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Bacteriocins
Bacteriocins are proteinaceous or peptidic toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strain(s). They are similar to yeast and paramecium killing factors, and are structurally, functionally, and ecologically diverse. Applications of bacteriocins are being tested to assess their application as narrow-spectrum antibiotics. Bacteriocins were first discovered by André Gratia in 1925. He was involved in the process of searching for ways to kill bacteria, which also resulted in the development of antibiotics and the discovery of bacteriophage, all within a span of a few years. He called his first discovery a ''colicine'' because it killed ''E. coli.'' Classification Bacteriocins are categorized in several ways, including producing strain, common resistance mechanisms, and mechanism of killing. There are several large categories of bacteriocin which are only phenomenologically related. These include the bacteriocins from gram-posit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Class II Bacteriocins
Class II bacteriocins are a class of small peptides that inhibit the growth of various bacteria. Many Gram-positive bacteria produce ribosomally synthesized antimicrobial peptides, termed bacteriocins. Bacteriocins for which disulfide bonds are the only modification to the peptide are Class II bacteriocins. Class IIa One important and well studied class of bacteriocins is the class IIa or pediocin-like bacteriocins produced by lactic acid bacteria. All class IIa bacteriocins are produced by food-associated strains, isolated from a variety of food products of industrial and natural origins, including meat products, dairy products and vegetables. Class IIa bacteriocins are all cationic, display anti-''Listeria'' activity, and kill target cells by permeabilizing the cell membrane. Class IIa bacteriocins contain between 37 and 48 residues. Based on their primary structures, the peptide chains of class IIa bacteriocins may be divided roughly into two regions: a hydrophilic, cationi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lantibiotic
Lantibiotics are a class of polycyclic peptide antibiotics that contain the characteristic thioether amino acids lanthionine or methyllanthionine, as well as the unsaturated amino acids dehydroalanine, and 2-aminoisobutyric acid. They belong to ribosomally synthesized and post-translationally modified peptides. Lanthionine is composed of two alanine residues that are crosslinked on their β-carbon atoms by a thioether (monosulfide) linkage. Lantibiotics are produced by a large number of Gram-positive bacteria such as ''Streptococcus'' and ''Streptomyces'' to attack other Gram-positive bacteria, and as such, they are considered a member of the bacteriocins. Bacteriocins are classified according to their extent of posttranslational modification. The lantibiotics are a class of more extensively modified bacteriocins, also called Class I bacteriocins. (Bacteriocins for which disulfide bonds are the only modification to the peptide are Class II bacteriocins.) Lantibiotics are we ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nisin
Nisin is a polycyclic antibacterial peptide produced by the bacterium '' Lactococcus lactis'' that is used as a food preservative. It has 34 amino acid residues, including the uncommon amino acids lanthionine (Lan), methyllanthionine (MeLan), didehydroalanine (Dha), and didehydroaminobutyric acid (Dhb). These unusual amino acids are introduced by posttranslational modification of the precursor peptide. In these reactions a ribosomally synthesized 57-mer is converted to the final peptide. The unsaturated amino acids originate from serine and threonine, and the enzyme-catalysed addition of cysteine residues to the didehydro amino acids result in the multiple (5) thioether bridges. Subtilin and epidermin are related to nisin. All are members of a class of molecules known as lantibiotics. In the food industry, nisin is obtained from the culturing of ''L. lactis'' on natural substrates, such as milk or dextrose, and it is not chemically synthesized. It was originally isolated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lantibiotics
Lantibiotics are a class of polycyclic peptide antibiotics that contain the characteristic thioether amino acids lanthionine or methyllanthionine, as well as the unsaturated amino acids dehydroalanine, and 2-aminoisobutyric acid. They belong to ribosomally synthesized and post-translationally modified peptides. Lanthionine is composed of two alanine residues that are crosslinked on their β-carbon atoms by a thioether (monosulfide) linkage. Lantibiotics are produced by a large number of Gram-positive bacteria such as '' Streptococcus'' and ''Streptomyces'' to attack other Gram-positive bacteria, and as such, they are considered a member of the bacteriocins. Bacteriocins are classified according to their extent of posttranslational modification. The lantibiotics are a class of more extensively modified bacteriocins, also called Class I bacteriocins. (Bacteriocins for which disulfide bonds are the only modification to the peptide are Class II bacteriocins.) Lantibiotics a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyocin
Pyocins are bacteriocins produced by bacteria belonging to the ''Pseudomonas'' genus. François Jacob François Jacob (17 June 1920 – 19 April 2013) was a French biologist who, together with Jacques Monod, originated the idea that control of enzyme levels in all cells occurs through regulation of transcription. He shared the 1965 Nobel Prize ... described the first pyocin in 1954. Pyocins can be divided into three distinct classes: S-type, R-type, and F-type pyocins. S-type pyocins are colicin-like bacteriocins as R-type and F-type pyocins belong to tailocins. S-type pyocins S-type (soluble) pyocins are binary protein complexes that compose of a cytotoxic protein and an immunity protein that protects the producing strain from cytotoxic effects. The amino-terminal domain of the protein takes part in receptor binding as the carboxy-terminal domain is responsible for cytotoxic effect. Most S-type pyocins act by degrading DNA and RNA but some exhibit their cytotoxicity by form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Colicins
