Microbiology Chapter 4: Dynamics of Prokaryotic Growth

Some species of microorganisms can be found in environments where no unprotected human could survive.

True or False

True

This figure shows a bacterium dividing. The mechanism is called
__________________.

Binary fission

Which environment is more dynamic and complex?

1. A laboratory environment

2. Soil and its surroundings

Soil and its surroundings

What term is used to describe a group of microbes co-existing in polymer-encased communities?

1. Slime film

2. Biofilm

3. Biolayer

4. Slime layer

Biofilm

Consider interactions of mixed microbial communities. Match the descriptions in the left column with those that best correlate with them in the right column.

Difficult to reproduce in the laboratory →

Simpler to reproduce in the laboratory →

Inhibit competitors →

Nutrients for another microbe →

Creation of low O₂ microenvironment →

1. Pure cultures

2. Synthesis of toxic compounds

3. Consumption of O₂ by aerobic growth

4. Production of metabolic wastes by one microbe

5. Conditions in close microbial associations

1. Difficult to reproduce in the laboratory → Conditions in close microbial associations

2. Simpler to reproduce in the laboratory → Pure cultures

3. Inhibit competitors → Synthesis of toxic compounds

4. Nutrients for another microbe → Production of metabolic wastes by one microbe

5. Creation of low O₂ microenvironment → Consumption of O₂ by aerobic growth

Imagine you are a microbiologist trying to isolate new species of prokaryotes. You collect numerous samples and return to your lab, where you proceed to encourage any prokaryotes present to grow. Disappointingly, you are not successful. Which is the LEAST likely explanation for this outcome?

1. You did not manage to provide them with all the major elements, trace elements, and growth factors necessary to support their growth.

2. There were no prokaryotes present where you sampled.

3. Your atmospheric conditions did not sufficiently match those found in their environment.

4. Compounds or conditions that you provided inhibited their growth.

5. The prokaryotes depended on a close association with others in order to grow.

There were no prokaryotes present where you sampled.

A(n) ________ culture contains only ONE species of microorganisms descended from a single cell.

pure

Bacteria and archaea typically divide by a process known as
________________.

binary fission

A colony is a distinct mass of microorganisms which develop from a single cell growing on a solid medium.

True or False

True

Bacteria growing in a natural environment experience ______.

1. dynamic and complex conditions

2. conditions similar to that of the laboratory

dynamic and complex conditions

The polysaccharide found in marine algae that is commonly used to solidify culture media is called ______.

1. agar

2. peptone

3. starch

4. gelatin

agar

Many bacterial communities secrete polysaccharides and other hydrophilic polymers. This mesh-like accumulation can help protect the bacteria growing within from antibiotics or disinfectants.

These communities are called ___________.

biofilms

Select all that apply.

A batch culture has which of the following characteristics?

1. It is an open system.

2. It is a closed system.

3. Nutrients are not renewed.

4. Cells are maintained in a state of continuous growth.

5. It typically involves growth of bacteria or archaea either on agar plates or in tubes or flasks of broths.

6. Wastes are not removed.

1. It is a closed system.

2. Nutrients are not renewed.

3. It typically involves growth of bacteria or archaea either on agar plates or in tubes or flasks of broths.

4. Wastes are not removed.

Which of the following does not describe interactions of mixed microbial communities?

1. Microbial cells can consume O₂, creating microenvironments in which anaerobes can thrive.

2. Conditions in mixed microbial associations are readily reproduced in the laboratory.

3. Some microbes can synthesize toxic compounds to inhibit competitors.

4. Microbes can interact cooperatively and even foster the growth of species that otherwise could not survive.

5. Microbes can compete for nutrients.

Conditions in mixed microbial associations are readily reproduced in the laboratory.

A graphical representation of a changing population size over time is called which of the following?

1. histogram

2. growth curve

3. generation time

growth curve

Which of the following is most likely to be a pure culture?

1. A single colony growing on a streak plate.

2. A bacterial lawn of growth covering an agar plate.

3. A Petri dish covered with bacteria following inoculation from a single patient.

4. A broth culture growing in a flask.

A single colony growing on a streak plate.

