses such as the common cold or influenza; drugs which inhibit viruses are termed antiviral drugs or antivirals rather than antibiotics. Sometimes, the term ''antibiotic''—literally "opposing life", from the Greek roots ἀντι ''anti'', "against" and βίος ''bios'', "life"—is broadly used to refer to any substance used against microbes, but in the usual medical usage, antibiotics (such as penicillin) are those produced naturally (by one microorganism fighting another), whereas non-antibiotic antibacterials (such as sulfonamides and antise ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gramicidin
Gramicidin, also called gramicidin D, is a mix of ionophoric antibiotics, gramicidin A, B and C, which make up about 80%, 5%, and 15% of the mix, respectively. Each has 2 isoforms, so the mix has 6 different types of gramicidin molecules. They can be extracted from ''Brevibacillus brevis'' soil bacteria. Gramicidins are linear peptides with 15 amino acids. This is in contrast to unrelated gramicidin S, which is a cyclic peptide. Medical uses Gramicidins work as antibiotics against gram-positive bacteria like ''Bacillus subtilis'' and ''Staphylococcus aureus'', but not well against gram-negative ones like '' E. coli''. Gramicidins are used in medicinal lozenges for sore throat and in topical medicines to treat infected wounds. Gramicidins are often mixed with other antibiotics like tyrocidine and antiseptics. Gramicidins are also used in eye drops for bacterial eye infections. In drops, they are often mixed with other antibiotics like polymyxin B or neomycin. Multiple antibiotic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacillus Brevis
''Brevibacillus brevis'' (formerly known as ''Bacillus brevis'') is a Gram-positive, aerobic, motile, spore-forming, rod-shaped bacterium commonly found in soil, air, water, and decaying matter. It is rarely associated with infectious diseases. The antibiotics gramicidin and tyrocidine were first isolated from it.Abedon, Stephen. "Bacteria Binomials." 26 Apr 1998. Ohio State University. 17 Jun 2006 . ''Brevibacillus brevis'' is catalase positive, amylase negative, casein negative, gelatinase positive, and indole negative; most strains are citrate users. Some strains are capable of oxidizing carbon monoxide Carbon monoxide ( chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simpl ... aerobically. Optimal growth occurs at 35 °C to 55 °C. References Paenibacillaceae Bacteria described i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rollin Hotchkiss
Rollin Douglas Hotchkiss (1911 – December 12, 2004) was an American biochemist who helped to establish the role of DNA as the genetic material and contributed to the isolation and purification of the first antibiotics. His work on bacterial transformation helped lay the groundwork for the field of molecular genetics.Philip Siekevitz,In Memory of Rollin Hotchkiss, '' ASBC Newsletter'', February 2005. Education Hotchkiss was born in South Britain, Connecticut. The son of factory workers, he attended Yale University after scoring the highest in the nation on an achievement test. Hotchkiss earned a B.S. in chemistry in 1932, and remained at Yale for a Ph.D. in organic chemistry. After completing his doctoral work in 1935, Hotchkiss became a fellow of the Rockefeller Institute of Medical Research, where he would remain until retirement in 1982. Research career At the Rockefeller Institute, Hotchkiss initially worked as an assistant to Oswald Avery and Walter Goebel, and was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polypeptides
Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A polypeptide is a longer, continuous, unbranched peptide chain. Hence, peptides fall under the broad chemical classes of biological polymers and oligomers, alongside nucleic acids, oligosaccharides, polysaccharides, and others. A polypeptide that contains more than approximately 50 amino acids is known as a protein. Proteins consist of one or more polypeptides arranged in a biologically functional way, often bound to ligands such as coenzymes and cofactors, or to another protein or other macromolecule such as DNA or RNA, or to complex macromolecular assemblies. Amino acids that have been incorporated into peptides are termed residues. A water molecule is released during formation of each amide bond.. All peptides except cyclic peptide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Membranes
