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DNA Uptake Sequence
Uptake signal sequences (USS) are short DNA sequences preferentially taken up by competent bacteria of the family Pasteurellaceae (''e.g.'', ''Haemophilus influenzae''). Similar sequences, called DNA uptake sequences (DUS), are found in species of the family Neisseriaceae (including ''Neisseria meningitidis'' and ''Neisseria gonorrhoeae''). ''Neisseria meningitidis'' Transformation (genetics), Genetic transformation is the process by which a recipient bacterial cell takes up naked DNA from its environment and integrates this DNA into the recipient's genome by Genetic recombination, recombination. In ''Neisseria meningitidis, N. meningitidis'', DNA transformation requires the presence of short DUS (10-12 mers residing in coding and intergenic regions) of the donor DNA. Specific recognition of DUSs is mediated by a type IV Pilus, pilin. Davidsen et al. reported that in ''N. meningitidis'' DUSs occur at a significantly higher density in genes involved in DNA repair and Genetic recomb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, 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 biosphere of Earth's crust. Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of dead bodies; bacteria are responsible for the putrefaction stage in this process. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. Bacteria also live in symbiotic and parasitic relationsh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pasteurellaceae
The Pasteurellaceae comprise a large family of Gram-negative bacteria. Most members live as commensals on mucosal surfaces of birds and mammals, especially in the upper respiratory tract. Pasteurellaceae are typically rod-shaped, and are a notable group of facultative anaerobes. Their biochemical characteristics can be distinguished from the related Enterobacteriaceae by the presence of oxidase, and from most other similar bacteria by the absence of flagella. Bacteria in the family Pasteurellaceae have been classified into a number of genera based on metabolic properties, but these classifications are not generally accurate reflections of the evolutionary relationships between different species. ''Haemophilus influenzae'' was the first organism to have its genome sequenced and has been studied intensively by genetic and molecular methodologies. The genus ''Haemophilus'' is a notorious human pathogen associated with bacteremia, pneumonia, meningitis and chancroid. Other pathogenic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haemophilus Influenzae
''Haemophilus influenzae'' (formerly called Pfeiffer's bacillus or ''Bacillus influenzae'') is a Gram-negative, non-motile, coccobacillary, facultatively anaerobic, capnophilic pathogenic bacterium of the family Pasteurellaceae. The bacteria are mesophilic and grow best at temperatures between 35 and 37℃. ''H. influenzae'' was first described in 1892 by Richard Pfeiffer during an influenza pandemic when he incorrectly described ''Haemophilus influenzae'' as the causative microbe, which is why the bacteria retain the name "influenza". ''H. influenzae'' is responsible for a wide range of localized and invasive infections, typically in infants and children, including pneumonia, meningitis, or bloodstream infections. Treatment consists of antibiotics, however ''H. influenzae'' is often resistant to the penicillin family but augmentin can be used in mild cases. The recommended form of prevention is a series of the Hib vaccine and boosters, which are most often given under the ag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neisseriaceae
The Neisseriaceae are a family of Pseudomonadota, within the ''Neisseriales'' order. While many organisms in the family are mammalian commensals or part of the normal flora, the genus ''Neisseria'' includes two important human pathogens, specifically those responsible for gonorrhea (caused by'' N. gonorrhoeae'') and many cases of meningitis ("meningococcal meningitis", caused by'' N. meningitidis''). As a group, the Neisseriaceae are strictly aerobic and Gram-negative, occur mainly in pairs (diplococci A diplococcus (plural diplococci) is a round bacterium (a coccus) that typically occurs in the form of two joined cells. Types Examples of gram-negative diplococci are '' Neisseria spp.'' and ''Moraxella catarrhalis.'' Examples of gram-posit ...), and typically do not have flagella. References Bacteria of Medical Importancein ''Todar's Online Textbook of Bacteriology''. * * Betaproteobacteria {{Betaproteobacteria-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neisseria Meningitidis
''Neisseria meningitidis'', often referred to as meningococcus, is a Gram-negative bacterium that can cause meningitis and other forms of meningococcal disease such as meningococcemia, a life-threatening sepsis. The bacterium is referred to as a coccus because it is round, and more specifically a diplococcus because of its tendency to form pairs. About 10% of adults are carriers of the bacteria in their nasopharynx. As an exclusively human pathogen, it is the main cause of bacterial meningitis in children and young adults, causing developmental impairment and death in about 10% of cases. It causes the only form of bacterial meningitis known to occur epidemically, mainly in Africa and Asia. It occurs worldwide in both epidemic and endemic form. ''N. meningitidis'' is spread through saliva and respiratory secretions during coughing, sneezing, kissing, chewing on toys and through sharing a source of fresh water. It has also been reported to be transmitted through oral sex and cause ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neisseria Gonorrhoeae
''Neisseria gonorrhoeae'', also known as ''gonococcus'' (singular), or ''gonococci'' (plural), is a species of Gram-negative diplococci bacteria isolated by Albert Ludwig Sigesmund Neisser, Albert Neisser in 1879. It causes the sexually transmitted infection, sexually transmitted genitourinary infection gonorrhea as well as other forms of gonococcal disease including disseminated gonococcemia, septic arthritis, and gonococcal ophthalmia neonatorum. It is oxidase test, oxidase positive and aerobic, and it survives phagocyte, phagocytosis and grows inside neutrophils. Microbiological culture, Culturing it requires carbon dioxide supplementation and enriched agar (chocolate agar) with various antibiotics (Thayer–Martin agar, Thayer–Martin). It exhibits antigenic variation through genetic recombination of its pilus, pili and surface proteins that interact with the immune system. Sexual transmission is through vaginal, anal, or oral sex. Sexual transmission may be prevented throu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transformation (genetics)