___________ phase describes the initial phase after bacterial cells are placed into a new environment and are gearing up for cell division, but their numbers have not yet increased.

Lag

An isolated ___________ is a distinct mass of microorganisms appearing on a solid medium, arising from the multiplication of a single cell.

colony

The log (logarithmic) phase of a normal growth curve is also referred to as the ___________ phase.

exponential or exponential growth

Culture media are usually solidified by the addition of a polysaccharide extracted from seaweed. This polysaccharide is known as ______________.

agar

The ____________ phase of the bacterial growth curve is when there are an equal number of cells dividing as there are dying.

stationary

When bacteria or archaea are grown on agar plates or in tubes or flasks of broth, these closed systems are a ___________ culture. By contrast, cells can also be grown in an open system, or a continuous culture.

batch

In a growth curve, cell numbers increase exponentially during the log phase and decrease exponentially during the death phase.

True or False

True

The characteristic pattern that shows the changes in size of a bacterial population over time in a broth culture is called a bacterial
____________________.

growth curve

Select all that apply.

In what ways is microbial growth in a colony the same as growth in a liquid?

1. Cells in both situations experience the same levels of nutrients.

2. Cells in either situation are all in the same phase of growth at the same time.

3. Both involve a lag phase followed by exponential growth.

4. In both cases, cells compete with one another for available nutrients.

1. Both involve a lag phase followed by exponential growth.

2. In both cases, cells compete with one another for available nutrients.

Which of the following characterizes the lag phase of a normal bacterial growth curve?

1. Cells are synthesizing enzymes needed for growth but not increasing in number.

2. Cells are undergoing logarithmic cell division.

3. Depletion of nutrients and buildup of waste. While some cells multiply, others die, and the overall population remains relatively constant.

4. Cells are declining exponentially.

Cells are synthesizing enzymes needed for growth but not increasing in number.

Which device is used to keep cells in a state of constant growth?

1. NMR

2. Spectrophotometer

3. Chemostat

4. Thermocycler

5. Flow cytometer

Chemostat

In which phase of the growth curve is the generation time measured?

1. Lag

2. Death

3. Stationary

4. Log

Log

Some microorganisms live in harsh environments that kill most other organisms. The term used to describe an organism with this characteristic is _______________.

extremophiles

During which phase of growth does the number of new cells balance the number of declining cells?

1. Lag phase

2. Log phase

3. Death phase

4. Stationary phase

Stationary phase

Which of the following describes the optimum temperature of a psychrophile relative to a thermophile?

1. It is higher than a thermophile.

2. It is lower than a thermophile.

3. It is the same as a thermophile.

It is lower than a thermophile.

In which phase of the growth curve is the number of viable cells decreasing?

1. log

2. death

3. stationary

4. lag

death

Match the term on the left with the description of the optimum temperature environment.

psychrophile →

psychrotroph →

mesophile →

thermophile →

1. human body

2. refrigeration

3. compost heap

4. cold Arctic regions

1. psychrophile → cold Arctic regions

2. psychrotroph → refrigeration

3. mesophile → human body

4. thermophile → compost heap

Select all that apply.

Why are cells growing in a colony on solid media likely to be in many more different phases of growth than cells growing in liquid culture?

1. Growth on solid media provides a greater abundance of nutrients, so cells are able to rapidly separate out into different phases of growth.

2. Unlike cells on the edge of a colony, those in the center of a colony face depleted levels of nutrients and O₂, yielding different phases of growth.

3. Cells grow much more quickly in liquid culture, so they are more likely to stay in the same phase.

4. Cells in liquid culture experience a relatively uniform environment, so they are much more likely to be in the same phase of growth.

1. Unlike cells on the edge of a colony, those in the center of a colony face depleted levels of nutrients and O₂, yielding different phases of growth.

2. Cells in liquid culture experience a relatively uniform environment, so they are much more likely to be in the same phase of growth.

Which term describes a microorganism that has an optimum temperature between -5⁰C and 15⁰C?

