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Axenic
In biology, axenic (, ) describes the state of a culture in which only a single species, variety, or strain of organism is present and entirely free of all other contaminating organisms. The earliest axenic cultures were of bacteria or unicellular eukaryotes, but axenic cultures of many multicellular organisms are also possible. Axenic culture is an important tool for the study of symbiotic and parasitic organisms in a controlled environment. Preparation Axenic cultures of microorganisms are typically prepared by subculture of an existing mixed culture. This may involve use of a dilution series, in which a culture is successively diluted to the point where subsamples of it contain only a few individual organisms, ideally only a single individual (in the case of an asexual species). These subcultures are allowed to grow until the identity of their constituent organisms can be ascertained. Selection of those cultures consisting solely of the desired organism produces the axenic cu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Agar Plate
An agar plate is a Petri dish that contains a growth medium solidified with agar, used to culture microorganisms. Sometimes selective compounds are added to influence growth, such as antibiotics. Individual microorganisms placed on the plate will grow into individual colonies, each a clone genetically identical to the individual ancestor organism (except for the low, unavoidable rate of mutation). Thus, the plate can be used either to estimate the concentration of organisms in a liquid culture or a suitable dilution of that culture using a colony counter, or to generate genetically pure cultures from a mixed culture of genetically different organisms. Several methods are available to plate out cells. One technique is known as "streaking". In this technique, a drop of the culture on the end of a thin, sterile loop of wire, sometimes known as an inoculator, is streaked across the surface of the agar leaving organisms behind, a higher number at the beginning of the streak and a l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Serial Dilution
A serial dilution is the stepwise dilution of a substance in solution. Usually the dilution factor at each step is constant, resulting in a geometric progression of the concentration in a logarithmic fashion. A ten-fold serial dilution could be 1 M, 0.1 M, 0.01 M, 0.001 M ... Serial dilutions are used to accurately create highly diluted solutions as well as solutions for experiments resulting in concentration curves with a logarithmic scale. A tenfold dilution for each step is called a logarithmic dilution or log-dilution, a 3.16-fold (100.5-fold) dilution is called a half-logarithmic dilution or half-log dilution, and a 1.78-fold (100.25-fold) dilution is called a quarter-logarithmic dilution or quarter-log dilution. Serial dilutions are widely used in experimental sciences, including biochemistry, pharmacology, microbiology, and physics. In biology and medicine In biology and medicine, besides the more conventional uses described above, serial dilution may also be used to red ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Germ-free Animal
Germ-free organisms are multi-cellular organisms that have no microorganisms living in or on them. Such organisms are raised using various methods to control their exposure to viral, bacterial or parasitic agents. When known microbiota are introduced to a germ-free organism, it usually is referred to as a gnotobiotic organism, however technically speaking, germ-free organisms are also gnotobiotic because the status of their microbial community is ''known''. Due to lacking a microbiome, many germ-free organisms exhibit health deficits such as defects in the immune system and difficulties with energy acquisition. Typically germ-free organisms are used in the study of a microbiome where careful control of outside contaminants is required. Generation and cultivation Germ-free organisms are generated by a variety of different means, but a common practice shared by many of them is some form of sterilization step followed by seclusion from the surrounding environment to prevent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Q Fever
Q fever or query fever is a disease caused by infection with ''Coxiella burnetii'', a bacterium that affects humans and other animals. This organism is uncommon, but may be found in cattle, sheep, goats, and other domestic mammals, including cats and dogs. The infection results from inhalation of a spore-like small-cell variant, and from contact with the milk, urine, feces, vaginal mucus, or semen of infected animals. Rarely, the disease is tick-borne. The incubation period is 9–40 days. Humans are vulnerable to Q fever, and infection can result from even a few organisms. The bacterium is an obligate intracellular pathogenic parasite. Signs and symptoms Incubation period is usually two to three weeks. The most common manifestation is flu-like symptoms: abrupt onset of fever, malaise, profuse perspiration, severe headache, muscle pain, joint pain, loss of appetite, upper respiratory problems, dry cough, pleuritic pain, chills, confusion, and gastrointestinal s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intracellular Parasite
Intracellular parasites are microparasites that are capable of growing and reproducing inside the cells of a host. Types of parasites There are two main types of intracellular parasites: Facultative and Obligate. Facultative intracellular parasites are capable of living and reproducing in or outside of host cells. Obligate intracellular parasites, on the other hand, need a host cell to live and reproduce. Many of these types of cells require specialized host types, and invasion of host cells occurs in different ways. Facultative Facultative intracellular parasites are capable of living and reproducing either inside or outside cells. Bacterial examples include: *''Bartonella henselae'' *''Francisella tularensis'' *''Listeria monocytogenes'' * ''Salmonella'' Typhi *''Brucella'' *''Legionella'' *''Mycobacterium'' *'' Nocardia'' *''Neisseria'' *''Rhodococcus equi'' *''Yersinia'' *''Staphylococcus aureus'' Fungal examples include: *''Histoplasma capsulatum''. *''Cryptococcus neofo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microbiological Culture
