Chapter 5 Lec. 1

Question 1

cell growth and binary fission

Answer 1

Growth: increase in the number of cells.

Binary fission: cell division following enlargement.

Question 2

Microbial growth and cell division

Answer 2

Increase in mass.
Increase in cell numbers
-mitosis in most eukaryotes
-budding in yeasts

Question 3

Divison strategies: bacteria and archaea

Answer 3

Haploid only.
Asexual binary fission.
All calls must replicate and segregate genome prior to division.

Question 4

Steps in binary fission

Answer 4

Chromosome replication. 
Chromosome attachment to cell membrane. 
Chromosome segregation. 
Septum formation
-Inward movement of cell wall and cell membrane dividing daughter cells. 
Wall elongation.

Question 5

Bacterial chromosomal replication

Answer 5

Semiconservative
-Results in one new and one parental strand.
E. coli
-Bidirectionally from single origin
-Initiates replication.
-controls frequency of initiation events.
-segregates replicated chromosomes to daughter cells.

Question 6

Septation

Answer 6

Formation of cross walls between daughter cells.
Several steps:
-selection of site for septum formation.
-assembly of z ring.
-linkage of z ring to plasma membrane.
-assembly of cell wall synthesizing machinery.
-construction of cell and septum formation.

Question 7

Fts proteins and cell division

Answer 7

Fts (filamentous temperature sensitive)
-essential for cell division in prokaryotes.
Found among bacteria and archaea.

Question 8

Fts and cell division: FtsA, FtsZ and ZipA

Answer 8

Interact to form division apparatus (divisome).
FtsZ- attaches at center and forms ring.
FtsA- connects FtsZ to membrane and recruits other proteins.
ZipA- anchors FtsZ to cytoplasmic membrane.

Question 9

MreB and cell morphology 1

Answer 9

Prokaryotes contain a cell cytoskeleton.
MreB: major shape determining factor in prokaryotes:
-forms simple cytoskeleton in bacteria and archaea.
-localizes synthesis of new peptidoglycan and other cell wall components to specific locations

Question 10

Peptidoglycan synthesis and cell division

Answer 10

Production of new cell wall material and major feature of cell division.

• In cocci: grow in different directions.
• In rod shaped cells: occur at multiple points.

Question 11

Peptidoglycan synthesis and cell division: Before cell division

Answer 11

Before cell division can occur, cell wall synthesis must occur.
Preexisting peptidoglycan needs to be severed to allow new peptidoglycan to form.

Question 12

Peptidoglycan synthesis and cell division: Start of cell division

Answer 12

Beginning at FtsZ ring, small openings in wall are created by autolysins.
New cell material added across openings.
Wall band: junction between new and old peptidoglycan.

Question 13

Peptidoglycan growth

Answer 13

1. In cytoplasm uridine diphosphate attaches to NAM and NAG.
2. NAM-UDP attached to NAG and bacterprenol
3. Autolysins degrade peptidoglycan as new units are added.

Question 14

Bactoprenol

Answer 14

Lipid carrier molecule that plays major role in insertion of peptidoglycan precursors

Question 15

Glycolases

Answer 15

Enzymes that interact with bactoprenol to:

-insert cell wall precursors into growing points of cell wall.

Question 16

Transpeptidation

Answer 16

Final step in cell wall synthesis:

-Forms the peptide cross-links between muramic acid residues in adjacent gycan chains.

Question 17

Exponential growth

Answer 17

Most bacteria have shorter generation times than eukaryotic microbes.
Generation time dependent on growth medium and incubation conditions.

One cell splits into two (a generation) and so on- 1-2, 2-4, 4-8…

Generation time: time required for the population to double.

Question 18

Exponential growth: Colony growth

Answer 18

Growth of colony continues until one of things occurs:

• Nutrients depleted
• water depleted
• space depletion
• waste builds and poisons cells

Question 19

Exponential growth: Growth curve

Answer 19

Growth curve plotted by:

• Growing one species in broth at set temperature
• measuring number of bacteria at different time points.

Question 20

Mathematics of exponential growth

Answer 20

Relationship exists between initial number of cells in culture and number after a period of exponential growth.
N=N02^n