Deck 7: Microbial Growth

Question 1

Which of the following is a reason for the occurrence of a lag phase in a bacterial growth curve?

A) The cells may be old and depleted of ATP, essential cofactors, and ribosomes that must be synthesized before growth can begin.
B) The medium may be different from the previous growth medium so that the cells must synthesize new enzymes to use different nutrients.
C) The organisms may have been injured and require time to recover.
D) All of these are potential reasons.

Answer 1

D

Question 2

During the lag phase of microbial growth, the cells are metabolically inactive.

Answer 2

False

Question 3

The actin-like protein that seems to be involved in determining cell shape is

A) MreB.
B) ActA.
C) SpnC.
D) FtsZ.

Answer 3

A

Question 4

Microorganisms are most nearly uniform in terms of chemical and physiological properties during __________ phase.

A) lag
B) exponential
C) stationary
D) decline

Question 5

The cell wall of bacteria constrains the ___________ _________ that results from the osmolarity of the cytoplasmic contents.

Question 6

The length of the lag phase of growth can vary depending on

A) the condition of the microorganisms.
B) the nature of the growth medium.
C) the temperature.
D) all of the choices

Question 7

The process of forming a cross wall between two daughter cells is known as

A) replication
B) septation
C) sporulation
D) mitosis

Question 8

Which of the following is the correct order for binary fission?

A) a septum forms at midcell, the cell elongates, replicates its chromosome, and separates the chromosome into the two parts of the cell
B) the cell elongates, a septum forms at midcell, the cell replicates its chromosome, and separates the chromosome into the two parts of the cell
C) the cell elongates, replicates its chromosome, and separates the chromosome into the two parts of the cell, and a septum forms at midcell
D) none of the above

Question 9

During cytokinesis, a critical step in septation is the assembly of the

A) replisome.
B) spindle body.
C) Z ring.
D) cytoskeletal spiral.

Question 10

The purpose of the penicillin binding proteins is to link phospholipids together in the cellular membrane.

Question 11

Given a log phase bacterial culture with 1 x 10⁶ cells per ml and a generation time of 30 minutes, how long does it take the culture to reach a density of 6.4 $\times$ 10⁷ cells per ml?

A) 1 hour
B) 2 hours
C) 3 hours
D) 4 hours

Question 12

When a young, vigorously growing culture of bacteria is transferred to fresh medium of the same composition, the lag phase is usually short or absent.

Question 13

Cells may enter stationary phase because of

A) the depletion of an essential nutrient.
B) a lack of available oxygen.
C) the accumulation of toxic waste products.
D) all of the choices

Question 14

Most bacterial and archaeal cells divide by

A) mitosis
B) meiosis
C) binary fission
D) all of the above

Question 15

All bacterial and archaeal cells are diploid.

Question 16

A culture in a closed vessel to which no additional medium is added and from which no waste products are removed is called a __________ culture.

A) continuous
B) batch
C) fed-batch
D) semicontinuous

Question 17

The limitation on microbial growth rate at high nutrient levels is

A) the rate of protein synthesis.
B) the rate of DNA replication.
C) the saturation of the transport proteins for nutrient uptake.
D) all of the choices.

Question 18

The __________ is a group of proteins needed for DNA synthesis that assembles at the origin of replication.

A) septum
B) replisome
C) prospore
D) none of the above

Question 19

The site at which replication of DNA starts in bacterial cells is known as the __________ of ___________.

Question 20

The total number of viable microorganisms remains constant in stationary phase because

A) there is a balance between cell division and cell death.
B) there is a cessation of cell division even though the cells may remain metabolically active.
C) either there is a balance between cell division and cell death or there is a cessation of cell division even though the cells may remain metabolically active.
D) none of the choices

Question 21

At 4:00 p.m. a closed flask of sterile broth is inoculated with 10,000 cells. The lag phase lasts 1 hour. At 9:00 p.m. the log phase culture has population of 65 million cells. The approximate number of generations that has occurred is

A) 5.
B) 13.
C) 21.
D) 27.

