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Lysogenic Cycle
LYSOGENY, or the LYSOGENIC CYCLE, is one of two cycles of viral reproduction (the lytic cycle being the other). Lysogeny is characterized by integration of the bacteriophage nucleic acid into the host bacterium's genome or formations of a circular replicon in the bacterial cytoplasm. In this condition the bacterium continues to live and reproduce normally. The genetic material of the bacteriophage, called a prophage , can be transmitted to daughter cells at each subsequent cell division, and at later events (such as UV radiation or the presence of certain chemicals) can release it, causing proliferation of new phages via the lytic cycle. Lysogenic cycles can also occur in eukaryotes , although the method of DNA incorporation is not fully understood. The distinction between lysogenic and lytic cycles is that the spread of the viral DNA occurs through the usual prokaryotic reproduction, while the lytic phage is spread through the production of thousands of individual phages capable of surviving and infecting other cells. The key difference between the lytic cycle and the lysogenic cycle is that the lysogenic cycle does not lyse the host cell. Phages that replicate only via the lytic cycle are known as virulent phages while phages that replicate using both lytic and lysogenic cycles are known as temperate phages. In the lysogenic cycle, the phage DNA first integrates into the bacterial chromosome to produce the prophage
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Lytic Cycle
The LYTIC CYCLE (/ˈlɪtɪk/ LIT-ək ), is one of the two cycles of viral reproduction , the other being the lysogenic cycle . The lytic cycle results in the destruction of the infected cell and its membrane. A key difference between the lytic and lysogenic phage cycles is that in the lytic phage, the viral DNA
DNA
exists as a separate molecule within the bacterial cell, and replicates separately from the host bacterial DNA. The location of viral DNA
DNA
in the lysogenic phage cycle is within the host DNA, therefore in both cases the virus/phage replicates using the host DNA
DNA
machinery, but in the lytic phage cycle, the phage is a free floating separate molecule to the host DNA. CONTENTS* 1 Description * 1.1 Penetrating * 1.2 Gene regulation biochemistry * 1.3 Maturation and lysis * 1.3.1 Lytic cycle
Lytic cycle
without lysis * 2 References DESCRIPTIONViruses that only use lvytic cycle are called virulent viruses (in contrast to temperate viruses). The lytic cycle is a six-stage cycle. In the first stage, called "penetration", the virus injects its own nucleic acid into a host cell. In some viruses this genetic material is circular and mimics a bacterial plasmid . The virus hijacks the cell's replication and translation mechanisms, using them to make more viruses
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Bacteriophage
A BACTERIOPHAGE /ˈbækˈtɪər.i.oʊˌfeɪdʒ/ , also known informally as a _PHAGE_ /ˈfeɪdʒ/ , is a virus that infects and replicates within a bacterium . The term is derived from "bacteria" and the Greek : φαγεῖν (_phagein_), "to devour". Bacteriophages are composed of proteins that encapsulate a DNA or RNA genome , and may have relatively simple or elaborate structures. Their genomes may encode as few as four genes, and as many as hundreds of genes . Phages replicate within the bacterium following the injection of their genome into its cytoplasm . Bacteriophages are among the most common and diverse entities in the biosphere . Bacteriophages are ubiquitous viruses, found wherever bacteria exist. It’s estimated there are more than 1031 bacteriophages on the planet, more than every other organism on Earth, including bacteria, combined. Phages are widely distributed in locations populated by bacterial hosts, such as soil or the intestines of animals. One of the densest natural sources for phages and other viruses is sea water, where up to 9×108 virions per milliliter have been found in microbial mats at the surface, and up to 70% of marine bacteria may be infected by phages. They have been used for over 90 years as an alternative to antibiotics in the former Soviet Union and Central Europe, as well as in France
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Replicon (genetics)
A REPLICON is a DNA
DNA
molecule or RNA
RNA
molecule, or a region of DNA
DNA
or RNA, that replicates from a single origin of replication . CONTENTS * 1 Prokaryotes * 2 Eukaryotes * 3 See also * 4 References PROKARYOTESFor most prokaryotic chromosomes , the replicon is the entire chromosome. One notable exception found comes from archaea , where two Sulfolobus species have been shown to contain three replicons. Examples of bacterial species that have been found to possess multiple replicons include: Rhodobacter sphaeroides (2), Vibrio cholerae
Vibrio cholerae
, and Burkholderia multivorans (3). These "secondary" (or tertiary) chromosomes are often described as a molecule that is a mixture between a true chromosome and a plasmid and are sometimes called "chromids". Various Azospirillum species possess 7 replicons, Azospirillum lipoferum , for instance, has 1 bacterial chromosome, 5 chromids, and 1 plasmid. Plasmids and bacteriophages are usually replicated as single replicons, but large plasmids in Gram-negative bacteria have been shown to carry several replicons. EUKARYOTESFor eukaryotic chromosomes, there are multiple replicons per chromosome. In the case of mitochondria the definition of replicons is somewhat confused, as they use unidirectional replication with two separate origins
