Mutagenesis A Conventional Tool for Strain Improvement
Mutations result from a physical change to the DNA of a cell, such as deletion, insertion, duplication, inversion and translocation of a piece of DNA, or a change in the number of copies of an entire gene or chromosome.
The subjection of microorganisms to repeated rounds of mutagenesis followed by suitable selection and screening of the survivors, has been a very effective tool in improving many industrial microorganisms. As mutants can arise naturally or be induced, they are considered to be the product of natural events. Consequently, there are fewer problems in gaining approval from the regulatory authorities than when recombinant DNA technology is used to develop an industrial microorganism. #mutragenesis #strain #method #microbiology #conventional #structure
Spontaneous mutation rates are low. The mutation rate can be greatly increased by using mutagens.
Physical mutagens include ultraviolet, g and X radiation; and chemical mutagens are compounds such as ethane methane sulphonate (EMS), nitroso methyl guanidine (NTG), nitrous acid and acridine mustards.
Mutants are formed when the mutagens induce modifications of the base sequences of DNA that result in basepair substitutions, frame-shift mutations or large deletions that go unrepaired.
Mutagenesis methods generally have rather limited use as they primarily achieve either loss of an undesirable characteristic or increasing production of a product, due to impairment of a control mechanism.
These traditional methods have been successfully employed in removing the yellow colour of early penicillin preparations caused by chrysogenin, a yellow pigment produced by Penicillium chrysogenum.
Mutagenesis programmes have also been highly effective in increasing the yield of penicillin in industrial strains of the same organism. Other notable examples of impairment of control processes, resulting in greater product yields, are seen in several microorganisms used for amino acid production.
29 сен 2024
