Microbial Growth Practice Quiz Bank, Exam 2, Chapter 6

In Table 1, which medium (media) is (are) chemically defined? A) A B) B C) C D) A and B E) A and C

A) , Na2HPO4, KH2PO4, MgSO4, CaCl2, NaHCO3

Three cells with generation times of 30 minutes are inoculated into a culture medium. How many cells are there after 5 hours? A) 3072 B) 1024 C) 243 D) 48

A) =10 generations, 3-6-12-24-48-96-192-384-768-1536-3072 therefore answer is 3072

The addition of which of the following to a culture medium will neutralize acids? A) Buffers B) Sugars C) pH D) Carbon

A) Buffers!

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) Facultative anaerobes

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) Hypotonic

Which of the following pairs is mismatched? A) Psychrotroph - growth at 37°C B) Thermophile - growth at 60°C C) Mesophile - growth at 25°C D) Psychrophile - growth at 15°C

A) Psychrotroph - growth at 37 C

Differential media make it easier to distinguish colonies of different microbes A) True B) False

A) True

In Figure 2, which sections show a phase where the number of cells dying equals the number of new cells being produced? A) a and c B) b and d C) a and b D) c and d

A) a&c Lag and Stationary phase

In Figure 1, which line best illustrates the growth of a facultative anaerobe incubated aerobically?

A, ? FA makes ATP by aerobic respiration if O2 present

In Figure 1, which line best depicts a capnophile in the presence of high concentrations of CO2?

A, Capnophiles thrive in the presence of CO2

In Figure 1, which line best depicts the human pathogen Treponema Pallidum when allowed to grow inside the human body?

A, HUMAN pathogen, thus opt temp is at body temp.

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) Batch

Which of the following uses inorganic molecules such as H2S as an energy source? A) lithotrophs B) chemotrophs C) photoptrophs D) aerobes?

B) Chemotrophs

A culture medium consisting of agar, human blood, and beef heart is a A) Chemically defined medium. B) Complex medium. C) Selective defined medium. D) Differential defined medium.

B) Complex medium

Which of the following is an advantage of the standard plate count? A) Can readily count cells that form aggregates B) determines the number of viable cells C) can be performed on very dilute samples, such as lake water D) provides immediate results E) Can be used to count heat‐sensitive bacteria

B) Determines # of viable cells

Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt? A) Psychrophiles B) Facultative halophiles C) Anaerobes D) Thermophiles E) Hyperthermophiles

B) Facultative Halophiles -Have the ability to grow at high salt concentrations

Which of the following is an example of a metabolic activity that could be used to measure microbial growth? A) Standard plate count B) Glucose consumption C) Direct microscopic count D) MPN

B) Glucose consumption

During which growth phase will gram‐positive bacteria be most susceptible to penicillin? A) Lag phase B) Log phase C) Death phase D) Stationary phase E) The culture is equally susceptible during all phases.

B) Log phase

Some microbes can transform N2 into usable compounds; this is achieved by the process of A) Photosynthesis B) Nitrogen fixation C) Nitrogen reduction D) Anabolism E) Fermentation

B) Nitrogen fixation

Which of the following is the best definition of generation time? A) The length of time needed for lag phase B) The length of time needed for a cell to divide C) The minimum rate of doubling D) The duration of log phase E) The time needed for nuclear division

B) The length of time needed for a cell to divide

Which of the following is not generally true about biofilms? A) They may be considered microbial communities B) The organisms in them do not share nutrients C) They are much more resistant to drugs, in particular microbicides D) They usually begin when a free‐swimming bacterium attaches to a surface E) The CDC estimates that 70% of human bacterial infections involve biofilms

B) The organisms in them do not share nutrients

Which of the following is an organic growth factor? A) glucose B) vitamin B C) peptone D) Na2HPO4 E) H2O

B) Vitamin B

In Figure 2, which sections of the graph illustrate a logarithmic change in cell numbers? A) a and c B) b and d C) a and b D) c and d

B) b&d Lag and Death phase

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) microaerophiles

In Figure 1, which line best illustrates a mesophile at 5 C below its optimum temperature?

