Chapter 5 - PPT

Question 1

Binary fission:

Answer 1

cell division following enlargement of a cell to twice its minimum size 1 becomes 2, which becomes 4, which becomes 8, … Exponential; Logarithmic scale

Question 2

Doubling time

Answer 2

time required for microbial cells to double in number A.k.a. generation time E. coli: short doubling time, 20 min B. japonicum: long doubling time, 24 hours Function of the slope of the line of cells vs. time on log scale Chapter 5 II

Question 3

Divisome:

Answer 3

cell division apparatus FtsZ: forms ring around center of cel Fts (filamentous temperature-sensitive) proteins Essential for cell division in ZipA: anchor that connects FtsZ ring to cytoplasmic membrane FtsA: helps connect FtsZ ring to membrane and also recruits other divisome proteins

Question 4

Divisome complex and FtsZ ring Image

Answer 4

Question 5

Answer 5

Wall band and growth zone of Petidoglycan covered Cell

Question 6

Exponential growth:

Answer 6

growth of a microbial population in which cell numbers double within a specific time interval (doubling time)
When graphed on linear scale – curved line
When graphed on logarithmic scale – straight line
Slope of line indicates doubling time

Question 7

Doubling time graphs

Logorithmic and arathmatic

Answer 7

Question 8

Doubling time

Answer 8

(dt) of the exponentially growing population is
dt = t/n
t is the duration of exponential growth
n is the number of generations during the period of exponential growth

Question 9

Growth Rate

Answer 9

(v) is calculated as
v = 1/dt

Question 10

Graphs of Exponential growth

Mathamatics and graphs

Answer 10

Question 11

Batch Culture

Answer 11

a closed-system microbial culture of fixed volume

Question 12

Lag phase
Exponential phase
Stationary phase
Death phase

Answer 12

Question 13

Lag phase

Answer 13

Interval between when a culture is inoculated and when growth begins

Question 14

Exponential phase

Answer 14

Cells in this phase are typically the healthiest
Primary metabolites produced

Question 15

Stationary phase

Answer 15

Growth rate of population is zero
Either an essential nutrient is used up or product of the organism accumulated
Secondary metabolites are produced

Question 16

Death Phase

Answer 16

If incubation continues after cells reach stationary phase, the cells will eventually die?

Question 17

Continuous culture

Answer 17

an open-system microbial culture of fixed volume

Question 18

Chemostat

Answer 18

: most common type of continuous culture device
Extend exponential phase, prevent stationary/death
Both growth rate and population density of culture can be controlled independently and simultaneously
Dilution rate: rate at which fresh medium is pumped in and spent medium is pumped out

Question 19

Chemostat Graph

Answer 19

Question 20

Microscopic Counts

Answer 20

Question 21

Viable cell counts

Answer 21

(plate counts): measurement of living, reproducing population
Two main ways to perform plate counts:
Spread-plate method
Pour-plate method
To obtain the appropriate colony number, the sample to be counted should always be diluted

Question 22

The Great Plate Anomaly

Answer 22

evaluation of natural samples reveal far more organisms than those recoverable on/in media
Microscopic methods count dead cells whereas viable methods do not
Different organisms have vastly different requirements for growth
Media biased towards certain microbes
Majority of microorganisms are viable, but not culturable
Dormant state
Scout hypothesis

Question 23

Turbidity

Answer 23

(cloudiness) measurements are an indirect, rapid, and useful method of measuring microbial growth
Most often measured with a spectrophotometer
Measurement referred to as optical density (O.D.)

Question 24

Spectrophotometer

Answer 24

Question 25

Flow cytometer

Answer 25

Uses laser beams, fluorescent dyes, and computers Cells can be sorted while counted

Question 26

Temperature Graph Minimum Membrane gelling, transport processes so slow that growth cannot occur Enzymatic reactions occuring at increasingly rapid rates Optimum Enzymatic reactions occuring at maximal possible rate Maximum Protein denaturation; collapse of the cytoplasmic membrane; termal lysis

Answer 26

Question 27

Psychrophile:

Answer 27

–low temperature

Question 28

Mesophile:

Answer 28

midrange temperature

Question 29

Thermophile:

Answer 29

high temperature

Question 30

Hyperthermophile:

Answer 30

very high temperature

Question 31

Image Temperature Graphs

Answer 31

Question 32

Water activity (aw):

Answer 32

water availability; expressed in physical terms Defined as ratio of vapor pressure of air in equilibrium with a substance or solution to the vapor pressure of pure water

Question 33

Halophiles:

Answer 33

organisms that grow best at reduced water potential; have a specific requirement for NaCl

Question 34

Xerophiles

Answer 34

organisms able to grow in very dry environments