Micro study questions chapter 6

All of the following statements about culture media are accurate EXCEPT which one? Complex media are formulated from nutrient-rich whole food sources whose exact ingredients may not be known. Reducing media are complex media containing chemicals, such as thioglycolate, that combine with oxygen, creating an anaerobic environment. A chemically defined medium is specifically formulated, and each ingredient is known. Nutrient agar contains ingredients that combine with oxygen and remove it.

Nutrient agar contains ingredients that combine with oxygen and remove it. Correct. Nutrient agar is a complex medium formulated to cultivate a variety of organisms; it is not a reducing medium.

Shrinking of the cell's cytoplasm in response to osmotic loss of water is called _________.

PLASMOLYSIS

In a/an _________ , cells are added to melted agar and poured into a petri dish. (2 words)

POUR PLATE

A type of cell-to-cell communication that allows bacteria growing in biofilms to communicate and coordinate their activity is known as ___________________. (two words)

QUORUM SENSING

What is quorum sensing? the ability of bacteria in a biofilm to grow on selective media the ability of bacteria in a biofilm to communicate with each other and coordinate their activities the ability of bacteria in a biofilm to use inorganic nitrogen sources the ability of bacteria in a biofilm to sense O2

Quorum sensing allows bacteria in a biofilm to communicate and organize into a coordinated, functional community.

Salt agar tends to inhibit the growth of most organisms, except Staphylococcus. This is an example of a/an __________ media.

SELECTIVE

The _______ _______ ________ is the most common technique used to obtain pure cultures of microbes. (3 words)

STREAK PLATE METHOD

Which of the following characteristics is a hallmark of bacterial growth? Since the number of bacterial cells double after each round of replication, the number of cells rapidly increases. After several rounds of division, the genetic diversity of the bacterial population will be very diverse. 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 each round of replication, the number of cells rapidly increases.

Adding salts to a solution increases osmotic pressure and is used to preserve food. True False

TRUE

Cells growing in a rich medium will have a steeper log phase slope than will those growing in a nutrient-poor medium. True False

TRUE

During the stationary phase, bacteria continue to undergo binary fission. True False

TRUE

Psychrotrophic organisms are often responsible for food spoilage in refrigerated foods. True False

TRUE

All of the following are true of the plate count method except ________. involves cell plating and growth measures number of viable cells most commonly used method for assay of bacterial cell number dependable fast-completed in minutes

fast-completed in minutes

The ability of microbes to utilize N2 as a nitrogen source is called ___________.

NITROGEN FIXATION

Bacterial growth refers to an increase in the ________ of bacterial cells.

NUMBER

Which of the following terms are mismatched? extreme halophiles; 30% salt acidophiles; low pH hyperthermophiles; no water psychrophiles; 0°C extreme thermophiles; 100°C

hyperthermophiles; no water

During which phase of bacterial growth would you see cell dividing most rapidly? lag phase log phase stationary phase death phase

log phase

In which phase of the growth curve is the population doubling time fastest? stationary phase lag phase. log phase death phase logarithmic decline phase

log phase

What phase of the cell cycle is extended in a chemostat? stationary phase logarithmic decline phase death phase lag phase log phase

log phase

Blood agar used to observe hemolysis or clearing around Streptococcus pyogenes colonies is an example of a/an ________. enrichment media differential media isolation media reducing media selective media

differential media

Which of the following is NOT a step in bacterial cell division? cell elongation disappearance of nuclear envelope replication of the genetic material splitting apart of two new daughter cells

disappearance of nuclear envelope

During log phase, bacteria are __________. dividing at the fastest possible rate dying and dividing in equal numbers preparing to divide dying exponentially

dividing at the fastest possible rate

An organism that grows both in the presence and the absence of oxygen and uses oxygen when it is available is called a/an ________. aerotolerant anaerobe aerobe anaerobe microaerophile facultative anaerobe

facultative anaerobe

If a single bacterium replicated every 30 minutes, how many bacteria would be present in 2 hours?

16

If you begin with three cells, how many cells would you have after three rounds of division? 6 9 12 18 24

24

In a pour plate technique, 32 bacterial colonies are counted on the 10-2 dilution of milk. How many bacteria were in the original milk? . (Do not use scientific notation in your answer.)

