Misplaced Pages

#336663

31-1098: R2A agar ( Reasoner's 2A agar ) is a culture medium developed to study bacteria which normally inhabit potable water . These bacteria tend to be slow-growing species and would quickly be suppressed by faster-growing species on a richer culture medium. Since its development in 1985, it has been found to allow the culturing of many other bacteria that will not readily grow on fuller, complex organic media. Final pH 7.2 ± 0.2 @ 25 °C Culture medium The two major types of growth media are those used for cell culture , which use specific cell types derived from plants or animals, and those used for microbiological culture , which are used for growing microorganisms such as bacteria or fungi . The most common growth media for microorganisms are nutrient broths and agar plates ; specialized media are sometimes required for microorganism and cell culture growth. Some organisms, termed fastidious organisms , require specialized environments due to complex nutritional requirements. Viruses , for example, are obligate intracellular parasites and require

62-418: A certain metabolite . Normally, the presence of a specific gene or an allele of a gene confers upon the cell the ability to grow in the selective medium. In such cases, the gene is termed a marker . Selective growth media for eukaryotic cells commonly contain neomycin to select cells that have been successfully transfected with a plasmid carrying the neomycin resistance gene as a marker. Gancyclovir

93-462: A growth medium containing living cells. The most common growth media for microorganisms are nutrient broths (liquid nutrient medium) or lysogeny broth medium. Liquid media are often mixed with agar and poured via a sterile media dispenser into Petri dishes to solidify. These agar plates provide a solid medium on which microbes may be cultured. They remain solid, as very few bacteria are able to decompose agar (the exception being some species in

124-502: A minimal medium varies enormously depending on which microorganism is being grown. Minimal media are those that contain the minimum nutrients possible for colony growth, generally without the presence of amino acids, and are often used by microbiologists and geneticists to grow "wild-type" microorganisms. Minimal media can also be used to select for or against recombinants or exconjugants . Minimal medium typically contains: Supplementary minimal media are minimal media that also contains

155-423: A mixture of many chemical species in unknown proportions. Undefined media are sometimes chosen based on price and sometimes by necessity – some microorganisms have never been cultured on defined media. A good example of a growth medium is the wort used to make beer . The wort contains all the nutrients required for yeast growth, and under anaerobic conditions, alcohol is produced. When the fermentation process

186-433: A single selected agent, usually an amino acid or a sugar. This supplementation allows for the culturing of specific lines of auxotrophic recombinants. Selective media are used for the growth of only selected microorganisms. For example, if a microorganism is resistant to a certain antibiotic , such as ampicillin or tetracycline , then that antibiotic can be added to the medium to prevent other cells, which do not possess

217-512: Is aimed at achieving greater consistency and control in cell culture processes. Ultimately, the composition of the culture medium directly impacts cell viability and productivity, making the careful selection and design of culture media essential for successful mammalian cell culture. Fermentation (food) In food processing , fermentation is the conversion of carbohydrates to alcohol or organic acids using microorganisms — yeasts or bacteria —without an oxidizing agent being used in

248-552: Is an exception to the rule, as it is used to specifically kill cells that carry its respective marker, the Herpes simplex virus thymidine kinase. Examples of selective media: Differential or indicator media distinguish one microorganism type from another growing on the same medium. This type of media uses the biochemical characteristics of a microorganism growing in the presence of specific nutrients or indicators (such as neutral red , phenol red , eosin y , or methylene blue ) added to

279-496: Is an important factor to consider during the fermentation of foods. Failing to completely remove any microbes from equipment and storing vessels may result in the multiplication of harmful organisms within the ferment, potentially increasing the risks of food borne illnesses such as botulism. However, botulism in vegetable ferments is only possible when not properly canned. The production of off smells and discoloration may be indications that harmful bacteria may have been introduced to

310-401: Is an undefined medium because the amino-acid source contains a variety of compounds; the exact composition is unknown. A defined medium (also known as chemically defined medium or synthetic medium) is a medium in which Examples of nutrient media: A defined medium that has just enough ingredients to support growth is called a "minimal medium". The number of ingredients that must be added to

341-408: Is complete, the combination of medium and dormant microbes, now beer, is ready for consumption. The main types are Culture media contain all the elements that most bacteria need for growth and are not selective, so they are used for the general cultivation and maintenance of bacteria kept in laboratory culture collections. An undefined medium (also known as a basal or complex medium) contains: This