Question 22

A culture system with constant environmental conditions maintained through continual provision of nutrient and removal of wastes is called __________ culture system.

A) continuous
B) batch
C) fed-batch
D) semicontinuous

Question 23

The growth rate of a given species of microorganism is dependent on the composition of the medium in which it is grown.

Question 24

One of the major advantages of a continuous culture system is that the cells can be maintained in the exponential growth phase for extended periods of time.

Question 25

Which of these methods can be used to determine the number of viable microorganisms in a sample?

A) light scattering in a spectrophotometer
B) measuring total cell mass
C) measuring colony forming units per ml
D) counting a known volume of cells in a hemocytometer

Question 26

Which of the following can be used to estimate the number of microorganisms in a culture?

A) direct counts of microbial cells
B) counts of viable cells using colony growth procedures
C) measurements of microbial biomass
D) all of the choices

Question 27

Organisms that grow well at 0 $\degree$ C and have optimum growth temperatures of 15 $\degree$ C or lower are called

A) psychrotrophs.
B) psychrophiles.
C) frigiphiles.
D) mesophiles.

Question 28

An open system in which the growth rate is maintained by the removal and addition of media at such a rate as to maintain a constant cell density is called a

A) manostat.
B) chemostat.
C) turbidostat.
D) culturostat.

Question 29

Organisms that do not require oxygen for growth but grow better in its presence are called

A) facultative anaerobes.
B) microaerophiles.
C) aerotolerant.
D) anoxygenic.

Question 30

Which of the following is considered a cardinal growth temperature?

A) the minimum temperature
B) the maximum temperature
C) the optimum temperature
D) All of these are considered cardinal growth temperatures.

Question 31

At 4:00 p.m. a closed flask of sterile broth is inoculated with 10,000 cells. The lag phase lasts 1 hour. At 9:00 p.m. the culture enters stationary phase with a population of 65 million cells. At what time is the population half maximal?

A) 6:30 p.m
B) 7:20 p.m
C) 8:20 p.m
D) 8:40 p.m

Question 32

An open system in which the growth rate is maintained by adding a nutrient (present in limiting quantities) at the same rate that medium containing microorganisms is removed is called

A) manostat.
B) chemostat.
C) turbidostat.
D) culturostat.

Question 33

When a young, vigorously growing culture of bacteria is transferred to fresh medium of different composition, the lag phase is usually short or absent.

Question 34

The __________ __________ is the length of time it takes for a population of microorganisms to double in number.

Question 35

Growth is said to be __________ when all cellular components are synthesized at constant rates relative to one another.

Question 36

Organisms that grow at 0 $\degree$ C and have a maximum growth temperature of 35 $\degree$ C are called

A) psychrotrophs.
B) psychrophiles.
C) frigiphiles.
D) mesophiles.

Question 37

In a continuous culture system, the rate at which media is added and removed is called the __________ rate.

A) dilution
B) chemostatic
C) pass-through
D) flow-through

Question 38

Microbial __________ is an increase in cell constituents that may or may not be accompanied by an increase in cell number.

Question 39

If all cell components are synthesized at constant rates relative to one another, the culture is said to be in __________ growth; however, if the rates of synthesis of some components change relative to the rates of synthesis of other components, the culture is said to be in __________ growth.

Question 40

At 4:00 p.m. a closed flask of sterile broth is inoculated with 10,000 cells. The lag phase lasts 1 hour. At 9:00 p.m. the log phase culture has a population of 65 million cells. The mean generation time is approximately

A) 10 minutes.
B) 20 minutes.
C) 30 minutes.
D) 40 minutes.

Question 41

Organisms that have their optimum growth pH between 8.5 and 11.5 are called __________.

