Microbial Growth

Question 1

what is the bacterial cell cycle?

Answer 1

the sequence of events from the formation of a new cell through the next cell division

Question 2

how do bacteria replicate?

Answer 2

through binary fission

Question 3

what are the 3 phases of the bacterial cell cycle?

Answer 3

1. period of growth after the cell is born
2. chromosome replication and partitioning
3. cytokenesis

Question 4

what are the 5 stages of binary fission?

Answer 4

1. cell at early phase of life cycle
2. chromosome replication; prep for division by enlarging cell wall, plasma membrane, and overall volume
3. septum grows inward as chromosomes move toward opposite ends of cell; distribute cytoplasmic components
4. septum synthesized completely through cell center, creating two separate cell chambers
5. division

Question 5

describe most bacterial chromosomes

Answer 5

singular, circular chromosome

Question 6

how many replication origins do bacteria have?

Answer 6

just one

Question 7

what is the single origin of replication in a bacterial cell?

Answer 7

site at which replication begins

Question 8

what is the terminus in bacterial cells?

Answer 8

site at which replication is terminated, located opposite of the origin

Question 9

what is the replisome of bacterial cells?

Answer 9

group of proteins needed for DNA synthesis

Question 10

in what direction does DNA synthesis proceed?

Answer 10

in BOTH directions from the origin of replication

Question 11

where do the origins of replication move to in microbial replication?

Answer 11

opposite ends of cell

Question 12

what is septation also known as?

Answer 12

cytokinesis

Question 13

when does septation begin?

Answer 13

when the z ring forms

Question 14

describe septation in terms of the Z ring and MinCD

Answer 14

MinCD is a protein that oscillates back and forth across the bacteral cell, and keep the Z ring from forming until the cell is long enough that it takes too much time to go from one end of the cell to another, thus allowing the Z ring to form one the cell is ready for septation

Question 15

what is septation?

Answer 15

formation of the cross wall between two daughter cells

Question 16

what are the 4 steps of septation?

Answer 16

1. selection of site for septum formation
2. assembly of Z ring
3. assembly of cell-wall synthesizing machinery
4. constriction of cell and septum formation

Question 17

what protein is the Z ring composed of?

Answer 17

FtsZ

Question 18

what part of the bacterial life cycle do a lot of antibiotics target?

Answer 18

cell growth and division

Question 19

what is important to take away from the super complex process of septation?

Answer 19

that you can attack steps along the way to treat infection

Question 20

when does Z ring formation occur?

Answer 20

after replication of genetic material

Question 21

is FtsZ the only protein involved in Z ring formation?

Answer 21

no there are others involved, but don’t worry about it

Question 22

what must be synthesized as cells divide?

Answer 22

peptidoglycan!!

Question 23

what is cellular growth?

Answer 23

increase in cellular constituents

Question 24

what 2 things could cellular growth result in?

Answer 24

1. increase in cell number

2. increase in cell size

Question 25

what does cellular growth refer to?

Answer 25

population growth rather than growth of individual cells

Question 26

when is the microbial growth curve observed?

Answer 26

when microorganisms are cultivated in batch culture

Question 27

how is the microbial growth curve plotted?

Answer 27

as the logarithm of cell number versus time

Question 28

what are the 5 distinct phases of the microbial growth curve?

Answer 28

1. lag phase 2. log phase 3. stationary phase 4. death phase 5. long-term stationary phase

Question 29

what happens in the lag phase of microbial growth curve?

Answer 29

cell is synthesizing new components

Question 30

give two reasons why the cell would need to synthesize new components in the lag phase of the microbial growth curve

Answer 30

1. to replenish spent material | 2. to adapt to new medium or other conditions

Question 31

how long is the lag phase?

Answer 31

varies in length, can be very short or even absent

Question 32

what is the log phase of the microbial growth curve also called?

Answer 32

exponential phase

Question 33

describe rate of growth in the log phase of the microbial growth curve

Answer 33

constant and maxmal

Question 34

describe the microbial population in the log phase of the microbial growth curve

Answer 34

uniform in terms of chemical and physical properties

Question 35

describe the stationary phase of the microbial growth curve

Answer 35

closed system population growth eventually ceases; total number of viable cells remains constant

Question 36

what cancels out during the stationary phase of the microbial growth curve?

Answer 36

cell death = cell growth

Question 37

what may happen to the population in the stationary phase of the microbial growth curve?

Answer 37

population may cease to divide, but remain metabolically active

Question 38

what are the 4 possible reasons for the stationary phase of the microbial growth curve?

Answer 38

1. nutrient limitation 2. limited oxygen availability 3. toxic waste accumulation 4. critical population density reached

Question 39

what is the stationary phase of the microbial growth curve also called?

Answer 39

holding pattern/plateau

Question 40

what is the death phase of the microbial growth curve?

Answer 40

when the number of viable cells declines exponentially, with cells dying at a constant rate

Question 41

what happens during the death phase of the microbial growth curve in terms of the environment?

Answer 41

detrimental environmental changes cause irreparable harm to the cells

Question 42

list and describe 2 hypotheses for why the death phase occurs

Answer 42

1. cells are viable but not culturable (VBNC): cells alive, but dormant, capable of new growth when conditions are right 2. programmed cell death: fraction of the population genetically programmed to die (commit suicide)

Question 43

what happens in the long-term stationary phase of the microbial growth curve?

Answer 43

bacterial population continually evolves

Question 44

what is the long-term stationary phase of the microbial growth curve marked by?

Answer 44

successive waves of genetically distinct variants

Question 45

what occurs during the long-term stationary phase of the microbial growth curve?

Answer 45

natural selection