1. Thermophile

2. Psychrophile

3. Mesophile

4. Psychrotroph

Psychrophile

A continuous culture system that adds nutrients and removes waste in order to maintain a constant growth rate and cell density is called a ______________.

chemostat or bioreactor

Which term describes a microorganism that has an optimal temperature between 15^∘C and 30^∘C, but grows well on refrigerated foods?

1. Psychrotroph

2. Mesophile

3. Thermophile

Psychrotroph

Select all that apply.

Consider the following environmental factors. Which have the most impact on microbial growth?

1. odor

2. wind speed

3. pH

4. atmosphere

5. water availability

6. temperature

1. pH

2. atmosphere

3. water availability

4. temperature

A species grows most rapidly at its ___________ growth temperature.

optimum, optimal, or ideal

E. coli and most other common bacteria are ______.

1. thermophiles

2. psychrophiles

3. mesophiles

4. psychrotrophs

5. hyperthermophiles

mesophiles

The five groups used to categorize microorganisms with respect to growth temperature (psychrophile, psychrotroph, mesophile, thermophile, and hyperthermophile) ______.

1. are based on optimum growth temperatures.

2. are precise with respect to the dividing lines between each group.

3. represent the entire range at which the organisms in the groups can grow.

are based on optimum growth temperatures.

An environment with little or no O₂ present is called a(n) ______________ environment.

anaerobic

If you wanted to study psychrophilic microorganisms, you would most likely find them ______.

1. in water from a hot tub

2. in lakes fed by glaciers

3. growing on your skin

in lakes fed by glaciers

A ______ is most likely to be implicated in spoilage of refrigerated foods.

1. mesophile

2. hyperthermophile

3. psychrotroph

4. thermophile

psychrotroph

Some microorganisms live in harsh environments that kill most other organisms. The term used to describe an organism with this characteristic is _____________.

extremophiles

A(n) ___________ aerobe, or strictly aerobic organism, requires O₂ for survival.

obligate

Human pathogens, adapted to growth in the human body, are ______.

1. psychrophiles

2. mesophiles

3. psychrotrophs

4. hyperthermophiles

5. thermophiles

mesophiles

If O₂ is present in an environment, it is said to be _______.

1. aerobic

2. aerophilic

3. aerotactic

aerobic

Select all that apply

Which of the following correctly describe facultative anaerobes?

1. They can grow without O₂.

2. Their growth is faster when O₂ is available.

3. They can only grow in the absence of O₂.

4. They can grow in the presence of O₂ but do not use it to harvest energy.

1. They can grow without O₂.

2. Their growth is faster when O₂ is available.

Which term describes a microorganism that has an optimum temperature between -5⁰C and 15⁰C?

1. Psychrotroph

2. Psychrophile

3. Mesophile

4. Thermophile

Psychrophile

Bacteria that cannot multiply if O₂ is present, and are often killed by even brief exposure to air, are termed ______________.

obligate anaerobes

A(n) ___________ is an aerobe that requires O₂ at a concentration less than that in the atmosphere.

microaerophile

Which of the following describes a microbe that must have O₂ to survive?

1. Obligate aerobe

2. Passive aerobe

3. Semi aerobe

4. Facultative aerobe

Obligate aerobe

Which of the following organisms does not use O₂ at all for growth?

1. Facultative anaerobe

2. Aerotolerant anaerobe

3. Microaerophile

Aerotolerant anaerobe

Regardless of the pH of the external environment, microbial cells maintain a constant internal pH, typically near neutral. For example, prokaryotes that grow in alkaline conditions bring ____________ into the cell.

protons, H+, hydrogen, or hydrogen ions

From which body site could a facultative anaerobe be isolated?

1. Deep wound

2. Intestine

3. Surface of skin

4. Any of these locations

Any of these locations

If you inoculated a test tube of cooled liquid agar with an obligate anaerobe and incubated it, where would you expect to find growth?

1. Only at the top of the tube.

2. Only at the bottom of the tube.

3. Throughout the tube.

Only at the bottom of the tube.

If the solute concentration is higher outside the cell than inside the cell, water will diffuse out due to osmosis. This will result in _________________.

plasmolysis

A microbe that requires small amounts of O₂ (2-10%) for aerobic respiration but is inhibited by higher concentrations is called a(n) ______.

