Exam 2 - Chapter 9 Book+HW/Quizzes Flashcards
Which of the following methods would be used to measure the concentration of bacterial contamination in processed peanut butter?
turbidity measurement
total plate count
dry weight measurement
direct counting of bacteria on a calibrated slide under the microscope
total plate count
In which phase would you expect to observe the most endospores in a Bacillus cell culture?
death phase
lag phase
log phase
log, lag, and death phases would all have roughly the same number of endospores.
death phase
During which phase would penicillin, an antibiotic that inhibits cell-wall synthesis, be most effective?
death phase
lag phase
log phase
stationary phase
log phase
Which of the following is the best definition of generation time in a bacterium?
the length of time it takes to reach the log phase
the length of time it takes for a population of cells to double
the time it takes to reach stationary phase
the length of time of the exponential phase
the length of time it takes for a population of cells to double
What is the function of the Z ring in binary fission?
It controls the replication of DNA.
It forms a contractile ring at the septum.
It separates the newly synthesized DNA molecules.
It mediates the addition of new peptidoglycan subunits.
It forms a contractile ring at the septum.
If a culture starts with 50 cells, how many cells will be present after five generations with no cell death?
200
400
1600
3200
1600
Filamentous cyanobacteria often divide by which of the following?
budding
mitosis
fragmentation
formation of endospores
fragmentation
. Which is a reason for antimicrobial resistance being higher in a biofilm than in free-floating bacterial cells?
The EPS allows faster diffusion of chemicals in the biofilm.
Cells are more metabolically active at the base of a biofilm.
Cells are metabolically inactive at the base of a biofilm.
The structure of a biofilm favors the survival of antibiotic resistant cells.
Cells are metabolically inactive at the base of a biofilm.
Quorum sensing is used by bacterial cells to determine which of the following?
the size of the population
the availability of nutrients
the speed of water flow
the density of the population
the density of the population
. Which of the following statements about autoinducers is incorrect?
They bind directly to DNA to activate transcription.
They can activate the cell that secreted them.
N-acylated homoserine lactones are autoinducers in gram-negative cells.
Autoinducers may stimulate the production of virulence factors.
They bind directly to DNA to activate transcription.
An inoculated thioglycolate medium culture tube shows dense growth at the surface and turbidity throughout the rest of the tube. What is your conclusion?
The organisms die in the presence of oxygen
The organisms are facultative anaerobes.
The organisms should be grown in an anaerobic chamber.
The organisms are obligate aerobes.
The organisms are facultative anaerobes.
An inoculated thioglycolate medium culture tube is clear throughout the tube except for dense growth at the bottom of the tube. What is your conclusion?
The organisms are obligate anaerobes.
The organisms are facultative anaerobes.
The organisms are aerotolerant.
The organisms are obligate aerobes.
The organisms are obligate anaerobes.
Pseudomonas aeruginosa is a common pathogen that infects the airways of patients with cystic fibrosis. It does not grow in the absence of oxygen. The bacterium is probably which of the following?
an aerotolerant anaerobe
an obligate aerobe
an obligate anaerobe
a facultative anaerobe
an obligate aerobe
Streptococcus mutans is a major cause of cavities. It resides in the gum pockets, does not have catalase activity, and can be grown outside of an anaerobic chamber. The bacterium is probably which of the following?
a facultative anaerobe
an obligate aerobe
an obligate anaerobe
an aerotolerant anaerobe
an aerotolerant anaerobe
Why do the instructions for the growth of Neisseria gonorrhoeae recommend a CO2-enriched atmosphere?
It uses CO2 as a final electron acceptor in respiration.
It is an obligate anaerobe.
It is a capnophile.
It fixes CO2 through photosynthesis.
It is a capnophile.
