Lysogeny

broth Broth, also known as bouillon (), is a savory liquid made of water in which meat, fish, or vegetables have been simmered for a short period of time. It can be eaten alone, but it is most commonly used to prepare other dishes, such as soups ...

(LB) is a nutritionally rich

medium Medium may refer to: Aircraft *Medium bomber, a class of warplane * Tecma Medium, a French hang glider design Arts, entertainment, and media Films * ''The Medium'' (1921 film), a German silent film * ''The Medium'' (1951 film), a film vers ...

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 ''Shigella'' is a genus of bacteria that is Gram negative, facultatively anaerobic, non–spore-forming, nonmotile, rod shaped, and is genetically nested within ''Escherichia''. The genus is named after Kiyoshi Shiga, who discovered it in 1 ...

'' growth and plaque formation. LB medium formulations have been an industry standard for the cultivation of ''

Escherichia coli ''Escherichia coli'' ( )Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. is a gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Escherichia'' that is commonly fo ...

'' as far back as the 1950s. These media have been widely used in

molecular microbiology Molecular biology is a branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. Though cells and other microsco ...

applications for the preparation of

plasmid A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria and ...

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

and recombinant proteins. It continues to be one of the most common media used for maintaining and cultivating laboratory recombinant strains of ''Escherichia coli''. For physiological studies however, the use of LB medium is discouraged. There are several common formulations of LB. Although they are different, they generally share a somewhat similar composition of ingredients used to promote growth, including the following: *

Peptides Peptides are short chains of amino acids linked by peptide bonds. A polypeptide is a longer, continuous, unbranched peptide chain. Polypeptides that have a molecular mass of 10,000 Dalton (unit), Da or more are called proteins. Chains of fewer t ...

and

casein Casein ( , from Latin ''caseus'' "cheese") is a family of related phosphoproteins (CSN1S1, αS1, aS2, CSN2, β, K-casein, κ) that are commonly found in mammalian milk, comprising about 80% of the proteins in cow's milk and between 20% and 60% of ...

peptones Peptides are short chains of amino acids linked by peptide bonds. A polypeptide is a longer, continuous, unbranched peptide chain. Polypeptides that have a molecular mass of 10,000 Da or more are called proteins. Chains of fewer than twenty am ...

Vitamins Vitamins are organic molecules (or a set of closely related molecules called vitamers) that are essential to an organism in small quantities for proper metabolic function. Essential nutrients cannot be synthesized in the organism in suff ...

(including B vitamins) * Trace elements (e.g. nitrogen, sulfur, magnesium) * Minerals Sodium ions for transport and osmotic balance are provided by

sodium chloride Sodium chloride , commonly known as Salt#Edible salt, edible salt, is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. It is transparent or translucent, brittle, hygroscopic, and occurs a ...

. Tryptone is used to provide essential

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...

s such as peptides and peptones to the growing bacteria, while the

yeast extract Yeast extracts consist of the cell contents of yeast without the cell walls; they are used as food additives or flavorings, or as nutrients for bacterial culture Growing media, media. They are often used to create savoury flavors and umami tast ...

is used to provide a plethora of

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

s helpful for bacterial growth. These compounds include vitamins and certain trace elements. In his original 1951 paper, Bertani used 10 grams of NaCl and 1 gram of glucose per 1 L of solution; Luria in his "L broth" of 1957 copied Bertani's original recipe exactly. Recipes published later have typically left out the glucose.

Formula

The formulations generally differ in the amount of sodium chloride, thus providing selection of the appropriate osmotic conditions for the particular bacterial strain and desired culture conditions. The low salt formulations, Lennox and Luria, are ideal for cultures requiring salt-sensitive antibiotics. * LB (Miller) (10 g/L NaCl) * LB (Lennox) (5 g/L NaCl) * LB (Luria) (0.5 g/L NaCl)

Adjusting the pH

Prior to autoclaving, some laboratories adjust the pH of LB to 7.5 or 8 with sodium hydroxide. However, sodium hydroxide does not provide any buffering capacity to the media, and this results in rapid changes to the pH during bacteria cultivation. To get around this some laboratories prefer to adjust the pH with 5–10 mmol/L

TRIS Tris, or tris(hydroxymethyl)aminomethane, or known during medical use as tromethamine or THAM, is an organic compound with the formula (HOCH2)3CNH2. It is extensively used in biochemistry and molecular biology as a component of buffer solutions ...

buffer, diluted from 1 mol/L TRIS stock at the desired pH. However, it is not absolutely necessary to adjust the pH for most situations. Some laboratories adjust the pH to 7.0 merely as a precaution.

References

{{Growth media Microbiological media

Formula

Adjusting the pH

See also

References