1. microaerophile

2. obligate aerobe

3. aerotolerant anaerobe

4. facultative anaerobe

microaerophile

A microbe that doesn't use O₂ but can grow in environments containing O₂ is described as a(n) ____________ anaerobe.

aerotolerant

Microbial cells must maintain a near-neutral internal pH. Because of this, bacteria that grow in acidic environments have mechanisms to ______.

1. bring H⁺ into the cell

2. pump out H⁺ that enter the cell

3. pump out OH^- that enter the cell

4. bring OH^- into the cell

pump out H⁺ that enter the cell

What term is used to describe chemical substances such as carbon or phosphorous, which are found in large quantities in cells?

1. Macromolecule

2. Macrocompound

3. Megamolecule

4. Macroelement

5. Major element

Major element

An organism that must consume organic matter is called a(n) ______________.

heterotroph

Which answer best explains the events in the figure leading to plasmolysis?

1. The solute concentration inside the cell is greater than outside the cell, causing water to diffuse out of the cell via osmosis.

2. There is a greater concentration of water outside the cell, so water flows from inside to outside the cell.

3. The solute concentration of the medium is greater than that in the cell, causing water to diffuse out of the cell due to osmosis.

4. There is more solvent outside the cell than inside, so water exits the cell.

The solute concentration of the medium is greater than that in the cell, causing water to diffuse out of the cell due to osmosis.

A(n) ___________ is an aerobe that requires O₂ at a concentration less than that in the atmosphere.

microaerophile

What term is used to describe organisms that use CO₂ as a carbon source?

1. Heterotrophs

2. Saprotrophs

3. Autotrophs

Autotrophs

Which of the following organisms does not use O₂ at all for growth?

1. Microaerophile

2. Facultative anaerobe

3. Aerotolerant anaerobe

Aerotolerant anaerobe

Carbon, oxygen, hydrogen, nitrogen, sulfur, and phosphorus, are examples of chemical substances called _____________, which are essential components of cell’s macromolecules.

major elements

Autotrophs play a crucial role in the cycling of carbon in the environment by converting inorganic carbon to an organic form. This process is called carbon ______________.

fixation

Which type of organism requires organic compounds for its carbon and energy needs?

1. Heterotroph

2. Autotroph

3. Phototroph

Heterotroph

Select all that apply.

Which of the following contain nitrogen?

1. DNA

2. Fats

3. Proteins

4. RNA

5. Carbohydrates

1. DNA

2. Proteins

3. RNA

A(n) __________ requires only carbon dioxide as a sole carbon source.

autotroph

Nitrogen fixation is the process by which some prokaryotes convert atmospheric nitrogen into ____________ and then incorporating that into cellular material.

ammonia or NH3

A microbe that doesn't use O₂ but can grow in environments containing O₂ is described as a(n) __________ anaerobe.

aerotolerant

A ______________ factor is an organic compound, such as a vitamin or an amino acid, that a given microorganism cannot synthesize and therefore must be provided in the growth medium.

growth

Animals could not survive without autotrophs because without them the world would run out of ______.

1. inorganic nitrogen

2. inorganic carbon

3. organic carbon

4. organic nitrogen

organic carbon

An organism that gets its energy directly from sunlight is called a(n)
______________.

phototroph

Unlike sugar, proteins provide which of the following elements?

1. Oxygen

2. Carbon

3. Nitrogen

4. Hydrogen

Nitrogen

A photoautotroph obtains energy from ______ and carbon from ______ in order to make organic compounds.

1. inorganic chemicals; CO₂

2. sunlight; organic compounds

3. sunlight; CO₂

4. organic compounds; organic compounds

sunlight; CO₂

Which describes the various laboratory media used to cultivate bacteria?

1. There are few different types.

2. They are all similar with respect to their nutrient content.

3. They are diverse in nutrient content and consistency.

They are diverse in nutrient content and consistency.

Some microorganisms can convert nitrogen gas (N₂) to ammonia in a process called _______.

