Escherichia coli required materials

Ames developed strains of bacteria that had carefully selected lethal mutations. In a test system the bacteria could survive only when its mutation had been corrected by experiencing another mutation caused by the tested material. This correction could be accomplished by causing a point mutation or frameshift mutations . Point mutations are base-pair substitutions, that is, a base change in DNA of at least one DNA base pair. In a reverse mutation test, this change in base pairs may occur at the site of the original mutation, or at a secondary site in the bacterial genome. Frameshift mutations are the addition or deletion of one or more base pairs in the DNA. Since amino acids are encoded by triplets of base pairs in sequence, any addition or deletion of 1 or 2 base pairs will dramatically alter the expressed protein from that point on. The Ames system employs strains of Salmonella typhimurium and Escherichia coli that require amino acids (histidine or tryptophan, respectively) to detect such reverse point and frameshift mutations. The reverse mutation allows the S. typhimurium or E. coli strains to restore the functional capability of the bacteria to be able to synthesize the specific amino acid on their own, independent of amino acid content in the medium. 

DNA polymerases perform essential roles in the replication and repair of genetic material. The DNA polymerases of several mesophiles have been extensively characterized, and the structural, biochemical, and kinetic properties of Escherichia coli, yeast, mammalian, and bacteriophage DNA polymerases have been the subject of numerous reviews. " Certain enzymes complement DNA polymerase activity with 3 - -5 -exonuclease (proofreading) activity and/or 5 - 3 -exonuclease activity, which typically reside in separate structural domains on the same polypeptide. To orchestrate DNA replication and repair, both eubacteria and eukaryotes possess multiple DNA polymerases, each with distinct properties, subunit compositions, and physiological roles. In vivo, DNA polymerases require the assistance of numerous accessory proteins to replicate and repair the genome (reviewed ). Based on amino acid sequence homology to E. coli enzymes, DNA polymerases have been classified into at least three distinct families Family A (Pol I-like), Family B (Pol Il-like), and Family C (Pol Ill-like). ... 

Succinic acid is one of the high-volume specialty chemicals. It is produced by the catalytic hydrogenation of petrochemical maleic acid or anhydride. However, due to cost reductions delivered via the production of succinic acid from the bacterial fermentation of carbohydrates, a large-volume commodity market could be realized. Presently, the bacterial strain used for succinic acid manufacturing is Escherichia coli. However, the requirement for lower costs is moving companies toward other microorganisms, such as Coryne-type bacteria and yeast. Succinic acid can be converted to 1,4-butanediol (EDO) and other products. It also serves as a raw material for diverse important chemicals, including polymers, polybutylene terephthalate, and polybutylene succinate. 

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