3200

If 52 bacterial colonies grow on a nutrient agar plate inoculated with 1 ml of a 1:1000 dilution of hamburger, how many bacteria are in the original hamburger sample? 52 bacteria per g 520 bacteria per g 5200 bacteria per g 52,000 bacteria per g

52 x 1000 = 52,000

Assume that you inoculated potato salad with 10 bacterial cells and stored it at room temperature. After 3 hours, there are 640 cells. How many generations did the cells go through? 1 generation 3 generations 6 generations 12 generations

6 generations

An unknown organism grows at the top of a tube of thioglycolate broth. This organism is best described as a/an _______ for its oxygen requirements.

AEROBE

Which biosafety level features open laboratory bench tops, gloves, lab coat, and face/eye protection? BSL-3 BSL-2 BSL-1 BSL-4

BSL-2

Which level of biosafety (BSL) is appropriate for handling organisms that present the highest risk level for infection and the lowest success rate for prevention and treatment? BSL-3 BSL-2 BSL-1 BSL-4

BSL-4 labs, popularly known as "the hot zone," are used for handling highly dangerous microorganisms, which require extraordinary systems of containment. A BSL-4 lab is a sealed environment within a larger building and has an atmosphere under negative pressure, so that aerosols containing pathogens will not escape

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. The generation times of bacteria are different from species to species. You cannot determine the number of cells with a linear graph. The number of cells dividing is equal to the number of cells dying, which can be determined only by a logarithmic graph.

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

Bacterial reproduction occurs by what process? lysogeny binary fission meiosis mitosis

Binary fission

A bacterial medium contains chemicals that inhibit gram-positive bacteria and indicators so that bacteria that ferment lactose produce red colonies, and bacteria that do not ferment lactose produce colorless colonies. Such a medium is called __________. enriched selective differential both selective and differential

Both selective and differential

Through metabolism, pathogens often produce acids that interfere with their own growth. ________ are/is added to media to control pH changes. Growth inhibitors Buffers Salts pH indicators Oxygen

Buffers

The enzyme _________ catalyzes the conversion of peroxide to water and oxygen.

CATALASE

To look for bacteria that degrade petroleum, a culture medium containing crude oil, sodium nitrate, phosphate buffer, and magnesium sulfate is inoculated with soil. This medium is __________. chemically defined complex differential reduced

Complex cannot be chemically defined because crude oil does not have an exact composition

Aerotolerant organisms can grow in the presence of oxygen because their cell wall protects them from toxic products of oxygen. True False

FALSE

Candle jars work well for cultivating anaerobic bacteria. True False

FALSE

Microaerophiles do not require oxygen for growth. True False

FALSE

Turbidity, or cloudiness, of cell cultures measured by spectrophotometry is useful in detecting small amounts of microbial contamination in liquids. True False

FALSE

When the spread plate technique is used to inoculate culture media, some colonies form within the agar. True False

FALSE

n a direct microscopic count, dead cells are easily differentiated from live cells. True False

FALSE

You are testing the number of coliforms in a drinking water source. Which of the following test methods would be best to use? dry weight direct microscopic count filtration turbidity

Filtration allows a large quantity of water to be examined and an exact direct count of viable cells to be enumerated.

What do all of these bacteria have in common? Bacteria in the rumen of cattle and sheep Bacteria in a sewage treatment plant Bacteria growing in the middle ear in chronic otitis media Bacteria growing on the teeth in dental plaque The bacteria are all thermophilic. The bacteria are all obligate aerobes. The bacteria are all fermenters. The bacteria are all gram-positive. The bacteria are most likely growing in biofilms.

The bacteria are most likely growing in biofilms.

An unknown culture is assayed via the plate count method. After dilution of cells and incubation, no colonies are observed. Which of the following is not a possible explanation? The media did not support the growth of the microbes. There were no cells in the culture. The incubation conditions were incorrect. The wrong dilution was plated. The bacterial cells formed invisible colonies.

The bacterial cells formed invisible colonies.

Why do cells that are placed in fresh media not immediately enter logarithmic phase of growth? Cells are preparing to enter a dormant state for long-term survival. The number of cells that are made is equal to the number of cells that are dying, resulting in no net growth. Some cells are dying and must be eliminated prior to cell division The cells need to switch their metabolic state from a dormant one to an actively growing one.

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

Which of the following statements regarding biofilms is true? The microbes in biofilms can work cooperatively to carry out complex tasks. Fortunately, biofilms are not an issue that impacts human health. Biofilms occur in nature but rarely occur in human infections. The close proximity of microbes within a biofilm probably inhibits conjugation.

The microbes in biofilms can work cooperatively to carry out complex tasks. Correct This statement is true. For example, the digestive systems of ruminant animals, such as cattle, require many different microbial species to break down cellulose. Such microbes in a ruminant's digestive system are located mostly within biofilm communities.

