Bacterial Culture Media
- A culture medium is referred to as a solid or liquid preparation used to grow, transport, and store microorganisms.
- All microorganisms need sources of energy and macro-and micronutrients, the precise composition of a satisfactory medium depends on the species being cultivated due to the great variety of nutritional requirements.
- To be effective, a culture medium must contain all the nutrients the microorganism requires for growth.
- Frequently a medium is used to select and grow specific microorganisms or to help identify a particular species.
- Media can also be specifically designed to facilitate the growth of one type of microbe present in a sample from nature.
Ingredients of Bacterial Culture Media
The basic constituents of culture media include the following:
- The beef extract is an aqueous extract of lean beef tissue is concentrated in a paste.
- Function: Contains the water-soluble substances of animal tissue, which include carbohydrates, organic nitrogen compounds, water-soluble vitamins, and salts.
- Peptone is a product resulting from the digestion of proteinaceous materials, such as, meat, casein, and gelatin.
- The digestion of the protein material is accomplished with acids or proteolytic enzymes (such as pepsin, trypsin, or papain).
- Many different peptones (depending upon the protein used and the method of digestion) are available for use in bacteriological media: peptones differ in their ability to support the growth of bacteria.
- Function: The principal source of organic nitrogen; may also contain some vitamins and sometimes carbohydrates, depending upon the kind of proteinaceous material digested.
Gelling Agents or Agar
- Agar is a complex carbohydrate obtained from certain marine algae: processed to remove extraneous substances.
- Agar is obtained from agarophyte sea-weeds mainly Gelidium, Gracilaria and Pterocladia species. It is extracted as an aqueous solution at greater than 100°C, decolourised, filtered, dried and milled to a powder.
- Agar is chiefly composed of A long-chain polysaccharide, consisting of D-galactopyranose units; A variety of inorganic salts, minute quantities of protein-like materials, traces of long-chain fatty acids; and Minerals, such as calcium and magnesium.
- Agar, dissolved in aqueous solutions.
- It becomes gels when the temperature is reduced below 45°C.
- Agar is not considered a source of nutrients to the bacteria.
- Agar is usually used in a concentration of 2–3%.
- Agar is hydrolyzed at high temperatures and at high acid or alkaline pH.
- Gelatin is still used for a few specific media and carrageenans, alginates, silica gel and polyacrylamides are sometimes used as gelling agents,
- Function: Used as a solidification agent for media. It is the main component that is used universally for the preparation of solid media.
- It is an aqueous extract of yeast cells.
- Commercially available as a powder
- Function: A very rich source of the B vitamins and also contain organic nitrogen and carbon components.
- To make the culture media selective for certain micro-organisms, Chemicals or antimicrobials are added to it.
- These agents are preferred and added at particular concentrations to hinder the growth of undesired organisms in a polymicrobial sample.
- Some examples of common chemical selective agents are bile salts, dye-stuffs, selenite, tetrathionate, tellurite and azide.
- Antimicrobial agents are generally applied in mixtures when defeating polymicrobial contaminating flora. Antimicrobials are more specific in their selective action than the chemical agents shown above.
- colored indicator substances is added to detect the fermentation of specific carbohydrates within a culture medium.
- Indicator Substances should change colour distinctly and rapidly at critical pH values.
- Some examples of Indicator substances are e.g. phenol red, bromo-cresol purple, fuchsin, etc.,
- The use of buffer compounds at specific pK values is especially necessary when fermentable carbohydrates are added as energy sources.
- Some common examples of buffering agents that may be added to culture media are; Phosphates, acetates, citrates, zwitterion compounds and specific amino-acids.
Essential Metals and Minerals
- A media should contain macro-components and micro-components.
- Some examples of micro-components (mgm-microgm/litre) are; Zn, Mn, Br, B, Cu, Co, Mo, V, Sr, etc.
- Some examples of macro-components (gm/litre) are; Zn, Mn, Br, B, Cu, Co, Mo, V, Sr, etc.
- Glucose is the most important component is added to bacterial culture media as a source of energy to increase the rate of growth of organisms.