The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (the extracellular space). The cell membrane consists of a lipid bilayer, made up of two layers of phospholipids with cholesterols (a lipid component) interspersed between them, maintaining appropriate membrane fluidity at various temperatures. The membrane also contains membrane proteins, including integral proteins that span the membrane and serve as membrane transporters, and peripheral proteins that loosely attach to the outer (peripheral) side of the cell membrane, acting as enzymes to facilitate interaction with the cell's environment. Glycolipids embedded in the outer lipid layer serve a similar purpose. The cell membrane controls the movement of substances in and out of cells and organelles, being selectively permeable to i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gram-positive Bacteria
In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bacteria take up the crystal violet stain used in the test, and then appear to be purple-coloured when seen through an optical microscope. This is because the thick peptidoglycan layer in the bacterial cell wall retains the stain after it is washed away from the rest of the sample, in the decolorization stage of the test. Conversely, gram-negative bacteria cannot retain the violet stain after the decolorization step; alcohol used in this stage degrades the outer membrane of gram-negative cells, making the cell wall more porous and incapable of retaining the crystal violet stain. Their peptidoglycan layer is much thinner and sandwiched between an inner cell membrane and a bacterial outer membrane, causing them to take up the counterstain ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Colistin
Colistin, also known as polymyxin E, is an antibiotic medication used as a last-resort treatment for multidrug-resistant Gram-negative infections including pneumonia. These may involve bacteria such as ''Pseudomonas aeruginosa'', '' Klebsiella pneumoniae'', or '' Acinetobacter''. It comes in two forms: colistimethate sodium can be injected into a vein, injected into a muscle, or inhaled, and colistin sulfate is mainly applied to the skin or taken by mouth. Colistimethate sodium is a prodrug; it is produced by the reaction of colistin with formaldehyde and sodium bisulfite, which leads to the addition of a sulfomethyl group to the primary amines of colistin. Colistimethate sodium is less toxic than colistin when administered parenterally. In aqueous solutions it undergoes hydrolysis to form a complex mixture of partially sulfomethylated derivatives, as well as colistin. Resistance to colistin began to appear as of 2015. Common side effects of the injectable form include ki ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymyxin B
Polymyxin B, sold under the brand name Poly-Rx among others, is an antibiotic used to treat meningitis, pneumonia, sepsis, and urinary tract infections. While it is useful for many Gram negative infections, it is not useful for Gram positive infections. It can be given by injection into a vein, muscle, or cerebrospinal fluid or inhaled. The injectable form is generally only used if other options are not available. It is also available as the combinations bacitracin/polymyxin B and neomycin/polymyxin B/bacitracin for use on the skin. Common side effects when given by injection include kidney problems, neurological problems, fever, itchiness, and rash. Injections into muscle may result in significant pain. Other serious side effects may include fungal infections, anaphylaxis, and muscle weakness. It is unclear if use during pregnancy is safe for the baby. Polymyxin B works by breaking down the cytoplasmic membrane which generally results in bacterial cell death. Polymyxin B ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacitracin
Bacitracin is a polypeptide antibiotic. It is a mixture of related cyclic peptides produced by ''Bacillus licheniformis'' bacteria, that was first isolated from the variety "Tracy I" ( ATCC 10716) in 1945. These peptides disrupt Gram-positive bacteria by interfering with cell wall and peptidoglycan synthesis. Bacitracin is primarily used as a topical preparation, as it can cause kidney damage when used internally. It is generally safe when used topically, but in rare cases may cause hypersensitivity, allergic or anaphylactic reactions, especially in patient allergic to neomycin. Medical uses Bacitracin is used in human medicine as a polypeptide antibiotic and is "approved by the U.S. Food and Drug Administration (FDA) for use in chickens and turkeys," though use in animals contributes to antibiotic resistance. As bacitracin zinc salt, in combination with other topical antibiotics (usually polymyxin B and neomycin) as an ointment ("triple antibiotic ointment," with the brand ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
