6-1: Cell Division

Question 1

How do most microbial cells divide

Answer 1

Binary fission

Question 2

How does binary fission work

Answer 2

DNA replicates, cell grows, cytoplasm divided equally, produces two identical daughter cells

Question 3

What happens after DNA replicates during binary fission

Answer 3

It is segregated to opposite sides of the cell

Question 4

What is the septum

Answer 4

Forms to separate cells during binary fission, pinches cells off

Question 5

What needs to be highly regulated/coordinated during cell division

Answer 5

Only happens at appropriate time (food available)
Chromosomes replicated well, each cell gets one copy
Septum forms at correct location
Coordinate nutritional status with DNA synthesis, cell envelope synthesis, division processes
Cell wall remains intact to prevent bursting

Question 6

DNA replication starts at specific site on chromosome called…

Answer 6

oriC

Question 7

What protein binds oriC to initiate replication

Answer 7

DnaA

Question 8

DNA is fully replicated, meaning?

Answer 8

Each strand of double-stranded chromosome acts as a template to produce a new strand

Question 9

What promotes the formation of the septum at the center of the cell

Answer 9

Z-ring formation - divisome

Question 10

What is generation time

Answer 10

Time to double your population

Question 11

How can generation time be shorter than the time it takes to replicate the chromosome?

Answer 11

In some bacteria (e.g. e coli), multiple DNA replication forks can be active at once
Multiple rounds of DNA replication at once

Question 12

How do multiple rounds of DNA replication at once work

Answer 12

OriC region starts being replicated again before the first fork is finished
All daughter cells receive a complete chromosome

Question 13

What are divisomes

Answer 13

Multi-protein complexes that help identify the center of the cell, build a septum, and separate the cell into two daughter cells

Question 14

Central protein of divisome? Its role?

Answer 14

FtsZ
Polymerizes to form ring around circumference of cell at midcell where division will occur
Constricts to help division occur

Question 15

Finding the midcell depends on…

Answer 15

Nucleoid occlusion - presence of the chromosome at the midcell prevents divisome from forming

FtsZ ring inhibitors concentrate at pole

Question 16

How do FtsZ ring inhibitors work

Answer 16

Cluster at cell pole and their lowest concentration are at the midcell, so FtsZ go there

Question 17

How does the e. coli min system work

Answer 17

MinD localized to poles, recruits MinC which inhibits FtsZ ring formation at poles. MinC concentration lowest at midcell

Question 18

What do autolysins do during cell wall growth

Answer 18

Break glycolytic bonds for insertion of new monomers

Question 19

What does bactoprenol do during cell wall growth

Answer 19

Bring peptidoglycan precursors across cytoplasmic membrane to remodel CW

Question 20

What do translgycosylases and transpeptidases do during cell wall growth

Answer 20

Transglycosylases form new bonds in sugar backbone

Transpeptidases form new peptide crosslinks

Question 21

How does cell wall growth work in most rod-shaped cell, what protein does this

Answer 21

MreB protein
New cell wall is added along the long axis of the cell

Question 22

What is an alternative to binary fission

Answer 22

Budding division, new cell grows from old by budding off from particular site of mother cell

Question 23

Where does budding usually occur

Answer 23

Long extensions called hyphae

Question 24

Multiple fission is

Answer 24

When hyphal filaments form multiple septa at once and break off into many cells