Microbiology ch07 Microbial Growth
The growth rate constant, k, has units of _______.
1/hr
How many generations does it take for a single bacterial cell to become 256?
8
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
A
Mannitol salt agar (MSA) only allows the growth of halophiles (salt-loving microbes). Among the halophiles, mannitol fermenters release acid that turns the pH indicator yellow; mannitol nonfermenters leave the medium red. Onto MSA you inoculate a halophilic mannitol nonfermenter and a nonhalophilic mannitol nonfermenter. Here the medium acts as a __________ medium. A. selective B. differential C. selective and differential D. enrichment
A
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
A
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)
A
Organisms that are not drastically affected by increased pressure are called A. barotolerant. B. osmotolerant. C. barophilic. D. osmophilic.
A
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.
A
Organisms that grow at 0C and have a maximum growth temperature of 35C are called A. psychrotrophs. B. psychrophiles. C. frigiphiles. D. mesophiles.
A
The actin-like protein that seems to be involved in determining cell shape is A. MreB. B. ActA. C. SpnC. D. FtsZ.
A
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
A
Turbidity of a culture is typically measured by ___.
Absorbance
Microbes that grow best as pH below 5 are termed ___.
Acidophiles
Microbes that grow best as pH values above 8 are termed ___.
Alkaliphiles
The cloudiness of a broth culture that is indicative of microbial cells is called ___ and it can be measured using a spectrophotometer.
Turbidity
Organisms that have their optimum growth pH between 0.0 and 5.5 are called __________.
acidophiles
Organisms that have their optimum growth pH between 8.5 and 11.5 are called __________.
alkaliphiles
Growth is said to be __________ when all cellular components are synthesized at constant rates relative to one another.
balanced
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.
balanced, unbalanced
Complex microbial communities that grow tightly adhered to surfaces are called __________.
biofilms
Many microbes that live in environments where there is high exposure to light use _______________ to provide protection from photoxidation by singlet oxygen
carotenoids
Macroscopically visible growths or clusters of microorganisms on solid media are called __________.
colonies
What is the correct description of the process known as division of the cytoplasm into the daughter cells?
cytokinesis
Colonies grow most rapidly at the __________ where oxygen and nutrients are readily available; however, they grow less rapidly at the __________ where these materials have been depleted.
edge, center
The negative logarithm of the hydrogen ion concentration of a solution is its ___.
pH
Endocarditis occurs when bacteria infect the bloodstream and attach themselves to the inner lining of the heart or a defective heart valve. These bacteria are ______.
sessile
In the membrane filter technique of direct enumeration, a water sample is filtered and then ___.
stained
All fastidious microorganisms require which of the following for growth? A. Oxygen. B. Temperatures near normal for the human body. C. Extra nutrients (such as whole blood). D. Iron.
C
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.
C
Organisms that require increased pressure for optimum growth are called A. barotolerant. B. osmotolerant. C. barophilic. D. osmophilic.
C
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.
C
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.
C
T/F When a young, vigorously growing culture of bacteria is transferred to fresh medium of different composition, the lag phase is usually short or absent.
F
The length of time it takes a culture to double in cell number is called the ___.
Generation time
Direct cell counts of environmental samples generally result in ___ cell densities than methods that rely on culturing.
Higher
Microbes that grow best at temperatures between 85 and 113*C are called ___.
Hypothermophiles
Microbes that grow best as pH values near 7 are termed ___.
Neutrophiles
Microbes that CANNOT grow without oxygen are called ___.
Obligate aerobes
Measuring turbidity or total protein of a culture can be used to estimate cell mass and thereby estimate ___.
Population size
___ is a method for separating cells by mixing the cels within a liquid agar then dispersing the cells poured into a petri dish.
Pour plating
Microbes that grow best at temperatures of 15* are called ___.
Psychrophiles
The method for separating cells by dragging samples over different sectors of a plate using a microbial loop is called ___.
Streak plating
T/F Blood agar is both a differential and enriched medium.
T
T/F DNA of thermophiles is stabilized by binding of special nucleoid-associated proteins.
T
T/F Membranes of some thermophilic Archaea are stabilized by ether linked phospholipids.
T
T/F 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.
T
T/F 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.
T
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
B
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.
B
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.
B
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.
B
Media containing some ingredients of unknown chemical composition are called __________ media. A. undefined B. complex C. defined D. synthetic
B
Media in which all components and their concentration are known are called __________ media. A. transport B. defined C. selective D. enrichment
B
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
D
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
D
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.
D
When the number of cells in a culture is determined by microscopic observation, this is a type of ___ counting.
Direct counting
To increase the number of microbes with specific metabolic activities in a culture microbiologists use a technique known as ___.
Enrichment culture
Microorganisms that can grow under very harsh conditions are called ___.
Extremophiles
T/F A given medium can be either selective or differential but not both.
F
T/F A microbial environment containing high nutrient concentrations is called an oligotrophic environment.
F
T/F All bacterial and archaeal cells are diploid.
F
T/F During the lag phase of microbial growth, the cells are metabolically inactive.
F
T/F The purpose of the penicillin binding proteins is to link phospholipids together in the cellular membrane.
F
In a chemostat, the addition of nutrients provides energy for the microbes in culture. When nutrients are limiting, microbes first use the available energy for _____, then as nutrients increase they use the additional available energy for _____.
Maintenance; reproduction
An organisms optimal growth temperature is closest to its ___.
Maximal growth temperature
Microbes that grow best at 37*C are called ___.