. Bacteria that grow in mine drainage at pH 1–2 are probably which of the following?
alkaliphiles
acidophiles
neutrophiles
obligate anaerobes
acidophiles
Bacteria isolated from Lake Natron, where the water pH is close to 10, are which of the following?
alkaliphiles
facultative anaerobes
neutrophiles
obligate anaerobes
alkaliphiles
. In which environment are you most likely to encounter an acidophile?
human blood at pH 7.2
a hot vent at pH 1.5
human intestine at pH 8.5
milk at pH 6.5
a hot vent at pH 1.5
A soup container was forgotten in the refrigerator and shows contamination. The contaminants are probably which of the following?
thermophiles
acidophiles
mesophiles
psychrotrophs
psychrotrophs
Bacteria isolated from a hot tub at 39 °C are probably which of the following?
thermophiles
psychrotrophs
mesophiles
hyperthermophiles
mesophiles
In which environment are you most likely to encounter a hyperthermophile?
hot tub
warm ocean water in Florida
hydrothermal vent at the bottom of the ocean
human body
hydrothermal vent at the bottom of the ocean
Which of the following environments would harbor psychrophiles?
mountain lake with a water temperature of 12 °C
contaminated plates left in a 35 °C incubator
yogurt cultured at room temperature
salt pond in the desert with a daytime temperature of 34 °C
mountain lake with a water temperature of 12 °C
Which of the following is the reason jams and dried meats often do not require refrigeration to prevent spoilage?
low pH
toxic alkaline chemicals
naturally occurring antibiotics
low water activity
low water activity
Bacteria living in salt marshes are most likely which of the following?
acidophiles
barophiles
halotolerant
thermophiles
halotolerant
EMB agar is a medium used in the identification and isolation of pathogenic bacteria. It contains digested meat proteins as a source of organic nutrients. Two indicator dyes, eosin and methylene blue, inhibit the growth of gram-positive bacteria and distinguish between lactose fermenting and nonlactose fermenting organisms. Lactose fermenters form metallic green or deep purple colonies, whereas the nonlactose fermenters form completely colorless colonies. EMB agar is an example of which of the following?
a selective medium only
a differential medium only
a selective medium and a chemically defined medium
a selective medium, a differential medium, and a complex medium
a selective medium, a differential medium, and a complex medium
Haemophilus influenzae must be grown on chocolate agar, which is blood agar treated with heat to release growth factors in the medium. H. influenzae is described as ________.
an acidophile
a thermophile
an obligate anaerobe
fastidious
fastidious
Capnophiles are bacteria that grow best under which of the following conditions?
relatively high CO2 and relatively low oxygen concentrations
relatively high oxygen and relatively low CO2 concentrations
relatively low CO2 and oxygen concentrations
relatively low oxygen and CO2 concentrations
relatively high CO2 and relatively low oxygen concentrations
Which of the following is the most common category of bacteria?
neutrophiles
acidophiles
alkaliphiles
extreme alkaliphiles
neutrophiles
Which type of microbes thrive in the Great Salt Lake?
extreme halophiles
barophilic
barotolerant
halotolerant
extreme halophiles
Halotolerant microbes cannot grow without high concentrations of salt.
True
False
False
Human pathogens are generally which type of microbe?
mesophiles
psychrophiles
psychrotrophs
thermophiles
mesophiles
Which best describes bacterial growth during the log phase of the growth curve?
exponential
linear
stationary
S-shaped
exponential
MacConkey agar can be used to select for the growth of gram-positive bacteria, making it especially useful to study Enterobacteriaceae.
True
False
False
Food spoilage is often caused by which type of microbe?
psychrotrophs
mesophiles
psychrophiles
thermophiles
psychrotrophs
Which of the following is the correct order of phases of growth in the growth curve of a batch culture?
lag phase, log phase, stationary phase, death/decline phase
death/decline phase, lag phase, log phase, stationary phase
log phase, lag phase, stationary phase, death/decline phase
statioary phase, log phase, lag phase, death/decline phase
lag phase, log phase, stationary phase, death/decline phase
A candle jar is often used to grow which type of bacteria?
capnophiles
microaerophiles
obligate aerobes
obligate anaerobes
capnophiles
