Chapter 3

Question 1

Supercoiling of DNA

Answer 1

• E.	coli	chromosome	
– 4.64	Mbp	of	DNA	=	4,639,221	base	pairs	
– =1.58	mm	
• E.	coli	cell	
– 2	µm	in	length

Question 2

The E. coli chromosome

Answer 2

88%	of	genome	
is	coding	
• 20%	HGT	
• 4225	proteins,	
30%	of	proteins	
are	hypothe6cal	
• 70%	of	
transcrip6onal	
units	contain	
only	one	gene

Question 3

Plasmids

Answer 3

Extrachromosomal DNA that replicates
independently and has no extracellular form
• Thousands naturally occurring

Question 4

Plasmid characteris6cs

Answer 4

Copy number
– Low copy: 1-3
– High copy: ~100
• Cell-to-cell transfer

Question 5

Bacteriocins

Answer 5

• Proteins	that	kill	closely	related	species	or	
strains	
– Form	channels	
– Nucleases	
• Plasmid	encoded	
• E.	coli—colicins
• Y.	pes=s—pesticins