Micro Ch6 Microbial nutrition and Growth

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Oriorden Spring 2013

Which of the following contributes to osmotic pressure in a cell?

water

Organisms that use light as their energy source and carbon dioxide as their carbon source are considered __________.

photoautotrophs

An aerotolerant anaerobe is a bacterium that ...............

is able to detoxify oxygen, but does not use it for its metabolism

Which of these would NOT be considered a growth factor for bacteria?

phosphorus
amino acids
purines and pyrimidines
vitamins

phosphorus

Why is NADH an important growth factor for microorganisms?

It serves as an electron carrier in energy-producing pathways.

All of the following can possibly denature proteins EXCEPT __________.

-alkaline pH
-temperatures exceeding the maximum growth temperature
-temperatures below the minimum growth temperature
-acid pH

temperatures below the minimum growth temperature. (Organisms may survive below this temperature and proteins are not denatured; they simply won't reproduce)

Organized collections of bacteria that attach to surfaces and are associated with many disease processes are called __________.

biofilms

Which of the following is NOT a method for isolating bacteria in a pure culture?
-streak-plate method
-serial dilutions of broth media
-lyophilization
-pour-plate technique

lyophilization

A pure culture of bacteria is typically derived from __________.
-a single cell
-a colony-forming unit
-at least two cells
-a group of cells

a colony-forming unit (It is possible for a colony to arise from a single cell.)

Which of the following is an inorganic carbon source?

-glucose
-triglycerides
-carbon dioxide
-amylose

carbon dioxide

Which of the following is NOT a characteristic of a complex medium?

-Complex media are especially helpful in growing organisms whose exact nutritional requirements are unknown.
-Complex media are used for routine growth of many different species of bacteria.
-The exact chemical composition is known.
-Nutrient broth and trypticase soy agar are examples of complex media.

The exact chemical composition is known.

In which of the following solutions would a cell become crenated?


-hypertonic solutions

-hypotonic solutions

-acidic solutions

-isotonic solutions

hypertonic solutions (ph alone does not affect osmosis)

Which of these statements does NOT describe differential media?


-Blood agar is considered a differential medium.
-Differential media favor the growth of some organisms while inhibiting the growth of others.
-It is possible for some differential media to also be selective.
-Carbohydrate fermentation tubes can be considered differential media.

Differential media favor the growth of some organisms while inhibiting the growth of others.

The majority of bacteria reproduce using __________.

-spontaneous generation
-mitosis
-binary fission
-meiosis

binary fission

Which happens first in bacterial cell division?
-The DNA is replicated.
-Chromosomes move into two separate regions of the cell.
-The cell elongates.
-The mitotic spindle forms

The DNA is replicated.

Which growth phase occurs first, after placing an inoculum into a nutrient broth?
-death phase
-stationary phase
-lag phase
-log phase

lag phase

Which of these is NOT a direct method of measuring microbial reproduction?
-serial dilution and viable plate counts
-microscopic counts
-turbidity
-Coulter counter

turbidity

An obligate anaerobe __________.
-can be cultured in a GasPak
-grow throughout thioglycollate broth
-possess catalase and peroxidase
-can survive in the presence of superoxide radicals, but not free oxygen

can be cultured in a GasPak

Bacteria that grow in high salt concentrations are termed __________.
-mesophiles
-psychrophiles
-halophiles
-barophiles

halophiles

A chemostat __________.

-is used to count bacteria
-is a device used to culture obligate anaerobes
-is a device that maintains a bacterial culture in a particular phase of growth
-is a method used to isolate bacteria into pure culture

is a device that maintains a bacterial culture in a particular phase of growth

_________ _________ is created as cells rapidly lose or gain water when they are in hypertonic or hypotonic solutions.

Osmotic pressure

-uses oxygen when present, but can also grow in the absence of oxygen

facultative anaerobe

Vitamins are considered a growth factor for _________.

bacteria.

_________ is a generic term meaning "a discrete mass of one type of bacterial cell";

Colony

The pour-plate technique is a method used to isolate__________.

bacteria.

- lipids which are a major organic source of carbon for cells.

triglycerides

__________ ________ _______can be used to distinguish those bacteria that can ferment the carbohydrate from those that cannot.

