E.coli Lecture 1

Question 1

E.coli is a commensal bacterium. What does that mean?

Answer 1

Commensal means one species provides benefits for the host while the other gains nothing but isnt harmed as well

Question 2

What are some benfits of having E.coli?

Answer 2

consumption of oxygen (allows anaerobic bacteria to grow)
synthesis of Vitamin K and B
competition with pathogenic bacteria

Question 3

How is the genome of E.coli structured?

Answer 3

Core genome (all E.coli have it) and variable genome (only 1 E.coli has it)
Plasmids are part of the variable genome

Question 4

What is Horizontal Gene Transfere (HGT)?

Answer 4

Mediated by Mobile Genetic elements like conjugative plasmids and phages
or the DNA is shuffeld by Trnsposons

Question 5

How does the mechanism of HGT take place?

Answer 5

Donor cell has conjugative plasmid and conjugates part of their DNA to the recipient who integrates this DNA into their own genome

Question 6

How does HGT by phages work?

Answer 6

Upon infection phage DNA can be integrated into bacterial genome or be kept as plasmid.(lysogen)

Question 7

How are Multidrug resitances normaly transfered between bacteria?

Answer 7

They normaly reside on conjugative or mobilizable plasmids and are transfered that way.

Question 8

What are types of HGT in E.coli?

Answer 8

Conjugation
Mobilization
Lysogenization
Transduction
Satellites

Question 9

Process of Conjugation

Answer 9

Conjugative plasmid -> conjugation -> plasmid is duplicated

Question 10

Process of Mobilization

Answer 10

Conjugative plasmid+ mobilizable plasmid -> conjugative -> Both plasmids are duplicated

Question 11

Process of Lysogenization

Answer 11

Phage injects DNA -> DNA can be integrated or remain als plasmid (lysogen)

Question 12

Process of Transduction

Answer 12

First phage infection lyses cells and packs Host DNA in its capside -> upon reinfection of another bacteria this previous bacterial host DNA is integrated

Question 13

Process of Satellites

Answer 13

Previous phage infection has integrated DNA in host -> reinfection of another phage now makes new phages with this already present other phage DNA

Question 14

What bacterial strains are important and why?

Answer 14

K12 and B and BL21 and DH5a
K12 for biochemical genetics
B for phages
BL21 for protein purification (natural protease mutant)
DH5a for blue white screening