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The transformation efficiency is then calculated as the percentage of cells that express the fluorescent protein. [5] The number of viable cells in a preparation for a transformation reaction may range from 2×10 8 to 10 11; most common methods of E. coli preparation yield around 10 10 viable cells per reaction.
However, a mutant β-galactosidase derived from the M15 strain of E. coli has its N-terminal residues 11—41 deleted and this mutant, the ω-peptide, is unable to form a tetramer and is inactive. This mutant form of protein however may return fully to its active tetrameric state in the presence of an N-terminal fragment of the protein, the α ...
DH5-Alpha Cells are E. coli cells engineered by American biologist Douglas Hanahan to maximize transformation efficiency. They are defined by three [1] mutations: recA1, endA1 which help plasmid insertion and lacZΔM15 which enables blue white screening.
It was originally thought that Escherichia coli, a commonly used laboratory organism, was refractory to transformation. However, in 1970, Morton Mandel and Akiko Higa showed that E. coli may be induced to take up DNA from bacteriophage λ without the use of helper phage after treatment with calcium chloride solution. [6]
E. coli BL21(DE3) lacks a functional type I restriction-modification system, indicated by hsdS(r B − m B −). Specifically, both the restriction (hsdR) and modification (hsdM) domains are inactive. This enhances transformation efficiency since exogenously introduced unmethylated DNA remains untargeted by the restriction-modification system. [9]
Super Optimal Broth (SOB medium) is a nutrient-rich bacterial growth medium used for microbiological culture, generally of Escherichia coli.This nutrient-rich microbial broth contains peptides, amino acids, water soluble vitamins and glucose in a low-salt formulation.
Referred to as E. coli O157:H7 or Shiga toxin-producing E. coli (STEC), this strain of E. coli can be particularly dangerous and even life-threatening. The primary sources of STEC outbreaks are ...
Calcium chloride treatment is generally used for the transformation of E. coli and other bacteria. [11] It enhances plasmid DNA incorporation by the bacterial cell, promoting genetic transformation. Plasmid DNA can attach to LPS by being added to the cell solution together with CaCl 2. [12]