You inoculate two tubes of liquid culture media with 100 bacterial cells and incubate one tube at 37 degrees Celsius and the other at 55 degrees Celsius. After 48 hours, there are 20,000 bacteria per ml in the 37-degree tube and 1,568,000 bacteria per ml in the 55-degree tube. You conclude that this species is a __________. hyperthermophile thermophile mesophile psychrophile

Thermophile

Which of the following represent a true statement about the resulting new daughter cells? They share characteristics of both parental cells. Four new daughter cells result from one parental cell. They are genetically identical to the parent. They are unable to divide.

They are genetically identical to the parent.

Members of the genus Clostridium display the following properties: Gram-positive bacilli Endospore formation Anaerobic growth Which of the following would be appropriate for the culture of members of this genus? blood agar plate in a candle jar blood agar plate in an anaerobe jar nutrient broth sodium thioglycolate broth both a blood agar plate in an anaerobe jar and sodium thioglycolate broth

both a blood agar plate in an anaerobe jar and sodium thioglycolate broth

During the lag phase, ________. cells are growing in number changes in pH occur cells are engaged in intense enzymatic activity cells are decreasing in number nutrients are depleted

cells are engaged in intense enzymatic activity

A culture medium consisting of agar, peptone, and beef heart extract is a/an ________. chemically defined medium selective medium differential medium complex medium enrichment medium

complex medium

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

death phase

Open Hint for Question 13 in a new window Which of the following is not a step in binary fission? cell elongation invagination of the plasma membrane replication of chromosomal DNA lysis of the existing cell wall cross-wall formation

lysis of the existing cell wall

Bacteria growing in and on the human body, including normal microbiota as well as pathogens, are classified as ________. mesophilic and acidophilic thermophilic and acidophilic mesophilic and heterotrophic thermophilic and halophilic mesophilic and halophilic

mesophilic and heterotrophic

Campylobacter bacteria are grown with a CampyPak that produces 5% carbon dioxide and 15% oxygen. This bacterium is __________. anaerobe capnophile microaerophile aerotolerant anaerobe

microaerophile

Which of the following is not a chemical requirement of all bacteria? sulfur carbon mineral elements nitrogen molecular oxygen

molecular oxygen

Bacteria that CANNOT grow in the presence of oxygen (O2) are called __________. facultative anaerobes aerotolerant anaerobes obligate anaerobes obligate aerobes

obligate anaerobes

Niacin, when added to a medium, would be considered a/an ________. electron carrier carbon source organic growth factor reducing agent enzyme cofactor

organic growth factor

Bacteria require nitrogen for the synthesis of ________. carbohydrates sugars proteins fatty acids lipids

proteins

An organism that you are studying grows at 4°C and at 25°C. However, it grows best at 20°C. This organism would be classified as a ________.

psychrotroph

Bacteria that spoil food in the refrigerator are most likely __________. mesophiles thermophiles psychrotrophs hyperthermophiles

psychrotrophs Organisms that grow best at approximately 20 degrees Celsius, which is refrigerator temperature, are referred to as psychrotrophs.

Clostridium can be cultured in an anaerobic incubator or in the presence of atmospheric oxygen if thioglycolate is added to the nutrient broth. The addition of thioglycolate makes the medium __________. differential reduced selective enriched

reduced When oxygen is removed, the medium is said to be reduced, and it is appropriate for anaerobic bacterial growth.

A medium containing chemicals to inhibit the growth of gram-positive bacteria would be called __________. differential reduced selective enriched

selective A medium that inhibits the growth of certain bacteria while permitting the growth of others is described as selective.

Martin Lewis agar is an enriched media (containing heated blood) designed for the growth of Neisseria gonorrhea. Antibiotics are added to suppress the growth of normal microbiota that may be found in patient specimens, yet permit the growth of Neisseria gonorrhea. This medium would best be described as ________. selective media differential media nutrient agar defined media reduced media

selective media

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

stationary phase

All of the following can be used to preserve bacterial cultures EXCEPT __________. storing cultures at room temperature (25 degrees Celsius) refrigeration freezing quickly and storing at -70 degrees Celsius lyophilization (freeze-drying)

storing cultures at room temperature (25 degrees Celsius) Cultures cannot be sustained long in the incubator. The medium becomes desiccated, and the bacteria use up the nutrients and produce waste products that will result in decline of growth.

Before bacteria can be identified, mixed cultures must be separated. What technique is used to separate bacteria and get individual colonies? differential media selective agar streak plate enriched media

streak plate Correct. The streak plate for isolation separates individual colonies.