A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture medium under controlled laboratory conditions. Microbial cultures are foundational and basic diagnostic methods used as a research tool in molecular biology. The term ''culture'' can also refer to the microorganisms being grown. Microbial cultures are used to determine the type of organism, its abundance in the sample being tested, or both. It is one of the primary diagnostic methods of microbiology and used as a tool to determine the cause of infectious disease by letting the agent multiply in a predetermined medium. For example, a throat culture is taken by scraping the lining of tissue in the back of the throat and blotting the sample into a medium to be able to screen for harmful microorganisms, such as ''Streptococcus pyogenes'', the causative agent of strep throat. Furthermore, the term culture is more generally used informally ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coxiella Burnetii
''Coxiella burnetii'' is an obligate intracellular bacterial pathogen, and is the causative agent of Q fever. The genus ''Coxiella'' is morphologically similar to ''Rickettsia'', but with a variety of genetic and physiological differences. ''C. burnetii'' is a small Gram-negative, coccobacillary bacterium that is highly resistant to environmental stresses such as high temperature, osmotic pressure, and ultraviolet light. These characteristics are attributed to a small cell variant form of the organism that is part of a biphasic developmental cycle, including a more metabolically and replicatively active large cell variant form. It can survive standard disinfectants, and is resistant to many other environmental changes like those presented in the phagolysosome. History and naming Research in the 1920s and 1930s identified what appeared to be a new type of ''Rickettsia'', isolated from ticks, that was able to pass through filters. The first description of what may have been ''Coxi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gnotobiotic Animal
Gnotobiosis (from Greek roots ''gnostos'' "known" and ''bios'' "life") refers to an engineered state of an organism in which all forms of life (i.e., microorganisms) in or on it, including its microbiota, have been identified. The term gnotobiotic organism, or gnotobiote, can refer to a model organism that is colonized with a specific community of known microorganisms (isobiotic or defined flora animal) or that contains no microorganisms ( germ-free) often for experimental purposes. The study of gnotobiosis and the generation of various types of gnotobiotic model organisms as tools for studying interactions between host organisms and microorganisms is referred to as gnotobiology. History The concept and field of gnotobiology was born of a debate between Louis Pasteur and Marceli Nencki in the late 19th century, in which Pasteur argued that animal life needed bacteria to succeed while Nencki argued that animals would be healthier without bacteria, but it wasn't until 1960 that the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxygen Saturation
Oxygen saturation (symbol SO2) is a relative measure of the concentration of oxygen that is dissolved or carried in a given medium as a proportion of the maximal concentration that can be dissolved in that medium at the given temperature. It can be measured with a dissolved oxygen probe such as an oxygen sensor or an optode in liquid media, usually water. The standard unit of oxygen saturation is percent (%). Oxygen saturation can be measured regionally and noninvasively. Arterial oxygen saturation (SaO2) is commonly measured using pulse oximetry. Tissue saturation at peripheral scale can be measured using NIRS. This technique can be applied on both muscle and brain. In medicine In medicine, oxygen saturation refers to ''oxygenation'', or when oxygen molecules () enter the tissues of the body. In this case blood is oxygenated in the lungs, where oxygen molecules travel from the air into the blood. Oxygen saturation (() sats) measures the percentage of hemoglobin binding s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cloning
Cloning is the process of producing individual organisms with identical or virtually identical DNA, either by natural or artificial means. In nature, some organisms produce clones through asexual reproduction. In the field of biotechnology, cloning is the process of creating cloned organisms (copies) of Cell (biology), cells and of DNA fragments (molecular cloning). Etymology Coined by Herbert J. Webber, the term clone derives from the Ancient Greek word (), ''twig'', which is the process whereby a new plant is created from a twig. In botany, the term ''lusus'' was used. In horticulture, the spelling ''clon'' was used until the early twentieth century; the final ''e'' came into use to indicate the vowel is a "long o" instead of a "short o". Since the term entered the popular lexicon in a more general context, the spelling ''clone'' has been used exclusively. Natural cloning Cloning is a natural form of reproduction that has allowed life forms to spread for hundreds of millio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PNAS
''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] |
Experiment
An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into Causality, cause-and-effect by demonstrating what outcome occurs when a particular factor is manipulated. Experiments vary greatly in goal and scale but always rely on repeatable procedure and logical analysis of the results. There also exist natural experiment, natural experimental studies. A child may carry out basic experiments to understand how things fall to the ground, while teams of scientists may take years of systematic investigation to advance their understanding of a phenomenon. Experiments and other types of hands-on activities are very important to student learning in the science classroom. Experiments can raise test scores and help a student become more engaged and interested in the material they are learning, especially when used over time. Experiments can vary from personal and in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
