For M Sc II semester Dr Deepak V Vedpathak Associate Professor Department of Microbiology Fredrick Griffith Rajarshi Shahu Mahavidyalaya Autonomous Latur MS ID: 917562
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Transformation in Bacteria(For M. Sc. II semester)
Dr Deepak V. Vedpathak Associate Professor, Department of Microbiology. Fredrick GriffithRajarshi Shahu Mahavidyalaya (Autonomous),Latur (MS)
Dr DVV, LTR/2020
Slide2Transformation
In bacteria, DNA can be horizontally acquired through three main mechanisms: transformation, conjugation, and transduction.Transformation is the unidirectional transfer of exogenous DNA from environment into recipient cell through the cell membrane, resulting in its genetic alterationThe cells that have undergone transformation are called transformants. in 1928 Frederick Griffith reported an unknown transforming principleIn 1944 Oswald Avery and colleagues showed that DNA is the transforming principleNative bacterial chromosomal fragments, plasmids, bacteriophage DNA as well as genetically constructed chimeric molecules can be used for transformation.
Dr DVV, LTR/2020
Slide3Transformation Griffith
ExperimentDr DVV, LTR/2020
Slide4Transformation Oswald
Avery, Colin MacLeod and Maclyn McCarty ExperimentDr DVV, LTR/2020
Slide5Transformation Mapping
In mapping experiments using transformationDNA from a donor bacterial strain is extracted, purified, and broken into small fragments. This DNA is then added to recipient bacteria having a different genotype. If the donor DNA is taken up by a recipient cell and recombines with the homologous parts of the recipient’s chromosome, a recombinant chromosome is produced.
Dr DVV, LTR/2020
Slide6TransformationCompetence:
Ability of a bacterium to take up DNA segment from its environment. Competence may be Natural or artificially developed Natural competence: Neisseria and related bacteria: Express competence constitutively Bacillus subtilis and other bacteria: competence is gene regulated by producing competence factor
Dr DVV, LTR/2020
Slide7Transformation
Dr DVV, LTR/2020
Slide8Transformation
Dr DVV, LTR/2020Artificial competence: In non competent cells,. competence can be developed artificially through physical manipulations by chemical or physical treatments. Examples:
Escherichia coli ,
Salmonella typhimurium, many other bacteria as well as plant and animal cells
Widely used in genetic engineering
The methods for developing artificial competence are
The divalent cation method
Electroporation method
Polyethylene glycol method
Slide9Transformation
Dr DVV, LTR/2020
Slide10Transformation
Mechanism ofDr DVV, LTR/2020
Slide11Transformation
Transformation efficiency: The efficiency by which cells can take up extracellular DNA and express genes coded by it . It can be calculated by dividing the successful transformants by the amount of DNA used for transformation procedure. Colony Forming UnitsTransformation efficiency= ------------------------------------ DNA spread on the plate(µg)Transformation efficiency is depend on Competence Size of exogenous DNA Form of DNA –
dsDNA transported efficiently than
ssDNA
Damage to DNA
Dr DVV, LTR/2020
Slide12Transformation
Dr DVV, LTR/2020Thank you