L4.2 Plasmids Flashcards
Methods of plasmid transfer
Conjugation
Transduction
Transformation
What happens in conjugation
the donor F+ cell form a bridge or pilus to attache to the recipient F- cell
Are all plasmids conjugative?
No
conjugative plasmids contains TRA gene (trasnfer gene)
Direct contact, transfers DNA strand, attachment of pilus/pili
Conjugation
Happens between virus and bacteria. Incorporates the bacterial chromosomal DNA into a virus particle. Virus will transfer it to a new DNA of recipient.
Transduction
Involves a dead donor cell leaving a fragment of DNA
Transformation
Trait of the plasmid
ColE1
bacteriocin kills E.coli
Tol
degradation of toluene and benzoic acid
Ti
Tumor initiation in plants
pJP4
2,4-D (dichlorophenoxyacetic acid) degradation
pSym
nodulation on roots of legume
SCP1
antibiotic methylenomycin biosynthesis
RK2
resistance to ampicillin, tetracycline and kanamycin
Types of bacterial plasmids
Fertility (F) plasmids
- has tra genes, conjudation, has pilus for cell-cell interaction
Resistance (R) plasmids
antibiotic resistant gene, R-factors, large
COL-plasmids
codes for colicines a type of bacteriocin that can kill bacterial cells
Degradative plasmids
digestion of chemicals, toulene
Virulence plasmids
virulence factors
Enumerate all the types of bacterial plasmids
Fertility
Resistance
COL
Degradative
Virulence
How is conformation of plasmid DNA seen?
through agarose gel and relative migration
Observed for native DNA conformation in vivo, extra twist, migrate faster
- desired conformation for isolating plasmid DNA
Supercoiled or covalently closed circular
DNA is intact but no supercoils
Relaxed circular
occurs due to excessive alkaline lysis, compacted plasmid form
single stranded, the fastest to migrate
supercoiled denatured
topoisomerases cut a portion of the supercoiled DNA to gain access for replication.
slowest conformation in the agarose gel
Nicked open circular