Question 42

Organisms that require increased pressure for optimum growth are called

A) barotolerant.
B) osmotolerant.
C) barophilic.
D) osmophilic.

Question 43

Organisms that are damaged by the normal atmospheric levels of oxygen (20%) but require oxygen at levels of 2-10% for growth are called

A) facultative anaerobes.
B) microaerophiles.
C) aerotolerant.
D) anoxygenic.

Question 44

Organisms that require high levels of sodium chloride in order to grow are called __________ organisms.

Question 45

Organisms that can grow in habitats with low water activity by maintaining a high internal salt concentration are called __________ organisms.

Question 46

Organisms that grow in the mud under relatively nonturbulent bodies of water are likely to be

A) obligate aerobes.
B) thermophilic.
C) barophilic.
D) anaerobes.

Question 47

When a microorganism is placed in a(n) __________ solution, water will enter into the cell and cause it to burst unless something is done to prevent this.

A) hypotonic
B) isotonic
C) hypertonic
D) osmotonic

Question 48

Membranes of thermophilic bacteria are stabilized by phospholipids with

A) fatty acids that tend to be more saturated.
B) fatty acids that have lower molecular weights.
C) fatty acids that have more double bonds.
D) all of the choices

Question 49

Membranes of some thermophilic Archaea are stabilized by ether linked phospholipids.

Question 50

The membranes of psychrophilic bacteria have relatively high levels of __________ fatty acids, which allow them to remain semi-fluid at cold temperatures.

A) saturated
B) unsaturated
C) sterol
D) aromatic

Question 51

Organisms that are not drastically affected by increased pressure are called

A) barotolerant.
B) osmotolerant.
C) barophilic.
D) osmophilic.

Question 52

DNA of thermophiles is stabilized by binding of special nucleoid-associated proteins.

Question 53

Organisms that have their optimum growth pH between 0.0 and 5.5 are called __________.

Question 54

Obligate anaerobes are usually poisoned by molecular oxygen but may grow in aerobic habitats if associated with facultative anaerobes that use up all available oxygen.

Question 55

Organisms that ignore oxygen and grow equally well in its presence or absence are called

A) facultative anaerobes.
B) microaerophiles.
C) aerotolerant.
D) anoxygenic.

Question 56

Organisms that grow near deep-sea volcanic vents are likely to be

A) psychrophilic.
B) psychrotrophic.
C) mesophilic.
D) thermophilic.

Question 57

The primary mechanism by which DNA is damaged by ultraviolet radiation involves the formation of thymine dimers.

Question 58

Most microorganisms maintain their internal pH

A) near neutral (pH 7).
B) near their optimum growth pH.
C) slightly acidic (pH 4-6).
D) slightly alkaline (pH 8-10).

Question 59

Organisms that grow near deep-sea volcanic vents are likely to be

A) alkylophilic.
B) acidophilic.
C) barophilic or barotolerant.
D) picrophilic.

Question 60

Organisms that have their optimum growth pH between 5.5 and 8.0 are called __________.

Question 61

Quorum sensing in Gram-positive bacteria generally involves the use of ____________ as the external signaling molecules.

Question 62

Organisms with growth temperature maxima between 85 and 113 $\degree$ C are referred to as __________.

Question 63

A common type of autoinducer found in gram-negative bacteria are acyl homoserine lactones (AHL).

Question 64

Quorum sensing

A) is a phenomenon in which bacteria monitor their own population density.
B) depends on the sensing of signal protein molecules.
C) plays an important role in formation of biofilms by Pseudomonas aeruginosa.
D) all of the choices

Question 65

Organisms that grow best at pH levels above 10 are called __________ __________.

Question 66

Many microbes that live in environments where there is high exposure to light use _______________ to provide protection from photoxidation by singlet oxygen.

Question 67

A microbial environment containing high nutrient concentrations is called an oligotrophic environment.

Question 68

Complex microbial communities that grow tightly adhered to surfaces are called __________.