- Other carbohydrates may be used as required.
- Carbohydrates are added to media at 5-10 grams per litre.
- Other common ingredients of media include water, sodium chloride and other electrolytes, meat extract, malt extract, blood, and serum. Meat extract is available commercially as Lab-Lemco and contains inorganic salts, carbohydrates, certain growth factors, and protein degradation products.
- Blood or serum is usually used for enriching culture of bacteria. Usually, 5–10% defibrinated sheep or human blood is used.
Serum in media
Serum contains a diverse mixture of growth factors, albumins as well as growth inhibiters [3232. Serum is among the essential elements of the cell culture media and is an amino acid source as well as proteins as well as vitamin supplements (particularly fat-soluble vitamins, such as D, D, E, and K) carbohydrate and lipids, hormones, the growth factor, mineral as well as trace elements. The serum of calf and fetal bovines are typically utilized to aid in the growth of the cells in culture. Fetal serum is an abundant supply of growth-promoting factors, and is suitable for cloning cells as well as for the growth of cells that are fastidious. The use of calf serum in studies of contact inhibition due to its lower capacity to promote growth. Normal growth media usually comprise 2-10% serum. The supplementation of media with serum has the following benefits :
Serum supplies the most basic nutrition (both within the solution and linked to Proteins) that cells require.
Serum is a source of several growing factors as well as hormones which are involved in growth stimulation and cell function.
- It contains a variety of binding proteins such as transferrin, albumin, which carry various other molecules into cells. For example: albumin carries lipids, vitamins, hormones, etc. into cells.
- It also provides proteins, such as fibronectin, that aid in the adhesion of cells to the substrate. It also supplies spreading factors that allow the cells spread before they begin to divide.
- It is a protease inhibitor that can shield cells from proteolysis.
- It also contains minerals, such as the minerals Na+ and K+ Zn2+ etc.
- It improves the viscosity of the medium, which in turn, shields cells from mechanical harm when suspension cultures are agitated.
- It also serves as an intermediary.
Because of the presence of inhibitors as well as growth factors, function of serum in the cell culture process is extremely complex. In addition to fulfilling a variety of roles using serum in the context of tissue culture is not without its disadvantages. Table outlines the advantages and disadvantages of using serum within the medium.
|Benefits from serums in media||Disadvantages of serums in media|
|Serum is a source of many growing factors as well as hormones that can stimulate cell growth and function.||Uncertainty within the composition and composition of the serum|
|Aids in the connection of cells||It is essential to conduct tests to ensure the quality of each batch prior to use|
|Spreads the word about||Might contain some factors that inhibit growth|
|acts like a buffer agent that assists in maintaining the pH of the media culture||Increase the chance of contamination|
|It functions in the role of a binding protein||The presence of serum in media can interfere with separation and purification of products from cells|
|Reduces mechanical damage and the damage caused by viscosity|
Bacterial culture media classification
Culture media can be classified based on several parameters:
- the chemical constituents from which they are made
- their physical nature, and
- their function.
Classification of Culture Media based on Chemical Composition
Based on Chemical Composition bacterial culture media is divided into three following groups;
- Defined or synthetic medium
- Complex media
- Simple media
Defined or synthetic medium
- A defined medium, also known as synthetic medium, contains known quantities of all ingredients.
- All the chemicals used are known, and it does not contain any animal, yeast, or plant tissue.
- Defined or synthetic medium contain trace elements and vitamins.
- It also contains a defined carbon source and nitrogen source required by certain microbes.
- Defined or synthetic medium can be in liquid form (broth) or solidified by an agent such as agar.
- It is often used to culture photosynthetic microbes that use CO2 as a carbon source and light as an energy source.
- It contains sodium carbonate or bicarbonate as a source of CO2, and nitrate or ammonia as a nitrogen source, sulfate, phosphate, and other minerals.
- Example of a Defined or synthetic medium is Dubos’ medium with Tween 80, B-11 medium for cyanobacteria, Medium for E. coli.