B, Mesophile optimum temperature is 20-45 C

A sample of milk is tested for its bacterial content in a plate count assay. A one-millileter sample of the milk is diluted in a 1:10 dilution series. One milliliter of the third dilution tube is plated in a pour plate. After incubation, the plate has 54 colonies, indicating that the original milk sample contained a. 540,000 cells. b. 540 cells. c. 54,000 cells. d. 54 cells. e. 5,400 cells. c. 54,000 cells.

C) , 3RD DILUTION PLATE, 10^-3, 54=54000

Most bacteria grow best at pH A) 1. B) 5. C) 7. D) 9.

C) 7, neutral

In Figure 3, in which tube is a strict capnophile growing? A) a B) b C) c D) d E) Cannot tell from data

C) ? growth only at the bottom, Strict capnophile opt with CO2

Most bacterial and archaeal cells divide by A) mitosis B) meiosis C) binary fission D) all of the above

C) Binary Fission

Microbes that require higher CO2 levels that are found in air are called A) facultative anaerobes B) microaerophiles C) capnophiles D) aerobes E) fastidious

C) Capnophiles

Organisms that must obtain their carbon in organic form are called A) parasites B) photosynthesizers C) heterotrophs D) autotrophs

C) Heterotrophs <-- cannot fix N2, need plants

Which of the following is an advantage of the direct microscopic count? A) Can readily count organisms that are motile B) Easily counts dead cells C) Requires no incubation time D) Requires a large number of cells

C) Requires no incubation time

The term facultative anaerobe refers to an organism that A) Doesn't use oxygen but tolerates it. B) Is killed by oxygen. C) Uses oxygen or grows without oxygen. D) Requires less oxygen than is present in air.

C) Uses oxygen or grows without oxygen

In Figure 1, which line shows the growth of an aerobe incubated anaerobically?

C, Duh

In Figure 1, which line best depicts a psychrophile incubated at room temperature?

C, psychrophiles growth best at < 10 C

The length of the bacterial 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) All of the choices ( condition of the microorganisms, the nature of the growth medium, temperature)

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) All of the choices ( direct counts of microbial cells, count of viable cells using colony growth procedures, measurements of microbial biomass)

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) All of the choices (min temp, max temp, opt temp)

Thirty‐six colonies grew in nutrient agar from 1.0 ml of undiluted sample in a standard plate count. How many cells were in the original sample? A) 4 B) 9 C) 18 D) 36

D) 36

An experiment began with 4 cells and ended with 128 cells. How many generations did the cells go through? A) 64 B) 32 C) 6 D) 5 E) 4

D) 4-8-16-32-64-128, each - equal 1 generation, therefore the answer is 5

Patients with indwelling catheters are susceptible to infections because A) Injected solutions are contaminated. B) Their immune systems are weakened. C) Infections can be transmitted from other people. D) Biofilms develop on catheters. E) Bacteria cause infections.

D) BIOFILMS! develop on catheters

An organic compound such as an amino acid or vitamin that cannot be synthesized by an organism and must be provided as a nutrient is called a A) key compound B) growth factor C) cofactor D) coenzyme E) complex nutrient

D) Coenzyme

Salts and sugars work to preserve foods by creating a A) Depletion of nutrients. B) Hypotonic environment. C) Lower osmotic pressure. D) Hypertonic environment.

D) HYPERtonic environment. Water moves out of the cell.

Which of the following is NOT a direct method to measure microbial growth? A) Direct microscopic count B) Standard plate count C) Filtration D) Metabolic activity

D) Metabolic activity

Organisms that grow near deep‐sea volcanic vents are likely to be A) psychrophilic. B) psychrotrophic. C) mesophilic. D) thermophilic.

D) thermophile

In Figure 3, in which is a microaerophile growing? A) a B) b C) c D) d E) e

E) , middle growth, microaerophiles need O2 but are poisoned by high concentrations