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Prophage
A PROPHAGE is a bacteriophage (often shortened to "phage") genome inserted and integrated into the circular bacterial DNA chromosome or existing as an extrachromosomal plasmid . This is a latent form of a phage, in which the viral genes are present in the bacterium without causing disruption of the bacterial cell . Pro means ''before'', so, prophage means the stage of a virus in the form of genome inserted into host DNA before attaining its real form inside host. CONTENTS * 1 Prophage
Prophage
induction * 2 Zygotic induction * 3 References * 4 See also PROPHAGE INDUCTIONUpon detection of host cell damage, such as UV light or certain chemicals, the prophage is excised from the bacterial chromosome in a process called prophage induction. After induction, viral replication begins via the Lytic Cycle . In the lytic cycle, the virus commandeers the cell's reproductive machinery. The cell may fill with new viruses until it lyses or bursts, or it may release the new viruses one at a time in a reverse endocytotic process. The period from infection to lysis is termed the latent period. A virus following a lytic cycle is called a virulent virus. Prophages are important agents of horizontal gene transfer , and are considered part of the mobilome
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Ultraviolet
ULTRAVIOLET (UV) is an electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays . UV radiation constitutes about 10% of the total light output of the Sun, and is thus present in sunlight . It is also produced by electric arcs and specialized lights, such as mercury-vapor lamps , tanning lamps , and black lights . Although it is not considered an ionizing radiation because its photons lack the energy to ionize atoms , long-wavelength ultraviolet radiation can cause chemical reactions and causes many substances to glow or fluoresce . Consequently, the biological effects of UV are greater than simple heating effects, and many practical applications of UV radiation derive from its interactions with organic molecules. Suntan , freckling and sunburn are familiar effects of over-exposure, along with higher risk of skin cancer . Living things on dry land would be severely damaged by ultraviolet radiation from the Sun
Sun
if most of it were not filtered out by the Earth's atmosphere. More-energetic, shorter-wavelength "extreme" UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground. Ultraviolet
Ultraviolet
is also responsible for the formation of bone-strengthening vitamin D in most land vertebrates, including humans. The UV spectrum thus has effects both beneficial and harmful to human health
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Eukaryote
Eukaryotic organisms that cannot be classified under the kingdoms Plantae, Animalia or Fungi are sometimes grouped in the kingdom PROTISTA . A EUKARYOTE (/juːˈkæri.oʊt/ or /juːˈkæriət/ ) is any organism whose cells have a cell nucleus and other organelles enclosed within membranes . Eukaryotes belong to the taxon EUKARYA or EUKARYOTA. The defining feature that sets eukaryotic cells apart from prokaryotic cells ( Bacteria and Archaea ) is that they have membrane-bound organelles, especially the nucleus, which contains the genetic material and is enclosed by the nuclear envelope . The presence of a nucleus gives eukaryotes their name, which comes from the Greek εὖ (_eu_, "well" or "true") and κάρυον (_karyon_, "nut" or "kernel"). Eukaryotic cells also contain other membrane-bound organelles such as mitochondria and the Golgi apparatus . In addition, plants and algae contain chloroplasts . Eukaryotic organisms may be unicellular or multicellular . Only eukaryotes form multicellular organisms consisting of many kinds of tissue made up of different cell types . Eukaryotes can reproduce both asexually through mitosis and sexually through meiosis and gamete fusion. In mitosis, one cell divides to produce two genetically identical cells
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Temperateness (virology)
In VIROLOGY , TEMPERATE refers to the ability of some bacteriophages (notably coliphage λ ) to display a lysogenic life cycle . Many (but not all) temperate phages can integrate their genomes into their host bacterium\'s chromosome, together becoming a lysogen as the phage genome becomes a prophage . A temperate phage is also able to undergo a productive, typically lytic life cycle, where the prophage is expressed, replicates the phage genome, and produces phage progeny, which then leave the bacterium . With phage the term virulent is often used as an antonym to temperate, but more strictly a virulent phage is one that has lost its ability to display lysogeny through mutation rather than a phage lineage with no genetic potential to ever display lysogeny (which more properly would be described as an obligately lytic phage). NOTES * ^ Barksdale, L., and S. B. Ardon. 1974. Persisting bacteriophage infections, lysogeny, and phage conversions. Annu. Rev. Microbiol. 28:265-299. This virus -related article is a stub . You can help by expanding it . * v * t * e Retrieved from "https://en.wikipedia.org/w/index.php?title=Temperateness_(virology) additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy .® is a registered trademark of the Wikimedia Foundation, Inc