B-11 medium for cyanobacteria Composition
- NaNO3 – 1.5g/lit
- K2HPO4.3H2O – 0.04 g/lit
- MgSO4. 7H2O – 0.075 g/lit
- CaCl2. 7H2O – 0.036 g/lit
- Citric Acid – 0.006 g/lit
- Ferric ammonium citrate – 0.006 g/lit
- EDTA (Na2Mg Slat) – 0.001 g/lit
- Na2Co3 – 0.02 g/lit
- Trace metal solution – 1.0 ml/lit
- Final pH 7.4
Medium for E. coli. Composition
- Glucose – 1.0 g/lit
- Na2HPO4 – 16.4 g/lit
- KH2PO4 – 1.5 g/lit
- (NH4)2SO4 – 2.0 g/lit
- MgSO4. 7H2O – 0.2 g/lit
- CaCl2 – 0.01 g/lit
- FeSO4. 7H2O – 0.0005 g/lit
- Final pH 6.8 -7
- Media that contain some ingredients of unknown chemical composition are known as complex media.
- Most of the media other than basal media are usually known as complex media [e.g., chocolate agar, MacConkey agar, Robertson’s cooked meat (RCM) medium, Lowenstein–Jensen (LJ) medium, etc.].
- Complex media have some complex ingredients, which consist of a mixture of many chemicals in unknown proportions.
- This is an undefined medium because the amino acid source contains a variety of compounds with the exact composition unknown.
- They are very useful because a single complex medium may be able to meet all the nutritional requirements of many different microorganisms.
- Complex media often are needed because the nutritional requirements of a particular microorganism are unknown, and thus a defined medium cannot be formulated.
- Complex media are also used to culture fastidious microbes, those with complicated nutritional or cultural requirements.
- Most complex media contain undefined components such as peptones, meat extract, and yeast extract.
- Peptones are protein hydrolysates prepared by partial proteolytic digestion of meat, casein, soya meal, gelatin, and other protein sources. They serve as sources of carbon, energy, and nitrogen.
- Beef extract and yeast extract are aqueous extracts of lean beef and brewer’s yeast, respectively. Beef extract contains amino acids, peptides, nucleotides, organic acids, vitamins, and minerals.
- Yeast extract is an excellent source of B vitamins as well as nitrogen and carbon compounds.
- Examples of complex media are nutrient broth, tryptic soy broth, and MacConkey agar
- The simple or basal media include nutrient broth and peptone water, which form the basis of other media
- Example of simple media is Nutrient broth, Nutrient agar.
- Nutrient broth is an example of a simple liquid medium that consists of peptone, meat extract, sodium chloride, and water. Addition of 0.5% glucose to nutrient broth makes it glucose broth.
- Nutrient agar is an example of a simple solid medium. The medium is used routinely for isolation of many bacteria from clinical specimens.
Classification of Culture Media based on Physical Nature
Based on Physical Nature, the bacterial Culture Media is divided into three groups such as;
- Liquid media
- Semisolid Media
- Solid Media
- Liquid media provide greater sensitivity for the isolation of small numbers of microorganisms.
- Examples of liquid media include nutrient broth, sugar media, and enrichment media.
Disadvantages of Liquid media
- Identification of mixed cultures growing in liquid media requires subculture onto solid media so that isolated colonies can be processed separately for identification.
- Growth in liquid media also cannot ordinarily be quantitated.
- Bacteria grown in liquid cultures often form colloidal suspensions.
Composition and uses of some common liquid media
- Composition: Peptone water is composed of Peptone, sodium chloride, water.
- Uses: Used as a Routine culture, base for sugar fermentation test, indole test.
- Composition: Nutrient broth is composed of Peptone water and meat extract.
- Uses: Use as Routine culture.
- Composition: Glucose broth is composed of Nutrient broth, glucose
- Uses: Blood culture, culture of fastidious organisms, such as streptococci
Brain heart infusion broth
- Composition: Brain heart infusion broth is composed of Sodium citrate, sodium chloride, sodium phosphate, dextrose peptone, brain and heart infusion broth (ox), sodium polyanethol sulfonate (SPS)
- Uses: Used to study Whole blood, bone marrow, body fluid culture.
