Ch 6

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

Nitrogen agar containing ingredients that combine with oxygen and remove it.

An unknown organism grows at the top of a tube of thioglycolate broth. This organism is best described as a(n) ___ for its oxygen requirements.

Obligate aerobe - this organism is best described as an obligate aerobe for its oxygen requirements. Microbes that use molecular oxygen (aerobes) extract more energy form nutrients than microbes that of not use oxygen (anaerobes). they would grow best at the top of a tube of thioglycolate broth since most oxygen would be available in that area.

Instead of oxygen, ___ may utilize nitrate or sulfate as their final electron acceptors.

Obligate anaerobes -Obligate anaerobes are bacteria that are unable to use molecular oxygen for energy-yielding reactions. in fact, most are harmed by it. instead of oxygen, anaerobes may utilize nitrate or sulfate as their final electron acceptors.

Bacteria require nitrogen for the synthesis of ___

Proteins

___ organisms are often responsible for food spoilage in refrigerated foods.

Psychotroph - they grown daily well at refrigerator temperatures

An organism displays some growth at 4°C and at 25C. However, it grows best at 20°C. This organism would be classified as a ___.

Psychrotroph - Psychrophiles: -10-20 - Psychrotrophs: 0-30 - Mesophiles: 10-50 - Thermophiles: 40-70 - Hyperthermophiles: 65-110

Martian soil is inoculated into a glucose-containing medium. the radioactive form of carbon, 14C, is used in the glucose. After incubation for five days, which of the following would provide evidence suggesting that their is life on mars.

Radioactive carbon dioxide

Salt agar tends to inhibit the growth of most organism, except Staphylococci. This is an example of a(n) ___ medium

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 the may be found in patient specimens, yet permit the growth of Neisserai gonorrhea. this medium would best be describes as___

Selective media

During which phase of the cell cycle are bacteria dividing equal to bacteria dying?

Stationary phase

In a standard growth curve, what phase represents when the number of cells growing and dying are about equal?

Stationary phase

What is quorum sensing?

The ability of bacteria in a biofilm to communicate with each other and coordinate their activities.

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 most likely growing in biofilms

An organism that has peroxidase and superoxide dismutase but lacks catalase is most likely an

aerotolerant anaerobe

When a bacterial cell reproduces by splitting into two daughter cells, the process is called ___

binary fission

A bacteria medium contains chemicals that inhibit gram-positive bacteria and indicators so that bacteria the ferment lactose produce red colonies, and bacteria that do not ferment lactose produce colorless colonies. such a medium is called ___.

both selective and differential

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 ___

both selective and differential

Medium 1 is

both selective and differential

Through metabolism, pathogen often produce acids that interfere with their own growth. ___ are/is added to media to control pH changes.

buffers

During the lag phase, ___.

cells are engaged in intense enzymatic activity.

To look for bacteria that degrade petroleum, a culture medium containing crude oil sodium nitrate, phosphate buffer, and magnesium sulfate is insulation with solid. This medium is ___.

complex

A culture medium consisting of agar, peptone, and beed-heart extract is a(n)

complex medium

Blood agar used to observe hemolysis or clearing around Streptococcus progenies colonies is an example of a(n) ___

differential medium

During log phase, bacteria are ___

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(n) ___

facultative anaerobe

You are testing the number of coliform in a drinking water source. which of the following test methods would be best to use?

filtration

A media that has a pH indicator and high salt concentration can likely ___ the growth of most bacteria.

inhibit

Which of the following is NOT a characteristic of biofilms?

iron deficiency

In which phase of the growth curve is the population doubling time fastest?

log phase

Bacteria growing in and on the human body, including normal microbiota as well as pathogens, are classified as ___

medophilic and heterotrophic

Campylobacter bacteria are grown with a CampyPak that produces 5% carbon dioxide and 15% oxygen. this bacterium is ___

microaerophile - microaerophile are aerobic, they do require oxygen. however, they grow only in oxygen concentrations lower than those in air.

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

molecular oxygen

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

Bacteria that CANNOT grown in the presence of oxygen are called ___

obligate anaerobes

Niacin, when added to a medium, would be considered a(n) ___

organic growth factor

Given a list, be able to distinguish which is NOT a direct measurement of microbioal growth.

plate count, filtration, most probably number (mPN) method, direct microscopic count

in a(n) ___, cells are added to melted agar and poured into a petri dish.

pour plate

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 drum

reduced

Which of the following types of media would NOT be used to culture aerobes?

reducing media

A medium containing chemicals to inhibit the growth of gram-positive bacteria would be called ___

selective

Medium 2 is

selective

A medium containing layryl sulfate inhibits the growth of gram-positive bacteria. This medium is ___

selective - designed to suppress the growth of unwanted bacteria and encourage the growth of the desired microbes

There term trace elements refers to

small mineral requirements

All of the following can be used to preserve bacterial cultures EXCEPT ___.

storing cultures at room temperature (25°C)

Before bacteria can be identified, mixed cultures must be separated. what technique is used to separate bacteria and get individual colonies?

streak plate

All of the following are true of the plate count method EXCEPT that it ___.

takes less than 12 hours to complete. -usually 24 hours or more, for visible colonies to form.

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

the microbes in biofilms can work cooperatively to carry out complex tasks

Assume you inoculated 100 facultatively anaerobic cells onto nutrient agar and incubated the plate aerobically. you then inoculated 100 cells of the same species onto nutrient agar and incubated the second plate anaerobically. after incubation for 24 hours, you should have

the same number of colonies on both plates

You inoculate two tubes of liquid culture medium with 100 bacterial cells and incubate one tube at 37°C and the other at 55°C. After 48 hours, there are 20,000 bacteria per mL in the 37°C tubes and 1,568,000 bacteria per mL in the 55°C tube. you conclude that this species is a ___

thermophile

If 100 colonies are on a 1:1000 dilution plate, how many bacterial/mL were in the original sample?

100000

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

16

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

52,000 bacteria per gram

Assume that you inoculated potato salad with 10 bacterial cells and stored it at room temperature. After 3 hours, there are 640 cels. how many generations did the cell go through?

6 generations

Which one of the following temperature would you most likely kill a mesophile?

60°C

Which of the lines best depicts the log phase of Listeria monocytogenes growing in a human?

A line

Which biosafety level features open laboratory bench tops, gloves, lab coat, and face and eye protection?

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-4

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 cult of members of this genus?

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

Which of the lines best depicts the lot phase of a thermophile incubated at room temperature?

C line

Given a "recipe" for a specific culture medium, identify a complex or defined medium

Complex media: extracts and digest yeasts, meat or plants, chemical composition varies batch to batch. Purpose:growth of most chemoheterotrophic organisms. Chemically defined media: exact chemical composition is unknown. Purpose: growth of chemoautotrophs, and photoautotrophs , microbiological assays.

which of the following terms are mismatched? - Psychrophile - 0°C - Hyperthermophile - 0°C - Acidophiles - low pH - Extreme thermophiles - 100°C - Extreme halophiles - 30°C

Hyperthermophile - 0°C

The following steps occur during binary fission. What is the third step?

Inward growth of membrane

which of the following is NOT a step in binary fission?

Lysis of the existing cell wall

which of the following is NOT a method used for the direct measurement of microbial growth?

Turbidity