Agar, or agar-agar, is a jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from "ogonori" (Gracilaria) and "tengusa" (Gelidiaceae). As found in nature, agar is a mixture of two components, the linear polysaccharide agarose and a heterogeneous mixture of smaller molecules called agaropectin. It forms the supporting structure in the cell walls of certain species of algae and is released on boiling. These algae are known as agarophytes, belonging to the Rhodophyta phylum. The processing of food-grade agar removes the agaropectin, and the commercial product is essentially pure agarose.
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.
A growth medium or culture medium is a solid, liquid, or semi-solid designed to support the growth of a population of microorganisms or cells via the process of cell proliferation or small plants like the moss Physcomitrella patens. Different types of media are used for growing different types of cells.
YEPD or yeast extract peptone dextrose, also often abbreviated as YPD, is a complete medium for yeast growth. It contains yeast extract, peptone, double-distilled water, and glucose (dextrose). It can be used as solid medium by including agar. The yeast extract will typically contain all the amino acids necessary for growth. By being a complete medium, YEPD cannot be used as a selection medium to test for auxotrophs. Instead, YEPD is used as a growth medium to grow yeast cultures.
Lysogeny broth (LB) is a nutritionally rich medium primarily used for the growth of bacteria. Its creator, Giuseppe Bertani, intended LB to stand for lysogeny broth, but LB has also come to colloquially mean Luria broth, Lennox broth, life broth or Luria–Bertani medium. The formula of the LB medium was published in 1951 in the first paper of Bertani on lysogeny. In this article he described the modified single-burst experiment and the isolation of the phages P1, P2, and P3. He had developed the LB medium to optimize Shigella growth and plaque formation.
Dermatophyte test medium (DTM) is a specialized agar used in medical mycology. It is based on Sabouraud's dextrose agar with added cycloheximide to inhibit saprotrophic growth, antibiotic to inhibit bacterial growth, and phenol red a pH indicator. The pH indicator is useful in distinguishing a dermatophyte fungus, which utilizes nitrogenous material for preferred metabolism, producing alkaline by-products, imparting a red color change to the medium. Typical saprotrophic fungi utilize carbohydrates in the medium producing acidic by-products and no red color change.
Buffered charcoal yeast extract (BCYE) agar is a selective growth medium used to culture or grow certain types of bacteria, particularly the Gram-negative species Legionella pneumophila. It has also been used for the laboratory diagnosis of Acanthamoeba keratitis, Francisella and Nocardia spp. It contains L-cysteine amino acid and ferric pyrophosphate that assist in the growth of Legionnaire's species. The charcoal within the medium acts as a detoxicant because it decomposes hydrogen peroxide which is toxic to the legionellae. The yeast extract in BCYE is the rich source of nutrients (vitamins, nitrogen, and carbon) that the bacteria depends on for growth. BCYE also has ACES buffer which maintains an optimal pH level for the bacteria to grow which is around 6.9. BCYE may be supplemented with antibiotics to select for legionellae, especially if screening an environmental or non-potable water specimen.
R2A 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.
Brain heart infusion (BHI) is a growth medium for growing microorganisms. It is a nutrient-rich medium, and can therefore be used to culture a variety of fastidious organisms. In particular, it has been used to culture streptococci, pneumococci and meningococci, which can be otherwise challenging to grow. BHI is made by combining an infusion from boiled bovine or porcine heart and brain with a variety of other nutrients. BHI broth is often used in food safety, water safety, and antibiotic sensitivity tests.
YM Agar and Broth, is a selective growth medium with low pH useful for cultivating yeasts, molds, or other acid-tolerant or acidophilic organisms, while deterring growth of most bacteria and other acid intolerant organisms. It is malt extract medium modified by the addition of yeast extract and peptone.
Nutrient agar is a general-purpose solid medium supporting growth of a wide range of non-fastidious organisms. It typically contains (mass/volume):
Sabouraud agar or Sabouraud dextrose agar (SDA) is a type of agar growth medium containing peptones. It is used to cultivate dermatophytes and other types of fungi, and can also grow filamentous bacteria such as Nocardia. It has utility for research and clinical care.
Hanseniaspora guilliermondii is a species of yeast in the family Saccharomycetaceae. In its anamorph form, it is called Kloeckera apis.
Lentilactobacillus hilgardii is a species of bacterium found in wine, dairy products, and wine musts.
The NYC medium or GC medium agar is used for isolating Gonococci.
Farrell's medium is a selective bacteriological medium for Brucella species which is prepared by the addition of six antibiotics to a basal bacteriological medium such as serum dextrose agar. In order to prepare 1 liter of the Farrell's medium, the following quantities are added to 1 liter of serum dextrose agar: polymyxin B sulfate, bacitracin, natamycin (50 mg), nalidixic acid (5 mg), nystatin, and vancomycin (20 mg). Vancomycin inhibits the growth of gram-positive bacteria on this medium, while nystatin inhibits the growth of fungi. Other antibiotics inhibit the growth of gram-negative bacteria other than Brucella species, thus favoring the exclusive growth of the latter in this medium.
In microbiology, the term isolation refers to the separation of a strain from a natural, mixed population of living microbes, as present in the environment, for example in water or soil, or from living beings with skin flora, oral flora or gut flora, in order to identify the microbe(s) of interest. Historically, the laboratory techniques of isolation first developed in the field of bacteriology and parasitology, before those in virology during the 20th century.
Keratinophyton durum is a keratinophilic fungus, that grows on keratin found in decomposing or shed animal hair and bird feathers. Various studies conducted in Canada, Japan, India, Spain, Poland, Ivory Coast and Iraq have isolated this fungus from decomposing animal hair and bird feathers using SDA and hair-bait technique. Presence of fungus in soil sediments and their ability to decompose hairs make them a potential human pathogen.
Mariannaea elegans an anamorphic fungus. It is mainly found on rotting wood and soil. M. elegans is not pathogenic to humans, animals, or plants.
Metarhizium granulomatis is a fungus in the family Clavicipitaceae associated with systemic mycosis in veiled chameleons. The genus Metarhizium is known to infect arthropods, and collectively are referred to green-spored asexual pathogenic fungi. This species grows near the roots of plants and has been reported as an agent of disease in captive veiled chameleons. The etymology of the species epithet, "granulomatis" refers to the ability of the fungus to cause granulomatous disease in susceptible reptiles.