Alkaline peptone water
- Composition: Alkaline peptone water is composed of Peptone water (pH 8.6)
- Uses: used as an Enrichment medium for Vibrio
- Composition: Selenite-F broth is composed of Peptone water, sodium selenite.
- Uses: Used as an Enrichment medium for feces for Salmonella and Shigella.
- Composition: Tetrathionate broth is composed of Nutrient broth, sodium thiosulfate, calcium carbonate, iodine solution
- Uses: Use as a Culture of feces for Salmonella
Robertson’s cooked meat (RCM) broth
- Composition: Nutrient broth, predigested cooked meat of ox heart
- Uses: Use as an Anaerobic bacterial culture.
- Semisolid media, prepared with agar at concentrations of 0.5 percent or less, have a soft, custardlike consistency.
- Semisolid Media useful for the cultivation of microaerophilic bacteria (see Gaseous Requirements later in this chapter) or for the determination of bacterial motility.
- The solid media contain a solidifying agent which is usually agar, at a concentration of 1.5 to 2.0 percent forms firm, transparent gels that are not degraded by most bacteria.
- Silica gel is sometimes used as an inorganic solidifying agent for autotrophic bacteria.
- Solid media are useful for isolating bacteria or for determining the characteristics of colonies.
- Agar is used as a solidifying agent in most culture media.
- By varying the concentration of agar, it is possible to make the medium solid or semisolid.
- Solid media, though somewhat less sensitive than liquid media, provide isolated colonies that can be quantified and identified.
- Some genera and species can be recognized on the basis of their colony morphologies in solid media.
- A common example of Solid Media is Nutrient agar, which is prepared by adding 2% agar to nutrient broth is the simplest and most common medium used routinely in diagnostic laboratories.
- Other examples of solid media include blood agar, chocolate agar, MacConkey agar, etc.
Composition and uses of some common solid media
- Composition: Nutrient agar is composed of Nutrient broth, and agar 2%.
- Uses: Routine culture
- Composition: MacConkey medium is composed of Peptone, lactose, sodium taurocholate, agar, neutral red
- Uses: It is used as a Culture of Gramnegative bacteria, such as Escherichia coli.
- Composition: Nutrient agar, 5% sheep or human blood
- Uses: Routine culture, culture of fastidious organisms, such as Streptococcus spp.
- Composition: Heated blood agar
- Uses: Use as a Culture of Haemophilus influenzae and Neisseria.
Deoxycholate citrate agar
- Composition: Nutrient agar, sodium deoxycholate, sodium citrate, lactose, neutral red, etc.
- Uses: Culture of Shigella spp. and Salmonella spp.
Thiosulfate citrate bile salt sucrose agar
- Composition: Thiosulfate, citrate, bile salt, sucrose, bromothymol blue, thymol blue
- Use: Culture of Vibrio cholerae
Loeffler’s serum slope
- Composition: Nutrient broth, glucose, horse serum.
- Uses: Culture of Corynebacterium diphtheriae.
Lowenstein Jensen medium
- Composition: Coagulated hen’s egg, mineral salt solution, asparagine, malachite green
- Uses: Culture of Mycobacterium tuberculosis
Classification of Culture Media based on Function/Application
Many special-purpose media are needed to facilitate recognition, enumeration, and isolation of certain types of bacteria. To meet these needs, the microbiologist classified cultural media into the following categories based on their application;
- Selective media
- Differential or indicator media
- Transport media
- Selective media allow the growth of particular microorganisms, while inhibiting the growth of others.
- For example, many Gram-negative bacteria will grow on media containing bile salts or dyes such as basic fuchsin and crystal violet; however, the growth of Gram-positive bacteria is inhibited.
Example of Selective media
- Eosin methylene blue agar and MacConkey agar are widely used for the detection of E. coli and related bacteria in water supplies and elsewhere. These media suppress the growth of Gram-positive bacteria.