Carbohydrate fermentation tubes

_________ __________ are killed by the toxic forms of oxygen, including superoxide radical.

Obligate anaerobes

When organisms cannot use oxygen as an electron acceptor in cellular respiration, they often use ________or________ instead.

nitrates or sulfates

__________ prefer growth temperatures in the range of 20°C to 40°C.

Mesophiles

While pure cultures of bacteria may be grown in a chemostat, it is not used for _________ of bacteria.

isolation

Most bacteria divide by which method?

Binary fission

If you begin with three cells, how many cells would you have after three rounds of division?

24

Which of the following is NOT a step in bacterial cell division?

-splitting apart of two new daughter cells -disappearance of nuclear envelope -replication of the genetic material cell elongation

Disappearance of nuclear envelope

Which of the following represent a true statement about the resulting new daughter cells?

They are unable to divide. They are genetically identical to the parent. Four new daughter cells result from one parental cell. They share characteristics of both parental cells.

They are genetically identical to the parent

Which of the following characteristics is a hallmark of bacterial growth?

After several rounds of division, the genetic diversity of the bacterial population will be very diverse. Since the number of bacterial cells double after each round of replication, the number of cells rapidly increases. All daughter cells produced will be smaller than the parent.

Bacterial growth is fast because all bacterial cells undergo mitosis.

Since the number of bacterial cells double after ach round of replication,the number of cells rapidly increases.

Which of the following bacterial cell structures increases in size during binary fission?

cell wall bacterial chromosome cell membrane cytoplasm. both the cell wall and cell membrane all of the above

All of the above

Why is binary fission more quick and efficient when compared to eukaryotic cell division?

Bacteria do not need to form a mitotic spindle nor dissolve a nuclear membrane.

Put the following steps of bacterial replication in order, starting from a parent cell. Cell elongation Septum formation Chromosome replication Separation of daughter cells

3, 1, 2, 4

Which of the following statements is true for binary fission?

Binary fission results in the production of two genetically identical daughter cells. Binary fission results in the production of one genetically identical daughter cell.

Binary fission occurs as quickly as eukaryotic mitosis.

Replicated chromosomes are separated by attaching to a mitotic spindle.

Daughter cells must mature before they are able to perform binary fission.

Binary fission results in the production of two genetically identical daughter cells.

Starting with a single parent cell, how many cells would there be after four rounds of binary fission?

4
8
12
16
32

16

Why is it useful to plot bacterial growth on a logarithmic graph?

Because the number of cells increases rapidly, a logarithmic graph allows you to visualize the complete growth curve.

During which phase of bacterial growth will the number of dying cells exceed the number of new cells being made?

Death phase

Why do cells that are placed in fresh media not immediately enter logarithmic phase of growth?

The cells need to switch their metabolic state from a dormant one to an actively growing one.

During which phase of bacterial growth would you see cell dividing most rapidly?

Log phase

During which phase of growth would you find the highest number of total cells, both living and dead?

Stationary phase

Which of the following could be an optimal pH for the growth of an acidophile?

pH 11.0
pH 3.0
pH 7.0
pH 8.5

pH 3.0

A cell that uses an organic carbon source and obtains energy from light would be called a __________.

photoheterotroph

Which of the following is NOT a toxic form of oxygen?

peroxide anions
hydroxide ion
superoxide radicals
singlet oxygen

hydroxide ion

Which of the following groups of microbes does not undergo aerobic metabolism, but can detoxify oxygen enough to live in its presence?

microaerophiles
obligate anaerobes aerotolerant anaerobes facultative anaerobes

aerotolerant anaerobes

Which of the following statements concerning nitrogen is FALSE?

-Nitrogen is rarely a growth-limiting nutrient.
-All cells can recycle nitrogen from their nitrogen-containing molecules.
-Only a few types of bacteria can engage in nitrogen fixation.
-Nitrogen is essential for the production of amino acids and nucleotide bases

Nitrogen is rarely a growth-limiting nutrient

Organic molecules that prokaryotic organisms need, but cannot synthesize by themselves, are called __________.

growth factors

A microbe isolated from deep in the ocean could best be characterized as a __________.

barophile and psychrophile

All of the following are true statements regarding clinical specimens EXCEPT __________.

Clinical specimens must be properly labeled.

-clinical specimens include saliva, feces, and blood

-universal precautions are observed in order to protect specimens from contamination
-clinical specimens are often transported in special media to help preserve them

universal precautions are observed in order to protect specimens from contamination

All of the following are associated with the streak plate method of isolation EXCEPT __________.