1. nitrogen assimilation

2. nitrogen fixation

3. denitrification

4. nitrification

nitrogen fixation

Select all that apply.

Which of the following describe selective media?

1. Inhibit the growth of certain species

2. Allow the growth of desired organisms

3. Display visible differences among microorganisms

4. Select for growth of a broad spectrum of organisms

1. Inhibit the growth of certain species

2. Allow the growth of desired organisms

What term is used to describe essential organic compounds, such as a vitamin or amino acid, that must be provided in the diet?

1. Growth factors

2. Trace element

3. Virulence factors

4. Inhibitory regulators

Growth factors

Selective media are used for which of the following?

1. Growing a broad spectrum of microbes

2. Isolating a specific microbe from a mixed population

3. Growing fastidious microbes only

4. Differentiating a specific microbe from a mixed population

Isolating a specific microbe from a mixed population

Which term is used to describe organisms that can obtain energy directly from sunlight?

1. Saprotrophs

2. Phototrophs

3. Chemotrophs

Phototrophs

Which of the following best describes how the atmospheric needs of aerobic microbes can be met?

1. In a sealed container flushed with a gas like CO₂ to remove all the O₂.

2. In a special aerobic chamber.

3. By growing them in the air.

By growing them in the air.

An autotrophic organism that uses light for energy and carbon dioxide as a carbon source is termed a _________.

photoautotroph

Which is the best general description of a medium used to support bacterial growth in a Petri dish?

1. It contains only agar, which serves as a rich source of nutrients to support a diversity of microbial growth.

2. It must contain all possible nutrients, so that all microbes can grow.

3. It must have minimal nutrient content, so that microbes are forced to manufacture their required nutrients.

4. It contains only agar because contact with the air will provide the rest of the nutrients.

5. It may have very few nutrients, or it may have many different nutrients to support widely varying growth requirements.

It may have very few nutrients, or it may have many different nutrients to support widely varying growth requirements.

How might an enrichment culture be used to isolate organisms capable of nitrogen fixation?

1. Provide media that are rich in nitrogen in an inorganic form

2. Exposing the culture to sunlight to encourage photosynthetic growth

3. Using a media that does not contain any form of nitrogen, and exposing it to the atmosphere

4. Exposing the culture to atmospheric nitrogen gas

Using a media that does not contain any form of nitrogen, and exposing it to the atmosphere

A medium that contains an ingredient that inhibits the growth of some bacteria, while allowing others to grow, is called a(n) ____________ medium.

selective

A direct cell count determines the number of ______ in a sample

1. dead cells only

2. live cells only

3. total cells

total cells

Media used to isolate specific types of microorganisms from saliva, feces, or any other sample that contains many microbial species are called ______________.

selective

How are liquid batch cultures most often aerated to support the growth of aerobic microbes?

1. Pure O₂ flows under pressure from a gas cylinder into the tubes or flasks to supply maximum O₂.

2. Air is pumped into the tubes or flasks to supply sufficient O₂.

3. They are grown in tubes or flasks that are shaken continuously.

They are grown in tubes or flasks that are shaken continuously.

Viable cell counts determine the number of ______.

1. live cells

2. total cells (live and dead)

3. cells capable of multiplying

cells capable of multiplying

The viable plate method is based on the principle that each colony represents ___________ cell or colony-forming unit.

one

You are setting up an enrichment culture to look for bacteria that can use phenol as a carbon source. In your medium, you provide a variety of major elements and trace elements, plus phenol. Other than that contained in the phenol, what must you avoid adding if you hope to enrich for phenol-degraders?

1. Carbon

2. Iron

3. Phosphorus

4. Potassium

5. Nitrogen

Carbon

The steps shown in this figure are part of a technique called
____________.

serial dilution

A direct cell count typically determines only the number of live cells in a sample.

True or False

False

The term that describes the appearance of a cloudy broth culture is
_____________.

turbidity

Some microorganisms produce acids during metabolism. Which of the following would be a strong indication of this activity?

1. pH of the culture medium would remain unchanged after growth

2. pH of the culture medium would be higher after growth

3. pH of the culture medium should be lower after growth

pH of the culture medium should be lower after growth