A colicin is a type of bacteriocin produced by and toxic to some strains of ''Escherichia coli''. Colicins are released into the environment to reduce competition from other bacterial strains. Colicins bind to outer membrane receptors, using them to translocate to the cytoplasm or cytoplasmic membrane, where they exert their cytotoxic effect, including depolarisation of the cytoplasmic membrane, DNase activity, RNase activity, or inhibition of murein synthesis. Structure Channel-forming colicins (colicins A, B, E1, Ia, Ib, and N) are transmembrane proteins that depolarize the cytoplasmic membrane, leading to dissipation of cellular energy. These colicins contain at least three domains: an N-terminal translocation domain responsible for movement across the outer membrane and periplasmic space; a central domain responsible for receptor recognition; and a C-terminal cytotoxic domain responsible for channel formation in the cytoplasmic membrane. One domain regulates the target an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Colicins
A colicin is a type of bacteriocin produced by and toxic to some strains of ''Escherichia coli''. Colicins are released into the environment to reduce competition from other bacterial strains. Colicins bind to outer membrane receptors, using them to translocate to the cytoplasm or cytoplasmic membrane, where they exert their cytotoxic effect, including depolarisation of the cytoplasmic membrane, DNase activity, RNase activity, or inhibition of murein synthesis. Structure Channel-forming colicins (colicins A, B, E1, Ia, Ib, and N) are transmembrane proteins that depolarize the cytoplasmic membrane, leading to dissipation of cellular energy. These colicins contain at least three domains: an N-terminal translocation domain responsible for movement across the outer membrane and periplasmic space; a central domain responsible for receptor recognition; and a C-terminal cytotoxic domain responsible for channel formation in the cytoplasmic membrane. One domain regulates the target an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific 3D structure that determines its activity. A linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide. Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides. The individual amino acid residues are bonded together by peptide bonds and adjacent amino acid residues. The sequence of amino acid resid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peptidoglycan
Peptidoglycan or murein is a unique large macromolecule, a polysaccharide, consisting of sugars and amino acids that forms a mesh-like peptidoglycan layer outside the plasma membrane, the rigid Cell wall#Bacterial_cell_walls, cell wall (murein sacculus) characteristic of most bacteria (Domain (biology), domain ''Bacteria''). The sugar component consists of alternating residues of β-(1,4) linked N-Acetylglucosamine, ''N''-acetylglucosamine (NAG) and N-Acetylmuramic acid, ''N''-acetylmuramic acid (NAM). Attached to the ''N''-acetylmuramic acid is a oligopeptide chain made of three to five amino acids. The peptide chain can be cross-linked to the peptide chain of another strand forming the 3D mesh-like layer. Peptidoglycan serves a structural role in the bacterial cell wall, giving structural strength, as well as counteracting the osmotic pressure of the cytoplasm. This repetitive linking results in a dense peptidoglycan layer which is critical for maintaining cell form and withstandi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
N-terminus
The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the amine group is bonded to the carboxylic group of another amino acid, making it a chain. That leaves a free carboxylic group at one end of the peptide, called the C-terminus, and a free amine group on the other end called the N-terminus. By convention, peptide sequences are written N-terminus to C-terminus, left to right (in LTR writing systems). This correlates the translation direction to the text direction, because when a protein is translated from messenger RNA, it is created from the N-terminus to the C-terminus, as amino acids are added to the carboxyl end of the protein. Chemistry Each amino acid has an amine group and a carboxylic group. Amino acids link to one another by peptide bonds which form through a dehydration reaction ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudomonas Aeruginosa
''Pseudomonas aeruginosa'' is a common encapsulated, gram-negative, aerobic– facultatively anaerobic, rod-shaped bacterium that can cause disease in plants and animals, including humans. A species of considerable medical importance, ''P. aeruginosa'' is a multidrug resistant pathogen recognized for its ubiquity, its intrinsically advanced antibiotic resistance mechanisms, and its association with serious illnesses – hospital-acquired infections such as ventilator-associated pneumonia and various sepsis syndromes. The organism is considered opportunistic insofar as serious infection often occurs during existing diseases or conditions – most notably cystic fibrosis and traumatic burns. It generally affects the immunocompromised but can also infect the immunocompetent as in hot tub folliculitis. Treatment of ''P. aeruginosa'' infections can be difficult due to its natural resistance to antibiotics. When more advanced antibiotic drug regimens are needed adverse eff ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microcin
Microcins are very small bacteriocins, composed of relatively few amino acids. For this reason, they are distinct from their larger protein cousins. The classic example is microcin V, of ''Escherichia coli''. Subtilosin A is another bacteriocin from ''Bacillus subtilis''. The peptide has a cyclized backbone and forms three cross-links between the sulphurs of Cys13, Cys7 and Cys4 and the alpha-positions of Phe22, Thr28 and Phe31. Microcins produced by commensal ''E. coli'' strains target and eliminate enteric pathogens such as ''Salmonella enterica'' by mimicking the siderophore Siderophores (Greek: "iron carrier") are small, high-affinity iron- chelating compounds that are secreted by microorganisms such as bacteria and fungi. They help the organism accumulate iron. Although a widening range of siderophore functions is n ...s the pathogens use for iron scavenging. Microcins also help commensal strains of ''E. coli'' outcompete pathogenic strains. BACTIBASE database is an op ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