SECTION 10

#1732875963337

372-549: Is exacerbated when a plastic container is used for this purpose instead of the old-fashioned, traditional method, a grass-lined hole, as the Clostridium botulinum bacteria thrive in the anaerobic conditions created by the air-tight enclosure in plastic. Research has found that fermented food contains a carcinogenic by-product, ethyl carbamate (urethane). "A 2009 review of the existing studies conducted across Asia concluded that regularly eating pickled vegetables roughly doubles

403-437: Is made use of when fruit juices are converted to wine , when grains are made into beer , and when foods rich in starch, such as potatoes , are fermented and then distilled to make spirits such as gin and vodka . The production of carbon dioxide is used to leaven bread. The production of organic acids is exploited to preserve and flavor vegetables and dairy products. Food fermentation serves five main purposes: to enrich

434-549: The Nobel Prize in Chemistry for his research and discovery of "cell-free fermentation". One year earlier, in 1906, ethanol fermentation studies led to the early discovery of oxidized nicotinamide adenine dinucleotide (NAD ). Food fermentation is the conversion of sugars and other carbohydrates into alcohol or preservative organic acids and carbon dioxide . All three products have found human uses. The production of alcohol

465-422: The physiological relevance of findings from tissue culture experiments, especially for metabolic studies. In addition, the dependence of a cell line on a metabolic gene was shown to be affected by the media type. When performing a study involving several cell lines, utilizing a uniform culture media for all cell lines might reduce the bias in the generated datasets. Using a growth medium that better represents

496-415: The case of animal cells, this difficulty is often addressed by the addition of blood serum or a synthetic serum replacement to the medium. In the case of microorganisms, no such limitations exist, as they are often unicellular organisms . One other major difference is that animal cells in culture are often grown on a flat surface to which they attach, and the medium is provided in a liquid form, which covers

527-674: The cells. In contrast, bacteria such as Escherichia coli may be grown on solid or in liquid media. An important distinction between growth media types is that of chemically defined versus undefined media. A defined medium will have known quantities of all ingredients. For microorganisms, they consist of providing trace elements and vitamins required by the microbe and especially defined carbon and nitrogen sources. Glucose or glycerol are often used as carbon sources, and ammonium salts or nitrates as inorganic nitrogen sources. An undefined medium has some complex ingredients, such as yeast extract or casein hydrolysate, which consist of

558-1650: The diet through development of a diversity of flavors, aromas, and textures in food substrates; to preserve substantial amounts of food through lactic acid , alcohol, acetic acid , and alkaline fermentations; to enrich food substrates with protein, essential amino acids , and vitamins; to eliminate antinutrients ; and to reduce cooking time and the associated use of fuel. Cheonggukjang , doenjang , fermented bean curd , miso , natto , soy sauce , stinky tofu , tempeh , oncom, soybean paste, Beijing mung bean milk, kinama, iru , thua nao Amazake , beer , bread , choujiu , gamju , injera , kvass , makgeolli , murri , ogi , rejuvelac , sake , sikhye , sourdough , sowans , rice wine , malt whisky , grain whisky , idli , dosa , Bangla (drink) vodka , boza , and chicha , among others. Kimchi , mixed pickle , sauerkraut , Indian pickle , gundruk , tursu Wine , vinegar , cider , perry , brandy , atchara , nata de coco , burong mangga , asinan , pickling , vişinată , chocolate , rakı , aragh sagi , chacha , tempoyak Mead , metheglin , tej Some kinds of cheese also, kefir , kumis (mare milk), shubat (camel milk), ayran , cultured milk products such as quark , filmjölk , crème fraîche , smetana , skyr , and yogurt Bagoong , faseekh , fish sauce , Garum , Hákarl , jeotgal , ngapi , padaek , pla ra , prahok , rakfisk , shrimp paste , surströmming , shidal Chorizo , salami , sucuk , pepperoni , nem chua, som moo , saucisson , fermented sausage Pu-erh tea , Kombucha , Lahpet , Goishicha Sterilization

589-423: The fermentation of sugar to alcohol by yeast , Pasteur concluded that the fermentation was catalyzed by a vital force, called " ferments ", within the yeast cells. The "ferments" were thought to function only within living organisms. Pasteur wrote that "Alcoholic fermentation is an act correlated with the life and organization of the yeast cells, not with the death or putrefaction of the cells." Nevertheless, it

620-655: The fermentation process. The earliest archaeological evidence of fermentation is 13,000-year-old residues of a beer, with the consistency of gruel, found in a cave near Haifa in Israel. Another early alcoholic drink, made from fruit, rice, and honey, dates from 7000 to 6600 BC, in the Neolithic Chinese village of Jiahu , and winemaking dates from ca. 6000 BC, in Georgia , in the Caucasus area. Seven-thousand-year-old jars containing