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Lambda Phage
ENTEROBACTERIA PHAGE λ (LAMBDA PHAGE , COLIPHAGE λ) is a bacterial virus, or bacteriophage , that infects the bacterial species Escherichia coli
Escherichia coli
(E. coli). It was discovered by Esther Lederberg
Esther Lederberg
in 1950 when she noticed that streaks of mixtures of two E. coli strains, one of which treated with ultraviolet light, was "nibbled and plaqued ". The wild type of this virus has a temperate lifecycle that allows it to either reside within the genome of its host through lysogeny or enter into a lytic phase (during which it kills and lyses the cell to produce offspring); mutant strains are unable to lysogenize cells- instead they grow and enter the lytic cycle after superinfecting an already lysogenized cell. The phage particle consists of a head (also known as a capsid ), a tail, and tail fibers (see image of virus below). The head contains the phage's double-strand linear DNA
DNA
genome. During infection, the phage particle recognizes and binds to its host, E. coli, causing DNA in the head of the phage to be ejected through the tail into the cytoplasm of the bacterial cell. Usually, a "lytic cycle " ensues, where the lambda DNA
DNA
is replicated and new phage particles are produced within the cell. This is followed by cell lysis , releasing the cell contents, including virions that have been assembled, into the environment
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Lysogens
A LYSOGEN or LYSOGENIC BACTERIUM is a bacterial cell in which a phage exists as DNA in its dormant state (prophage ). A prophage is either integrated into the host bacteria 's chromosome or more rarely exists as a stable plasmid within the host cell. The prophage expresses gene(s) that repress the phage's lytic action, until this repression is disrupted (see lytic cycle ). Currently a variety of studies are being conducted to see whether other genes are active during lysogeny, examples of which include phage-encoded tRNA and virulence genes. TYPES * lambda phage SEE ALSO * lysogenic cycle Retrieved from "https://en.wikipedia.org/w/index.php?title= Lysogen additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy .® is a registered trademark of the Wikimedia Foundation, Inc
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Phenotype
A PHENOTYPE (from Greek _phainein_, meaning 'to show', and _typos_, meaning 'type') is the composite of an organism 's observable characteristics or traits , such as its morphology , development , biochemical or physiological properties, behavior , and products of behavior (such as a bird's nest). A phenotype results from the expression of an organism's genetic code, its genotype , as well as the influence of environmental factors and the interactions between the two. When two or more clearly different phenotypes exist in the same population of a species, the species is called polymorphic . A well-documented polymorphism is Labrador Retriever coloring ; while the coat color depends on many genes, it is clearly seen in the environment as yellow, black and brown. This genotype-phenotype distinction was proposed by Wilhelm Johannsen in 1911 to make clear the difference between an organism's heredity and what that heredity produces. The distinction is similar to that proposed by August Weismann , who distinguished between germ plasm (heredity) and somatic cells (the body). The genotype-phenotype distinction should not be confused with Francis Crick 's central dogma of molecular biology , which is a statement about the directionality of molecular sequential information flowing from DNA to protein, and not the reverse
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Bacteria
Actinobacteria (high-G+C ) Firmicutes (low-G+C ) Tenericutes (no wall ) * GRAM NEGATIVE / OUTER MEMBRANE PRESENT Aquificae Bacteroidetes / Fibrobacteres Chlorobi ( FCB group ) Chlamydiae Deinococcus-Thermus Fusobacteria Gemmatimonadetes Nitrospirae Planctomycetes Verrucomicrobia / Chlamydiae ( PVC group ) Proteobacteria Spirochaetes Synergistetes * UNKNOWN / UNGROUPED Acidobacteria Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Dictyoglomi Thermodesulfobacteria Thermotogae SYNONYMS Eubacteria Woese common noun BACTERIA, singular BACTERIUM) constitute a large domain of prokaryotic microorganisms . Typically a few micrometres in length, bacteria have a number of shapes , ranging from spheres to rods and spirals . Bacteria were among the first life forms to appear on Earth , and are present in most of its habitats . Bacteria inhabit soil, water, acidic hot springs , radioactive waste , and the deep portions of Earth\'s crust . Bacteria also live in symbiotic and parasitic relationships with plants and animals
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Virulence Factor