In molecular biology and genetics, transformation is the genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material from its surroundings through the cell membrane(s). For transformation to take place, the recipient bacterium must be in a state of competence, which might occur in nature as a time-limited response to environmental conditions such as starvation and cell density, and may also be induced in a laboratory. Transformation is one of three processes that lead to horizontal gene transfer, in which exogenous genetic material passes from one bacterium to another, the other two being conjugation (transfer of genetic material between two bacterial cells in direct contact) and transduction (injection of foreign DNA by a bacteriophage virus into the host bacterium). In transformation, the genetic material passes through the intervening medium, and uptake is completely dependent on the recipient bacterium. As of 2014 about 8 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Recombination
Genetic recombination (also known as genetic reshuffling) is the exchange of genetic material between different organisms which leads to production of offspring with combinations of traits that differ from those found in either parent. In eukaryotes, genetic recombination during meiosis can lead to a novel set of genetic information that can be further passed on from parents to offspring. Most recombination occurs naturally and can be classified into two types: (1) ''interchromosomal'' recombination, occurring through independent assortment of alleles whose loci are on different but homologous chromosomes (random orientation of pairs of homologous chromosomes in meiosis I); & (2) ''intrachromosomal'' recombination, occurring through crossing over. During meiosis in eukaryotes, genetic recombination involves the pairing of homologous chromosomes. This may be followed by information transfer between the chromosomes. The information transfer may occur without physical exchange (a se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pilus
A pilus (Latin for 'hair'; plural: ''pili'') is a hair-like appendage found on the surface of many bacteria and archaea. The terms ''pilus'' and '' fimbria'' (Latin for 'fringe'; plural: ''fimbriae'') can be used interchangeably, although some researchers reserve the term ''pilus'' for the appendage required for bacterial conjugation. All conjugative pili are primarily composed of pilin – fibrous proteins, which are oligomeric. Dozens of these structures can exist on the bacterial and archaeal surface. Some bacteria, viruses or bacteriophages attach to receptors on pili at the start of their reproductive cycle. Pili are antigenic. They are also fragile and constantly replaced, sometimes with pili of different composition, resulting in altered antigenicity. Specific host responses to old pili structures are not effective on the new structure. Recombination genes of pili code for variable (V) and constant (C) regions of the pili (similar to immunoglobulin diversity). As the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Repair
DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA damage, resulting in tens of thousands of individual molecular lesions per cell per day. Many of these lesions cause structural damage to the DNA molecule and can alter or eliminate the cell's ability to transcribe the gene that the affected DNA encodes. Other lesions induce potentially harmful mutations in the cell's genome, which affect the survival of its daughter cells after it undergoes mitosis. As a consequence, the DNA repair process is constantly active as it responds to damage in the DNA structure. When normal repair processes fail, and when cellular apoptosis does not occur, irreparable DNA damage may occur, including double-strand breaks and DNA crosslinkages (interstrand crosslinks or ICLs). This can eventually lead to malignant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genotoxic
Genotoxicity is the property of chemical agents that damage the genetic information within a cell causing mutations, which may lead to cancer. While genotoxicity is often confused with Mutagen, mutagenicity, all mutagens are genotoxic, but some genotoxic substances are not mutagenic. The alteration can have direct or indirect effects on the DNA: the induction of mutations, mistimed event activation, and direct DNA damage leading to mutations. The permanent, heritable changes can affect either somatic cells of the organism or germ cells to be passed on to future generations. Cells prevent expression of the genotoxic mutation by either DNA repair or apoptosis; however, the damage may not always be fixed leading to mutagenesis. To bioassay, assay for genotoxic molecules, researchers assay for DNA damage in cells exposed to the toxic substrates. This DNA damage can be in the form of single- and double-strand breaks, loss of excision repair, cross-linking, alkali-labile sites, point mutat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proceedings Of The National Academy Of Sciences Of The United States Of America
''Proceedings of the National Academy of Sciences of the United States of America'' (often abbreviated ''PNAS'' or ''PNAS USA'') is a peer-reviewed multidisciplinary scientific journal. It is the official journal of the National Academy of Sciences, published since 1915, and publishes original research, scientific reviews, commentaries, and letters. According to ''Journal Citation Reports'', the journal has a 2021 impact factor of 12.779. ''PNAS'' is the second most cited scientific journal, with more than 1.9 million cumulative citations from 2008 to 2018. In the mass media, ''PNAS'' has been described variously as "prestigious", "sedate", "renowned" and "high impact". ''PNAS'' is a delayed open access journal, with an embargo period of six months that can be bypassed for an author fee ( hybrid open access). Since September 2017, open access articles are published under a Creative Commons license. Since January 2019, ''PNAS'' has been online-only, although print issues are ava ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