651-502: The food. Alaska has witnessed a steady increase of cases of botulism since 1985. It has more cases of botulism than any other state in the United States of America. This is caused by the traditional Alaska Native practice of allowing animal products such as whole fish, fish heads, walrus , sea lion , and whale flippers, beaver tails, seal oil, and birds, to ferment for an extended period of time before being consumed. The risk

SECTION 20

#1732875963337

682-465: The genera: Cytophaga , Flavobacterium , Bacillus , Pseudomonas , and Alcaligenes ). Bacteria grown in liquid cultures often form colloidal suspensions . The difference between growth media used for cell culture and those used for microbiological culture is that cells derived from whole organisms and grown in culture often cannot grow without the addition of, for instance, hormones or growth factors which usually occur in vivo . In

713-441: The medium to visibly indicate the defining characteristics of a microorganism. These media are used for the detection of microorganisms and by molecular biologists to detect recombinant strains of bacteria. Examples of differential media: Transport media should fulfill these criteria: Examples of transport media: Enriched media contain the nutrients required to support the growth of a wide variety of organisms, including some of

744-441: The more fastidious ones. They are commonly used to harvest as many different types of microbes as are present in the specimen. Blood agar is an enriched medium in which nutritionally rich whole blood supplements the basic nutrients. Chocolate agar is enriched with heat-treated blood (40–45 °C or 104–113 °F), which turns brown and gives the medium the color for which it is named. The choice of culture medium might affect

775-430: The physiological levels of nutrients can improve the physiological relevance of in vitro studies and recently such media types, as Plasmax and human plasma-like medium (HPLM), were developed. The selection of cell culture medium is crucial for efficient mammalian cell culture, significantly affecting cell growth, productivity, and consistency across batches. In protein expression, the choice of media can also influence

806-413: The preservation of sour foods with the production of lactic acid , such as in sauerkraut and yogurt . Other widely consumed fermented foods include vinegar , olives , and cheese . More localised foods prepared by fermentation may also be based on beans, grain, vegetables, fruit, honey, dairy products, and fish. Natural fermentation predates human history. Since ancient times, humans have exploited

837-441: The reaction. Fermentation usually implies that the action of microorganisms is desired. The science of fermentation is known as zymology or zymurgy. The term "fermentation" sometimes refers specifically to the chemical conversion of sugars into ethanol , producing alcoholic drinks such as wine , beer , and cider . However, similar processes take place in the leavening of bread (CO 2 produced by yeast activity), and in

868-637: The remains of wine, now on display at the University of Pennsylvania, were excavated in the Zagros Mountains in Iran . There is strong evidence that people were fermenting alcoholic drinks in Babylon ca. 3000 BC, ancient Egypt ca. 3150 BC, pre-Hispanic Mexico ca. 2000 BC, and Sudan ca. 1500 BC. The French chemist Louis Pasteur founded zymology , when in 1856 he connected yeast to fermentation. When studying

899-424: The resistance, from growing. Media lacking an amino acid such as proline in conjunction with E. coli unable to synthesize it were commonly used by geneticists before the emergence of genomics to map bacterial chromosomes. Selective growth media are also used in cell culture to ensure the survival or proliferation of cells with certain properties, such as antibiotic resistance or the ability to synthesize

930-881: The therapeutic characteristics of produced proteins through processes like glycosylation. Different types of media, such as serum-containing, serum-free, protein-free, and chemically defined media, have distinct benefits and drawbacks. Serum-containing media are rich in growth factors but can lead to variability and contamination issues. Fetal bovine serum (FBS) is commonly used due to its high capacity to support cell growth, although it poses biosafety concerns due to its inconsistent composition. In contrast, serum-free media (SFM) offer standardized formulations that enhance reliability and reduce contamination risks. They are designed to include essential nutrients like amino acids, vitamins, and glucose, but can sometimes provide weaker growth performance compared to serum-containing alternatives. The development of protein-free and chemically defined media

961-453: Was known that yeast extracts can ferment sugar even in the absence of living yeast cells . While studying this process in 1897, the German chemist and zymologist Eduard Buchner of Humboldt University of Berlin , Germany, found that sugar was fermented even when there were no living yeast cells in the mixture, by an enzyme complex secreted by yeast that he termed zymase . In 1907 he received

R2A agar - Misplaced Pages Continue

#336663