3-4: Transformation + Conjugation in E. coli Flashcards
Define Transformation
The process by which bacteria take up naked DNA from their surrounding medium and thus acquire new genes
What is different between Streptococci and E. coli in terms of willingness to transform?
Streptococci use transformation naturally, whereas E. coli only show transformation when “encouraged” to under lab conditions (made “competent”)
Describe the structure/layout of the pGLO plasmid
ori: origin of replication
araC: codes for a regulatory protein
gfp: codes for Green Fluorescent Protein
bla: codes for ß-lactamase, which digests the antibiotic ampicillin
Explain the importance of vectors in artificial transformation
If a gene of interest is simply inserted into a cell, it will not express it. Instead, it must be inserted into suitable carrier/vector, with the necessary transcription and translation signals
Explain the link between arabinose and controlling GFP production
Bacterial cells only produce enzymes to digest arabinose WHEN arabinose is present (similar to lac operon) - if arabinose metabolism genes are replaced with gene of interest, e.g., gfp, then this gene can be switched on or off by the presence/absence of arabinose
Define bacterial conjugation
The direct transfer of DNA from a donor to a recipient cell via direct contact of the cells
What are conjugative plasmids known as?
Sex/Fertility (F) plasmids
How does conjugation actually occur?
The F pilus draws the two cells together, allowing the membranes to fuse and form a “conjugation bridge,” one strand of the plasmid is nicked and it is transferred to the recipient cell; one strand is replicated in each cell, leaving both cells with a copy of the plasmid
What are the two types of conjugative pili?
Long, flexible pili (encoded by the F plasmid) form durable contacts in both liquid and solid media
Short, brittle pili (encoded by R plasmids) ONLY form durable contacts when cells are immobilised on solid media
