Microbiology 208 Module 11

An alkalophile bacteria may grow in a human stomach.

False

Which of the following bacteria have an affinity for the heart valves?

Streptococcus mutans

Which of the following are mismatched?

Hyperthermophiles : no water

A sample placed into fresh medium is initially in the (lag/log/stationary) phase of microbial growth in most instances.

lag

The generation time of bacterial cells is shortest during the ________ phase.

log

Which of the following terms is likely to describe optimal growing conditions for Streptococcus mutans?

mesophile

You inoculate two tubes of liquid culture media with 100 bacterial cells and incubate one tube at 15° C and the other at 35° C. After 18 hours, there are 100 bacteria/ml in the 15° C tube and 996,000 bacteria/ml in the 35° C tube. You conclude that this species is a:

mesophile

A Staphylococcus species is found to grow best at 30oC. Which temperature group best describes this species?

mesophiles

You isolate a pure culture and determine that its CHARACTERISTICS are as follows. It GROWS optimally at 28°C. It will SURVIVE at temperatures from -70°C to +35°C. Its pH OPTIMUM for growth is 7.2. It was originally ISOLATED on the surface of strawberry jam. You might correctly CONCLUDE that this microbe is a(n) __________.

mesophilic aerobe that resists plasmolysis when sugar concentration is high.

What would the colony growth on a nutrient agar plate look like if you were to take a psychrophilic bacteria culture and put it in a 35oC incubator?

no growth

Determine whether the following enzymatic reactions are anabolic or catabolic and place them within the correct bin.

Anabolic Reaction= Ammonia is added to glutamate to form glutamine Four amino acids are linked together to form a tetrapeptide Ribose and inorganic phosphate are bonded to form a nucleotide base A uracil base is added to an mRNA strand by RNA polymerase Catabolic Reaction= Starches are digested into individual glucose molecules Glucose is broken down into two pyruvates

What does the term facultative anaerobe mean?

Facultative anaerobes can grow with or without oxygen. More growth is evident when oxygen is present.

A turbidity meter can be set to distinguish between living and dead cells.

False

During the lag phase, the bacterial cells are dormant and metabolically inactive.

False

The more fastidious a species of bacteria is, the greater its ability to grow in both a rich nutrient broth and a limited-nutrient, chemically defined broth.

False

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

Forty-eight cells

How long does it take for the daughter cells from one round of replication to replicate themselves?

No time is required -- they are ready to divide immediately after DNA replication and separation of the daughter cells is complete if conditions are right.

Assume that Staphylococcus aureus grows on nutrient agar with up to and including 15% (w/v) NaCl, while Escherichia coli cannot grow on nutrient agar with more than 10% (w/v) NaCl. What does this mean?

Some kinds of bacteria can grow at higher concentrations of NaCl than others.

Which organism is most likely to be responsible for the boils?

Staphylococcus aureus

You want to isolate a new obligate thermophilic bacterial species. Where is the best place to look?

a thermal hot spring

Which of the following is an example of a biofilm?

bacteria growing in plaque

Bacteria naturally prefer company instead of solitude for growth. Examples of this kind of communal growth pattern can be found everywhere, from surfaces of the teeth and the intestines, to the surface of a slimy rock in the lake, to the thick floc that clogs water pipes. These examples of communal bacterial growth are known by what name?

biofilm

S-S agar inhibits gram-positive bacteria. On this medium, bacteria that ferment lactose produce red colonies and bacteria that do not ferment lactose produce colorless colonies. This medium is:

both selective and differential.

Campylobacteri bacteria are grown with a Campy-Pak that produces 5% carbon dioxide and 15% oxygen. This bacterium is a(n):

capnophile

Which bacteria would have a culture growth spread throughout the broth culture?

the aeroteolerant Enterococcus faecalis

If growing a new bacteria culture for testing cellular metabolism, which phase would be best to take the bacteria from?

the logarithmic phase

You inoculate two tubes of liquid culture media 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/ml in the 37° C tube and 1,568,000 bacteria/ml in the 55° C tube. You conclude that this species is a:

thermophile

Which one of the following is not a characteristic of prokaryotes?

use mitosis

A spectrophotometer can measure the amount of light transmitted (T) or absorbed (A) through a test tube of a bacterial culture to determine culture density and therefore can calculate growth.

True

Agars can be used to select for growth of certain types of bacteria and then allow for you to identify the different bacteria that can grow on the plate. These agars may be considered both selective and differential.