- Thiosulfate citrate bile salt sucrose agar (TCBS) selective for the isolation of Vibrio cholerae
- Deoxycholate citrate agar (DCA) selective for enteric bacilli, such as Salmonella spp. and Shigella spp.
- LJ medium selective for Mycobacterium tuberculosis.
- Hektoen enteric (HE) agar selective for Gram-negative bacteria.
- Mannitol salt agar (MSA) selective for Gram-positive bacteria.
- Xylose lysine desoxycholate (XLD) agar selective for Gram-negative bacteria.
- Buffered charcoal yeast extract agar selective for certain Gram-negative bacteria, such as Legionella pneumophila.
|Medium||Colony characteristics||Organisms inhibited|
|Mannitol salt agar||Big yellow colonies of Staphylococcus aureus, Small pink colonies of Staphylococcus epidermidis||Streptococcus|
|Gray colonies of Neisseria meningitidis and Neisseria gonorrhoeae||Gram-positive cocci|
|MacConkey agar medium||Lactose fermenters: red colonies, e.g., Escherichia coli.|
Lactose nonfermenters: colorless colonies of Salmonella spp.
|Thiosulfate citrate bile salt sucrose agar||Sucrose fermenter: yellow colonies of Vibrio cholerae.|
Sucrose nonfermenters: green colonies of Vibrio parahaemolyticus
|Charcoal yeast extract||Cut glass colonies of Legionella spp.||Gram-positive cocci|
|Lowenstein– Jensen medium||Rough, tough, and buff colonies of Mycobacterium tuberculosis.|
Smooth and pigmented colonies of atypical Mycobacterium spp.
|Sabouraud’s dextrose agar||Most fungi||Most bacteria|
Differential or indicator media
- Differential media are media that distinguish among different groups of microbes and even permit tentative identification of microorganisms based on their biological characteristics.
- When Certain reagents or supplements, incorporated into culture media, may allow differentiation of various kinds of bacteria.
- For example, if a mixture bacteria is inoculated onto a blood-containing agar medium (blood agar), some of the bacteria may hemolyze (destroy) the red blood cells: others do not. Thus one can distinguish between hemolytic and nonhemolytic bacteria on the same medium.
- Differential or indicator media basically help to distinguish one microorganism from another growing on the same media by their growth characteristics.
- Differential or indicator media depend on the biochemical properties of a microorganism growing in the presence of specific nutrients or indicators, such as neutral red, phenol red, eosin, or methylene blue.
- Blood agar is both a differential medium and an enriched one.
- The medium changes color when a bacterium grows in them.
- For example, S. typhi grows as black colonies on Wilson and Blair medium containing sulfite. Lactose fermenting bacteria, such as E. coli produce pink colonies, whereas non-lactose fermenting bacteria, such as Salmonella spp. form pale or colorless colonies on MacConkey agar. Fermentation of lactose in the medium makes it acidic and leads to the formation of pink colonies in the presence of neutral red.
Examples of differential media include
- Eosin methylene blue (EMB), differential for lactose and sucrose fermentation;
- MacConkey, differential for lactose fermentation;
- Mannitol salt agar (MSA), differential for mannitol fermentation; and
- X-gal plates, differential for lac operon mutants for detection of recombinant strains of bacteria for study in molecular biology.
- Transport media are used to maintain the viability of certain delicate organisms in clinical specimens during their transport to the laboratory.
- They typically contain only buffers and salt.
- They lack carbon, nitrogen, and organic growth factors, hence do not facilitate microbial multiplication.
- Examples of transport media are Stuart’s transport medium for Neisseria gonorrhoeae.
- The enriched media are invariably solid media that facilitate growth of certain fastidious bacteria.
- These media are prepared by adding substances like blood, serum, and egg to the basal media in order to meet the nutritional requirements of more exacting and more fastidious bacteria.
- Examples of enriched media are Blood agar, chocolate agar, Loeffler’s serum slope (LSS), and LJ medium.
- Blood agar is an enriched medium in which nutritionally rich whole blood supplements constitute the basic nutrients.
