Microbio Ch 6

Which of the following statements about culture media is FALSE?

Nutrient agar contains ingredients that combine with oxygen and remove it.

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

Psychotroph

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 there is life on Mars?

Radioactive carbon dioxide

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

Stationary phase

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

Streak plate

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.

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

a microaerophile

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

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 __________.

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.

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 inoculated with soil. This medium is __________.

complex

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

complex medium

Blood agar used to observe hemolysis or clearing around Streptococcus pyogenes 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

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

mesophilic and heterotrophic

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

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

Bacteria that CANNOT grow in the presence of oxygen (O2) are called __________.

obligate anaerobes

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

obligate anaerobes

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

organic growth factor

In a(n) __________, cells are added to melted agar and poured into a Petri dish.

pour plate

Bacteria require nitrogen for the synthesis of __________.

proteins

An organism displays some growth 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 __________.

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 __________.

reduced

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

selective

A medium containing lauryl sulfate inhibits the growth of gram-positive bacteria. This medium is __________.

selective

Salt agar tends to inhibit the growth of most organisms, 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 that may be found in patient specimens, yet permit the growth of Neisseria gonorrhea. This medium would best be described as __________.

selective media

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

storing cultures at room temperature (25°C)

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

takes less than 12 hours to complete

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 milliliter in the 37°C tube and 1,568,000 bacteria per milliliter in the 55°C tube. You conclude that this species is a __________.

thermophile

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 1 ml 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 cells. How many generations did the cells go through?

6 generations

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 culture of members of this genus?

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

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

Filtration

Which of the following terms are mismatched? Hyperthermophiles; 0°C Acidophiles; low pH Extreme thermophiles; 100°C Extreme halophiles; 30% salt Psychrophiles; 0°C

Hyperthermophiles; 0°C

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

Inward growth of membrane

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

Log phase

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

Lysis of the existing cell wall

Which of the following is NOT a chemical requirement of all bacteria?

Molecular oxygen

Which of the following statements regarding biofilms is true?

The microbes in biofilms can work cooperatively to carry out complex tasks.

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

Turbidity