True

Escherichia coli colonies on eosin-methylene blue agar will have a characteristic green metallic sheen that other gram-negative bacteria will not have.

True

Which of the following would you expect to be a function of MacConkey agar? Mark all that apply.

-Change the color of some organisms based on their metabolic characteristics -Inhibit the growth of certain bacteria

The Lake of the Ozarks is a human-made lake, so it collects runoff from coal strip-mining, fertilizers, resort wastewaters, and septic drainages. The average lake temperature is between 10∘C and 21∘C. Consider the physical requirements for growth and multiplication that would allow fecal coliforms to "blossom" in the Lake of the Ozarks. Which of the following would accurately describe these organisms?

-Facultative halophiles -Psychrophiles -Mesophiles

In addition to physical requirements, bacterial growth and multiplication also entails chemical requirements. Which of the following statements would accurately describe chemical requirements and conditions associated with growth in the Lake of the Ozarks environment? Select all of the following statements that are true regarding fecal coliforms in the Lake of the Ozarks.

-Fecal coliforms will likely contain enzymes to counteract toxic oxygen forms. -Fecal coliforms will need to acquire trace elements for growth in the lake environment. -The lake environment will support the growth of facultative anaerobes.

Use of moist heat can control microbial growth in many circumstances, but heat-sensitive items and those susceptible to moisture cannot be sterilized in this manner. Which of the following correctly describes a method of physical control used to control microbial growth on or in such items?

-Filtration is the passage of a liquid or a gas through a screenlike material with pores small enough to retain microorganisms. A vacuum is typically used to force the liquid through the mesh, and then the sterile liquid or gas is collected in a sterile container on the other side. -Nonionizing radiation, such as UV light, has a wavelength longer than that of ionizing radiation. The wavelengths of UV light are absorbed by cellular DNA in organisms directly exposed to the light. -Desiccation is a process that removes water from microorganisms, leaving them unable to grow or reproduce, but still viable. -Osmotic pressure is a process that uses high concentrations of salts and sugars to preserve food.

Botulism food poisoning is a preventable illness if special precautions are taken during food preparation. In this case, what could Sue have done to prevent the outbreak of botulism?

-Sue noticed that the pressure cooker was malfunctioning during the canning process. She should have fixed the instrument, borrowed a properly working one, or purchased a new pressure cooker. -Sue could have boiled the food for at least 10 minutes before serving it to her family members.

Which of the following is an example of microbial control?

-Sue washes off the vegetables before serving them in a meal. -Sue uses bleach to clean the kitchen counters. -Mary places leftovers in the refrigerator after the meal.

Sodium nitrate and sodium nitrite are added to many meat products, such as ham, bacon, hot dogs, and sausage. These additives help to prevent the growth of Clostridium botulinum by inhibiting certain iron-containing enzymes of the organism. This is an example of chemical food preservation. Which of the following correctly describes a method of chemical control used to control microbial growth?

-Surface-active agents, or surfactants, decrease surface tension among molecules of a liquid. -Phenolics exert antimicrobial activity by injuring lipid-containing plasma membranes, which causes the cellular components to leak out of the cell. -Alcohols exert their action by denaturing proteins and dissolving lipids.

What aspects of biofilm formation and the interaction of bacteria within the biofilm would allow for the survival of the bacteria in the presence of the sanitizing solutions?

-The matrix of the biofilm aids in retention of nutrients and sequestration of the bacteria from environmental stresses such as chemical sanitizers. -Quorum sensing within the biofilm allows bacteria to respond to other bacteria and alter their enzyme expression. -Formation of a biofilm may allow for the survival of the bacteria that are at the base of the biofilm, farthest away from any chemicals found within the environment.

The hospital and the local health department have identified a single brand of ice cream that all four of the patients consumed within the last few days. Part of your job is to determine whether the ice cream could support the growth of the bacterial contaminant. You know that the ice cream is high in sugar and other organic compounds, so the bacteria would have the nutrients required for cellular metabolism; however, the ice cream is produced and maintained at low temperatures and stored at freezing or below freezing temperatures. Can bacteria or any organisms grow at these extremely low temperatures? When introduced into a new niche, bacteria may evolve by altering their proteins and cellular membranes to adapt to the new temperature. Environmental temperatures are nothing more than available heat, which for a cell system is the addition (hot temperatures) or removal (cold temperatures) of outside energy to an enzymatic reaction. As temperatures increase, the addition of energy will speed up enzymatic reactions until the point at which the additional heat energy begins to interfere with the hydrogen bonds holding the protein structure of the enzyme together. Once the enzyme loses its structure, all activity is lost. The same will occur with the lipid bilayer that forms the cell's membrane: increased movement of the phospholipids will result in leakage out of the cell. At the opposite end of the temperature spectrum, reduced temperatures slow down enzyme activity and lipid movement in the membrane. The question you are stuck with is whether or not there are any bacterial pathogens that can grow in such cold temperatures.