- Chocolate agar is enriched with heat-treated blood (80°C), which turns brown and gives the medium the color for which it is named.
- Enrichment media are liquid media that stimulate the growth of certain bacteria or suppress the growth of others for isolation of desired pathogenic bacteria.
- Commensal bacteria, such as Escherichia coli present in feces, tend to overgrow pathogenic ones in stool specimens. In such situations, enrichment media (such as selenite-F broth or tetrathionate broth) are used for the isolation of Salmonella Typhi and Shigella spp. from feces.
- Media of prescribed compositions are used for the assay of vitamins, amino acids, and antibiotics, Media of special composition are also available for testing disinfectants.
- An example of Assay Media is; antibiotic assay media are used for determining antibiotic potency by the microbiological assay technique.
- It is Specific kinds of media are used for determining the bacterial content of such materials as milk and water.
- Their composition must adhere to prescribed specifications.
- Basically, Enumeration Media is used to enumerate the number of bacterial cells within a sample.
- Characterization Media are conventionally used to determine the type of growth produced by bacteria, as well as to determine their ability to produce certain chemical changes
- Satisfactory maintenance of the viability and physiological characteristics of a culture over time may require a medium different from that which is optimum for growth. Prolific, rapid growth may also be associated with rapid death of the cells at the end of the growth phase.
- For example, glucose in a medium frequently enhances growth, but acid harmful to the cells is likely to be produced. Therefore, omission of the glucose is preferable in maintenance medium.
Preparation of bacterial culture media
The preparation of bacteriological media usually involves the following steps:
- Each ingredient, or the complete dehydrated medium, is dissolved in the appropriate volume of distilled water.
- The pH of the fluid medium is determined with a pH meter and adjusted if necessary.
- If a solid medium is desired, agar is added and the medium is boiled to dissolve the agar.
- The medium is dispensed into tubes or flasks.
- The medium is sterilized, generally by autoclaving. Some media for specific ingredients) that are heat-labile are sterilized by filtration.
Applications of bacterial culture
There are a variety of reasons it is possible or desirable to grow bacteria. In this article, we will look at some of the more common uses.
Diagnosis of the infection
Despite the time required to isolate and determine bacteria from the sample, bacterial culture is still a vital diagnostic tool.12 Although PCR can quickly identify any particular pathogen, identifying the cause can confirm that the pathogen remains alive and alerting scientists to possible transmission risks and providing the treatment. Also, the bacterial strain could be further investigated for further specific information such as sensitivity to antibiotics as well as directing treatment decisions. The strains can be saved to be used in the future to be used for instance for monitoring of diseases.
It is possible to alter the genomes of bacteria for a variety of reasons. For example, seeking to comprehend the fundamental biological process, to reduce it when making vaccine strains, or to increase the production of proteins and then make a reference strain that has the ability to detect a marker, to name only a few. If you are mutating, deletion or introducing genetic material it is essential to establish the desired strain prior to or after the process of genetic engineering.
Study of epidemiology
Characterizing and cultivating bacteria can be crucial for epidemiological studies.14 Scientists can analyze how populations of bacterial species change in time. This can guide therapeutic, vaccine and diagnostic designs and updates, and also examine transmission events that can help inform public health policies and guidelines. In the Gonococcal Isolate Surveillance project (GISP) is a good example of a project that studies strains that are resistant to antibiotics which aids in the formulation of treatment recommendations for drugs. It is run by the Centers for Disease Control and Prevention (CDC) also manages an active Bacterial Core monitoring (ABCs) system that provides monitoring in the laboratory and across the population of pathogens that are invasive and of important to public health.
Scale up to allow the study of omics
Although the sequencing of DNA or RNA may be done with small quantities of genetic material even at the single-cell scale, for the majority of research Next-Generation Sequencing (NGS) is still carried out on bacteria. As therefore, bacteria typically require a culture in order to prepare DNA and the RNA extraction.15 If you’re seeking one particular strain (unlike microbiome research which may include an assortment of) the strain will originate from a pure culture.
