Lecture 5

Question 1

Growth

Answer 1

Increase in cell number
Growth = reproduction

Question 2

Population

Answer 2

Total cells from one microbe

Question 3

Applications of cell division

Answer 3

Infectious diseases and food preservation

Question 4

Binary fission

Answer 4

Division of one fell into two
Elongation to septum formation
Generation time typically 30 min to 6 hours

Question 5

Generation time is affected by

Answer 5

Environmental factors (nutrient availability and temperature) and genetic factors (particular to different microbial species)

Question 6

Divisome

Answer 6

Directs cell division in prokaryotes
Embedded in cytoplasmic membrane
Comprises of Fts (filamenting temperature-sensitive) proteins

Question 7

FtsZ

Answer 7

Forms a ring around the center of the dividing cell
In bacteria and archaea
Relates to tubulin

Question 8

ZipA

Answer 8

Connects to FtsZ ring to the cytoplasmic membrane
The anchor

Question 9

FtsA

Answer 9

Attracts other Fts protein to the divisome
The recruiter

Question 10

FtsI

Answer 10

Peptidoglycan synthesis
- implications for drug design (new antibiotics)

Question 11

MreB protein

Answer 11

Form cellular cytoskeleton
Absent in coccoid bacteria
Present in rod-shapes bacteria (if it’s inactive they become coccoid)

Question 12

Exponential growth

Answer 12

Cells double each generation
Rate of cell production increases each generation
Healthiest state of cells for study
App. Standards for bacterial counts in food

Question 13

Microbial growth cycle

Answer 13

Lag phase, exponential phase, stationary phase, and death phase

Question 14

Lag phase

Answer 14

Growth rate= positive (low)
Recovery phase from previous conditions

Question 15

Stationary phase

Answer 15

Growth rate = zero
Nutrient depletion and waste accumulation

Question 16

Cryptic growth

Answer 16

Few cells still dividing
Few cells dying
Average of two makes stationary phase

Question 17

Death phase

Answer 17

Growth rate = negative (cell death)

Question 18

Continuous culture

Answer 18

Chemostat- constant conditions over time
Controls- dilution rate and nutrient concentration
Applications- ecology and physiology

Question 19

Microscopic counts

Answer 19

Cell counts
Adv: simple method
Dis: counts live and dead cells & difficulties with low cell numbers and motile cells

Question 20

Viable counts

Answer 20

Plate counts
Adv: high sensitivity and counts viable cells
Dis: possible errors (plating consistencies, incubation length, cell “clumps”

Question 21

Turbidimetric methods

Answer 21

Cell mass -> cell number
Adv: simple method & non-destructive
Dis: possible errors, cell clumps and films

Question 22

Cardinal temperatures

Answer 22

Minimum (no growth), optimal (fastest growth), maximum (cell death)

Question 23

Extremophiles

Answer 23

Live in very cold or very hot environments
- deep ocean, glaciers, polar regions
- hot springs, surface soils, and water

Question 24

Psychrophiles

Answer 24

Optimal temperature <15C
Typical slow growing
“Pockets” of water
Ex. Snow algae and seaice diatoms
Molecular adaptations:
- cytoplasmic membrane (high in unsaturated/short-chain FAs and fluidity at low temperature)
- cyroprotectants (“cold-shock” proteins, like anti-freeze for the cell)

Question 25

Life in the heat

Answer 25

Optimal temperature:
- >45C thermophiles
- > 80C hyperthermophiles
Ex. Boiling springs bacteria, hot spring Cyanobacteria, and hydrothermal vent microbes
Molecular adaptations:
- cytoplasmic membrane (high saturated FAs and stability at high temps)
Heat protectants (heat shock proteins through more ionic bonds)

Question 26

Polymerase chain reaction

Answer 26

cyclical heating of DNA to 94C and requires a heat-resistant polymerase

Question 27

Taq polymerase

Answer 27

Thermus aquaticus and hot spring bacterium

Question 28

Acidophiles

Answer 28

optimal growth < pH 5.5

Question 29

Alkaliphiles

Answer 29

optimal growth > pH 8