VIRULENCE FACTORS are molecules produced by bacteria , viruses , fungi , and protozoa that add to their effectiveness and enable them to achieve the following: * colonization of a niche in the host (this includes attachment to cells) * immunoevasion, evasion of the host's immune response * immunosuppression , inhibition of the host's immune response * entry into and exit out of cells (if the pathogen is an intracellular one) * obtain nutrition from the hostSpecific pathogens possess a wide array of virulence factors. Some are chromosomally encoded and intrinsic to the bacteria (e.g. capsules and endotoxin ), whereas others are obtained from mobile genetic elements like plasmids and bacteriophages (e.g. some exotoxins). Virulence
Virulence
factors encoded on mobile genetic elements spread through horizontal gene transfer , and can convert harmless bacteria into dangerous pathogens. Bacteria
Bacteria
like Escherichia coli O157:H7 gain the majority of their virulence from mobile genetic elements. Gram-negative bacteria
Gram-negative bacteria
secrete a variety of virulence factors at host-pathogen interface , via membrane vesicle trafficking as bacterial outer membrane vesicles for invasion, nutrition and other cell-cell communications. It has been found that many pathogens have converged on similar virulence factors to battle against eukaryotic host defenses
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Biofilm
Note 1: A biofilm is a system that can be adapted internally to environmental conditions by its inhabitants. Note 2: The self-produced matrix of extracellular polymeric substances , which is also referred to as slime, is a polymeric conglomeration generally composed of extracellular biopolymers in various structural forms. A BIOFILM is any group of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular polymeric substances (EPS). The EPS components are produced by the cells within the biofilm and are typically a polymeric conglomeration of extracellular DNA
DNA
, proteins , and polysaccharides . Because they have three-dimensional structure and represent a community lifestyle for microorganisms, biofilms are frequently described metaphorically as "cities for microbes." Biofilms may form on living or non-living surfaces and can be prevalent in natural, industrial and hospital settings. The microbial cells growing in a biofilm are physiologically distinct from planktonic cells of the same organism, which, by contrast, are single-cells that may float or swim in a liquid medium. Biofilms can be present on the teeth of most animals as dental plaque , where they may cause tooth decay and gum disease
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Bacillus Anthracis
BACILLUS ANTHRACIS is the etiologic agent of anthrax —a common disease of livestock and, occasionally, of humans—and the only obligate pathogen within the genus Bacillus . B. anthracis is a Gram-positive , endospore -forming, rod-shaped bacterium , with a width of 1.0–1.2 µm and a length of 3–5 µm. It can be grown in an ordinary nutrient medium under aerobic or anaerobic conditions. B. anthracis belongs to the B. cereus group of strains. Structure of B. anthracis It is one of few bacteria known to synthesize a protein capsule (poly-D-gamma-glutamic acid). Like Bordetella pertussis , it forms a calmodulin -dependent adenylate cyclase exotoxin known as Anthrax edema factor , along with anthrax lethal factor . It bears close genotypical and phenotypical resemblance to Bacillus cereus and Bacillus thuringiensis . All three species share cellular dimensions and morphology . All form oval spores located centrally in an unswollen sporangium . B. anthracis endospores, in particular, are highly resilient, surviving extremes of temperature, low-nutrient environments, and harsh chemical treatment over decades or centuries. The endospore is a dehydrated cell with thick walls and additional layers that form inside the cell membrane. It can remain inactive for many years, but if it comes into a favorable environment, it begins to grow again. It initially develops inside the rod-shaped form
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Bacillus Subtilis
_BACILLUS SUBTILIS_, known also as the HAY BACILLUS or GRASS BACILLUS, is a Gram-positive , catalase -positive bacterium , found in soil and the gastrointestinal tract of ruminants and humans. A member of the genus _ Bacillus _, _B. subtilis_ is rod-shaped, and can form a tough, protective endospore , allowing it to tolerate extreme environmental conditions. _B. subtilis_ has historically been classified as an obligate aerobe , though evidence exists that it is a facultative aerobe . _B. subtilis_ is considered the best studied Gram-positive bacterium and a model organism to study bacterial chromosome replication and cell differentiation. It is one of the bacterial champions in secreted enzyme production and used on an industrial scale by biotechnology companies. CONTENTS * 1 Description * 2 Habitat * 3 Reproduction * 4 Chromosomal replication * 5 Genome * 6 Transformation * 7 Uses * 7.1 1900s * 7.2 2000s * 8 Safety * 8.1 In animals * 8.2 In humans * 9 Identification * 10 See also * 11 References * 12 External links DESCRIPTION_ Bacillus subtilis_ is a Gram-positive bacterium, rod-shaped and catalase -positive. It was originally named _Vibrio subtilis_ by Christian Gottfried Ehrenberg , and renamed _ Bacillus subtilis_ by Ferdinand Cohn in 1872 (subtilis being the Latin for 'fine')
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