Develop therapeutics and vaccines
In order to combat an bacterial pathogen generally, you must be able of cultivating the pathogen as well. In the course of developing vaccines, it is possible to isolate strains of bacteria to learn their genomes and amplify their genes, or alter the genes. Additionally, to test potential therapies or vaccines in the course of testing, it is usually essential to conduct challenge tests17 that test subjects with the pathogen to test whether the treatment is effective. For this it is necessary to grow the bacterial strain usually grown and, within an established challenge model recorded to monitor and measure the amount that the subjects are exposed to.
Production of food and beverages
Bacteria are a crucial component of the process of making numerous foods. They are divided into starter and probiotic culture.
Probiotics are typically cultivated for their health benefits,18 usually through our gut microbiome. Although probiotics could include a variety of species of bacterial, Lactobacillus as well as Bifidobacterium are the most popular selections to cultivate.
Starter culture, however, are often used as a an element of a food production process to enhance flavor, texture and nutritional value, or to improve preservation. Examples include sourdough loaves, salami, 19 pepperoni, and dried salami. Bacteria that cause lactic acid (LAB) are often present in the starter cultures. Certain foods and beverages might, however, be between the two camps like yogurt, and the ever-popular Kimchi20 and Kombucha, where the products are consumed to enjoy their taste and probiotic benefits.
Whatever the reason that a culture is designed to serve keeping a clean environment that is free of contaminants is crucial for the highest quality production and consumer security.
Food contaminants can be detected
Although some bacteria are useful in food production however, they could also be contamination and could be able be a cause of serious food-borne illness. The most common causes are Salmonella as well as., Listeria monocytogenes, Campylobacter jejuni, and E. coli. It is crucial that the analysts can cultivate any potentially harmful bacteria in food samples, even if they’re present in small amounts.
Types of Animal Cell Culture Media
Cells from animals can be cultivated with a organic medium, or using an artificial or synthetic medium together with some natural substances.
Natural media comprise only of biological fluids that naturally occur. Natural media are extremely useful and are suitable for a large spectrum of animal cell culture. One of the major drawbacks of using natural media is its low reproducibility because of the ignorance of the precise composition of these natural media.
The synthetic or artificial mediums are made by combining ingredients (both organic and non-organic) including vitamins, salts CO2 and O2 gas phases and blood proteins, carbohydrates, cofactors. Artificial media are created to meet one or one or more of the following functions 1)) instant survival (a balanced salt solution with a specific pH and Osmotic pressure) 2.) extended life (a healthy salt solution that is supplemented with various organic substances and/or serum) 3.) unending growth; 4) special roles.
Artificial media are classified in four types:
Serum containing media
Fetal bovine serum can be described as the most commonly used ingredient in the culture of animal cells. It is an inexpensive supplement that can provide the best culture environment. Serum acts as a carrier or chelator for water-insoluble and labile nutrients, hormones , growth factors, inhibitors of protease and neutralizes toxic molecules.
The presence of serum in media is not without its drawbacks. It can result in serious misinterpretations when studying immunology. Many serum-free media are being developed. They are usually made to help in the cultivation of a particular type of cell like Knockout Serum Replacement or Knockout the DMEM of Thermo Fisher Scientific, and the mTESR medium of Stem Cell Technologies, for stem cells. They contain specified amounts of growth factors purified such as lipoproteins and proteins, that are typically provided by serum. These media are often called ‘defined culture media’ because the components of these media are well-known.
Chemically defined media
They contain non-contamination organic and inorganic components, and can contain protein-based additives that are pure like growth factors. The constituents of these media are created in yeast or bacteria by genetic engineering and the inclusion of cholesterol, vitamins as well as specific amino acids and fatty acids.
Media that is protein-free
Protein-free media are not enriched with any protein, and are only composed of non-protein components. In comparison to serum-supplemented media the use of non-protein media encourages higher cell growth and expression of proteins and aids in the downstream purification of any express product. Formulations such as MEM, RPMI-1640, are all protein-free and protein supplementation is available as needed.