-colonies will be found growing at and below the surface of the medium
-a sterile inoculating loop or needle is used
-the purpose is to isolate colony-forming units (CFUs) from one another
-a solid medium in a Petri dish is used in this technique

colonies will be found growing at and below the surface of the medium

Which of the following is NOT an advantage conferred on microbial cells by a biofilm?

-protection from environmental stresses --formation of microenvironments
-ability to stick to a substrate
-extension of the microbial growth phase

extension of the microbial growth phase

Why is agar a useful substance in the microbiology lab?

Agar does not solidify until it cools to about 40°C.

Which of the following is both a selective and a differential medium?

-nutrient broth
-blood agar
-MacConkey agar -Sabouraud dextrose agar

MacConkey agar

A psychrophile might grow best in which of the following environments?

a thermal pool
a refrigerator
the human body
a candle jar

a refrigerator

A candle jar would be most useful in isolating which of the following?
-fastidious microbes
-capnophiles
- psychrophiles
-biofilms

capnophiles

A bacterial species has been determined to have a generation time of 30 minutes. If a microbiologist starts with an inoculum of 1000 cells/ml, and wants to grow it to a culture of 1,000,000 cells/ml, approximately how long should the culture be incubated?

5 hours

Bacterial cultures go through lag phase because .....................

they are synthesizing new enzymes in order to use nutrients in their medium

All of the following statements concerning the bacterial growth curve are true EXCEPT __________.

-when death phase is reached, all cells in the culture have died

-during stationary phase, the number of dying cells equals the number of cells being produced
- under certain conditions, the log phase can be maintained indefinitely

-cells divide at a maximal rate during the log phase

when death phase is reached, all cells in the culture have died

All of the following are direct methods of measuring microbial growth EXCEPT __________.

-a Coulter counter
-viable plate counts -turbidity
- membrane filtration

turbidity

If a cell counter slide is determined to have a mean number of 20 bacterial cells per square, the total number of bacteria per ml of culture would be __________.

25,000,000

All of the following are drawbacks to the use of spectrophotometry in estimating microbial growth EXCEPT __________.

-it cannot distinguish between live and dead cells

-it kills the organisms as they are being counted

-it cannot be used if there are less than one million cells per milliliter

-it will underestimate the true number of cells if they are not uniformly in suspension

it kills the organisms as they are being counted

The MPN (most probable number) method of measuring microbial growth is one of the easiest and quickest methods.
-true
-false

false

Flow cytometry involves the counting of cells that have fluorescent dyes associated with them.
True
False

true

Direct methods of measuring microbial growth are more accurate than indirect methods.

True
False

false

Bacterial growth curves are plotted on graphs that have a logarithmic scale on both the x- and y-axes.
True
False

false

The quantity n2 represents the number of cells that arise from a cell that reproduces by binary fission.
True
False

false

Cells that divide by binary fission in different planes produce a chain formation of cells.

True
False

false

Blood agar is an example of a complex medium.

True
False

true

Facultative halophiles do not require the presence of high salt concentrations in order to grow.
True
False

true

Bacteria that are pathogenic for humans are usually classified as mesophiles.
True
False

true

When organisms are exposed to temperatures higher than their maximum growth temperature, their proteins are permanently denatured.

True
False

true

Most bacterial cells divide using a process called binary fusion.

True
False

false
(Fusion means to join together. Bacterial cells divide using binary fission, not fusion.)

Refrigeration kills all bacterial cells except psychrophiles.

True
False

false

Nitrogen fixation __________.

involves reduction of nitrogen gas to ammonia

-is the oxidation of nitrogen gas to from amino acids

-is the process that incorporates nitrogen into nucleotides

-is carried out by all bacteria

involves reduction of nitrogen gas to ammonia

The majority of bacteria and archaea have not or cannot be grown in the laboratory.
True
False

true

The term lithotroph is used to describe organisms that __________.

