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Lecture 23

MICRB316 Lecture Notes - Lecture 23: Rolling Circle Replication, Antimicrobial Resistance, Plasmid


Department
Microbiology (Biological Sciences)
Course Code
MICRB316
Professor
Jonathan Dennis
Lecture
23

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Plasmids
How do plasmids increase bacterial adaptability>
1. If a gene moves onto a plasmid, its copy # rises per bacterium therefore the gene
pool is increased
2. Then, the overall mutation rate increases, and more gene variations are possible
3. Genes on self-transmissible or mobilizable plasmids have an increased chance
of spreading between bacteria
Eg. Into a new host with different capabilities- survival of the plasmids- intrinsic
antibiotic resistant increases the chances of survival in a host.
(higher intrinsic antibiotic resistance). Some new plasmids can replicate on their
own immediately after entry into new host. No need for chromosome integration.
Immediate gene expression.
Transformation: DNA has to be inserted into the chromosome, genes need to be
inserted into a promoter, then you get adaptive advantage. For plasmids, they
bring their whole machinery over. They don’t need to integrate. They are ready to
go when they go into a new cell. Plasmids are like mini genomes coming over.
Narrow host range vs. broad host range- some can transfer well, some have
narrow range. A lot can replicate in both G+ and G-. Their promoters are well
recognized by different kinds of bacteria. Maybe they have multiple replication
gene sets that work on different bacteria- these are scary! They can go around
different kinds of bacteria.
4. Plasmids serve as carriers of other mobile genetic elements (insertion sequences
(ISs- no selective marker, just jump around), transposons (Tns- have a selecting
marker), phage- can also move to new host when they are integrated into
plasmids. Other genes can go into the plasmids.
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%2 2
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