Mesophiles
One would expect to find this protein involved in the elongation of Bacillus anthracis to form its typical shape. (QUIZ)
MreB
When a broth culture of Bacillus begins to run out of nutrients, the cells form _______.
endospores
Organisms that grow best at pH levels above 10 are called __________ __________.
extreme alkaliphiles
Growth media that will support the growth of many different types of microorganisms are called __________ __________ growth media, whereas those that are supplemented by blood or other rich nutrient sources in order to support the growth of fastidious organisms are called __________ media.
general purpose, enriched
The __________ __________ is the length of time it takes for a population of microorganisms to double in number.
generation time
Microbial __________ is an increase in cell constituents that may or may not be accompanied by an increase in cell number.
growth
Organisms that require high levels of sodium chloride in order to grow are called __________ organisms.
halophilic
Organisms that have their optimum growth pH between 5.5 and 8.0 are called __________.
neutrophiles
Quorum sensing in Gram-positive bacteria generally involves the use of ____________ as the external signaling molecules.
oligopeptides
The site at which replication of DNA starts in bacterial cells is known as the __________ of ___________.
origin, replication
Organisms that can grow in habitats with low water activity by maintaining a high internal salt concentration are called __________ organisms.
osmotolerant
A growth medium that favors the growth of some microorganisms but inhibits the growth of other microorganisms is a __________ medium.
A
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
A
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 these.
C
Microorganisms are most nearly uniform in terms of chemical and physiological properties during __________ phase. A. lag B. exponential C. stationary D. decline
B
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.
B
Organisms that grow well at 0C and have optimum growth temperatures of 15C or lower are called A. psychrotrophs. B. psychrophiles. C. frigiphiles. D. mesophiles.
B
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 these
B
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
B
The process of forming a cross wall between two daughter cells is known as A. replication B. septation C. sporulation D. mitosis
B
Agar is an excellent solidifying agent for microbiological media because A. it is not degraded by most microorganisms. B. solid agar remains solid until the temperature is raised to 90C, and liquid agar remains liquid if the temperature is lowered to 45C. C. it is not degraded by most microorganisms and solid agar remains solid until the temperature is raised to 90C, and liquid agar remains liquid if the temperature is lowered to 45C are correct. D. agar provides an excellent source of nutrition for a variety of different microorganisms.
C
During cytokinesis, a critical step in septation is the assembly of the A. replisome. B. spindle body. C. Z ring. D. cytoskeletal spiral.
C
For surface cultivation of microorganisms, a sulfated polymer called agar can be extracted from __________ and added to liquid media in order to cause it to solidify. A. bacteria B. animal fat C. algae D. fungi
C
Given a log phase bacterial culture with 1 x 10^6 cells per ml and a generation time of 30 minutes, how long does it take the culture to reach a density of 6.4 10^7 cells per ml? A. 1 hour B. 2 hours C. 3 hours D. 4 hours
C
Mannitol salt agar (MSA) only allows the growth of halophiles (salt-loving microbes). Among the halophiles, mannitol fermenters release acid that turns the pH indicator yellow; mannitol nonfermenters leave the medium red. Onto MSA you inoculate a halophilic mannitol fermenter, a nonhalophilic mannitol fermenter, and a halophilic mannitol nonfermenter. Thus, the medium is acting as a __________ medium. A. selective B. differential C. selective and differential D. neither selective nor differential
C
Most bacterial and archaeal cells divide by A. mitosis B. meiosis C. binary fission D. all of these
C
Organisms that ignore oxygen and grow equally well in its presence or absence are called A. facultative anaerobes. B. microaerophiles. C. aerotolerant. D. anoxygenic.
C
Organisms that ignore oxygen and grow equally well in its presence or absence are called A. facultative anaerobes. B. microaerophiles. C. aerotolerant. D. anoxygenic.
C
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
C
A macroscopically visible cluster of microorganisms on a solid growth medium is called a ___.
Colony
Mannitol salt agar (MSA) only allows the growth of halophiles (salt-loving microbes); nonhalophiles will not grow. Among the halophiles, mannitol fermenters will produce acid that turns the pH indicator yellow; mannitol nonfermenters leave the medium red. Onto MSA you inoculate a halophilic mannitol fermenter and a halophilic mannitol nonfermenter. In this case, the medium is acting as (a) __________ medium(s). A. selective B. differential C. selective and differential D. enrichment
D
Organisms that grow near deep-sea volcanic vents are likely to be A. psychrophilic. B. psychrotrophic. C. mesophilic. D. thermophilic.
D
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
D
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
D
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.
D
Which of the following can be used to isolate pure cultures of bacteria from mixtures? A. spread plates B. streak plates C. pour plates D. all of the choices
D
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.
D
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.
D
You would like to culture a bacterium that is growing in the lung of a human patient with pneumonia. Which media would be of most use in culturing this organism? A. Transport media. B. Mannitol salt agar. C. MacConkey's agar. D. Complex medium supplemented with whole blood. E. None of the choices.
D
T/F The size and shape of a colony is not useful for identification of a microorganism because most microorganisms produce colonies that are indistinguishable from one another.
F
In ___, a suspension of cells is distributed over the surface of a plate with a sterile bent rod.
Spread plating
Think about the properties of microbes growing in an oligotrophic environment. Cells in which of the stages of the typical bacterial growth curve most resemble cells growing in an oligotrophic environment?
Stationary phase
T/F 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.
T
T/F The growth rate of a given species of microorganism is dependent on the composition of the medium in which it is grown.
T
T/F: Numerous proteins found in biofilm are not observed when the same cells are planktonic.
T
The cell wall of bacteria constrains the ___________ _________ that results from the osmolarity of the cytoplasmic contents.
turgor pressure