-require only small amounts of oxygen to survive
-live in extremely cold climates
-require high concentrations of CO2 for their growth

-obtain their electrons or hydrogen ions from an inorganic source

obtain their electrons or hydrogen ions from an inorganic source

A reducing medium is most often used for growing fastidious bacteria that have very specific nutritional requirements.
True
False

false

Quorum sensing is __________.
-a process used by bacteria to detect population density and activate genes for new characteristics
-an indirect method for microbiologists to measure the growth of bacterial populations
-a mechanism used by bacteria to inactivate toxic forms of oxygen
-a process used by bacteria to detect the osmotic pressure in their environment

a process used by bacteria to detect population density and activate genes for new characteristics

Which of these media is NOT an example of a differential medium?
-trypticase soy agar
-carbohydrate utilization broth
-blood agar
-MacConkey agar

trypticase soy agar

When performing serial dilutions and viable plate counts, the concentration of microorganisms is usually expressed as number of bacteria per milliliter.

True
False

false

(*The concentration is expressed in colony-forming units, or CFU, per milliliter.)

Most pathogenic bacteria would be classified as __________.

-photoautotrophs
-chemoautotrophs
-photoheterotrophs
-chemoheterotrophs

chemoheterotrophs

A chemostat could be used to keep a bacterial culture in the log phase indefinitely.

True
False

true

-These organisms use chemical forms of energy and they obtain their carbon from inorganic sources.

chemoautotrophs

-This is a toxic form of oxygen.

superoxide radicals

-These are aerobes that require an environment with 2-10% oxygen.

microaerophiles

Once solidified, agar will not melt at temperatures below ________.

100°C.

Since psychrophiles grow best at temperatures below______, a refrigerator would be the best environment for their growth.

15°C

Because the number of dying cells is roughly equal to the number of cells still dividing, the graph appears as a flat line during ____________phase

stationary

The MPN method involves 15 tubes at different growth dilutions and it requires a____-hour incubation period.

48

Since it contains actual blood, blood agar supplies a variety of growth factors, making it a__________ __________.

complex medium

Only__________ __________require high salt concentrations in order to grow.

obligate halophiles

Refrigeration will not kill most bacterial cells. Instead, it simply slows their metabolism and prevents them from __________.

reproducing.

A __________ medium is used to grow obligate anaerobes, while an __________medium is most often used for growing fastidious bacteria that have very specific nutritional requirements.

reducing;enrichment

__________ agar distinguishes lactose-fermenters from non-lactose-fermenters.

MacConkey

__________ remove wastes and add nutrients so that bacteria may remain in the log phase indefinitely.

Chemostats

Bacterial growth is defined as......

Increase in bacterial cell population.

Method of culturing microorganisms in which colony-forming units are separating from me another using a series of dilutions.

Pour-plate

A liquid nutrient -rich medium used for cultivating microorganisms.

Broth

Having only one otganism present.

Axenic

Dish filled with solid medium used in culturing microorganisms.

Petri plate

Microorganism requiring temperatures ranging from 20 degrees celcius to about 40 degrees celcius.

Mesophile

Sample of material taken from such sources as ponds , soil or air and tested for the presence of microorganisms.

Environmental specimen

An organism that uses oxygen for a final electron acceptor.

Aerobe

Increase in size of a microbial population in which the number of cells doubles in a fixed interval of times.

Exponential (logarithmic) growth

Plant pigment that acts as an antioxidant.

Carotenoid

Microorganism requiring cold temperatures (below 20 degrees Celsius)

Psychrophile

Long term storage of cultures at temps ranging from -50 degrees Celsius to -95 degrees celsius.

Deep-freezing

Test tube containing agar media that solidified while the tube was resting at an angle.

Slant tube

Microorganism that acquires electrns from organic sources.

Organotroph

Culturing medium of which the exact chemical composition is known.

Defined medium (synthetic medium)

Removal of water from a frozen culture or other substance by means of vacuum pressure, used for the long term preservation of cells and food.

Lyophilization

A single cell or group of related cells that produce a colony.

Colony-forming unit (cfu)

The conversion of atmospheric nitrogen to ammonia.

Nitrogen fixation

Culturing medium containing substances that either favor the growth of particular microorganisms or inhibit the growth of unwanted ones.

Selective medium

An organism that cannot tolerate oxygen.

Anaerobe

Phase in a growth curve in which organisms are adjusting to their environment.

Lag phase

Microorganism requiring acidic Ph.

Acidophile

Free of microbial contamination.

Sterile

Microorganism that cannot tolerate oxygen AnD uses a final electron acceptor other than oxygen.

Obligate anaerobe

Element required in very small amounts for microbial metabolism.

Trace element

Visible population of microorganisms living in one place;an aggragation of cells arising from one single parent cell.

Colony

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