1. A bacterium with increased cholesterol in its cytoplasmic membrane to maintain membrane fluidity at extremely low temperatures would probably fall in the psychrophile class of bacteria. 2. A bacterium that can be found growing in a hot spring would be considered a thermophile. 3. A bacterium that is a common cause of human infections but is also part of our microflora would have to be in the mesophile class of bacteria. 4. The thermophile bacteria have evolved to grow and excel in temperatures that denature most protein and kill most organisms.

Isolation and Cultivation of the Bacteria

1. Bile salts in MacConkey agar allow for the agar to be selective for the growth of enteric Gram-negative bacteria over Gram-positive bacteria. 2. An agar that allows for the distinction of bacteria based on metabolism would be considered differential. 3. A blood agar plate contains sheep red blood cells and allows for the determination of hemolytic capabilities for all bacteria that grow on the agar. This would make this type of agar differential. 4. An agar that uses a high salt concentration to limit the growth of one type of bacteria over another would be considered selective. 5. The differential aspect of MacConkey agar allows for the determination of which bacteria are lactose fermenters and which are not. 6. EMB agar uses lactose and two dyes that allow it to be differential between the blue-black colonies of E. coli and the pinkish colonies of all other enteric bacteria. 7. An agar that uses the dye in crystal violet agar suppresses the growth of Gram-positive bacteria. This agar would be considered selective. 8. If an agar contains a dye or pH indicator in the presence of a sugar, it is generally considered differential for those bacteria that may ferment the sugar over those that cannot.

How many colony forming units (CFUs) are in the original tube per mL if you ran a serial 10 dilution and counted 230 colonies on the 1:100,000 dilution plate?

2.3x107

Put the following steps of bacterial replication in the correct order, starting from a parent cell. 1. Cell elongation 2. Septum formation 3. Chromosome replication 4. Separation of daughter cell

3, 1, 2, 4

If 32 colonies are on the plate of 1/10,000 dilution, then what would be the number of cells per ml in the sample?

320,000

A 100 μl sample containing 1000 bacterial cells/μl in log phase growth is added to 9.9 ml of fresh culture medium broth. Assuming no nutrients are in limited supply, and a generation time of 30 minutes, how many bacteria will be present in the entire broth culture after six hours?

4.096 × 108

You have identified the causative agent of the illnesses as Listeria monocytogenes and have laboratory data to support your conclusion. Now you will need to determine the bacterial load of the pathogen within the samples collected. You'd like to know whether the illness is caused by a low level exposure (low bacterial numbers) or a high level of exposure (high bacterial numbers). You will use serial dilutions and plate counts to quantify the number of bacteria in your sample. By using a "serial 10" dilution method, each new tube of diluted bacteria will be 10 times more diluted than the previous tube. A sample of each of these dilutions can then be plated, and the resulting colony forming units counted to yield an estimate of the number of bacteria in your sample. You count 50 colony-forming units on the fourth plate that corresponds to the 10-4 dilution tube. How many bacteria would you estimate to be in the original sample?

5 x 105 bacteria per mL

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

6

You inoculate a glass of milk with three mesophilic bacterial cells, and then refrigerate the milk at 7° C. How many bacteria will be in the milk after five generations?

96

What is a boil?

A boil is a red lump in the skin that may be warm and painful to the touch. It is a localized accumulation of pus and tissue debris.

Which of the following best explains why the pressure cooker is so important in the canning process?

A pressure cooker utilizes steam to create a higher-pressure environment that allows the food to cook at higher temperatures than normal. The higher temperatures kill most contaminating microbes and endospores and therefore effectively sterilize the food.

In microbiology lab, you make three different culture plates: one general purpose plate, one selective media plate, and one differential media plate. Unfortunately, you forget to label the different plates, so you do not know which is which. To determine the identity of each plate, you inoculate it with two different strains of laboratory bacteria. Which of the following results would indicate the plate you used was the general purpose media?

Both organisms would grow equally well.

Which of the following organisms is an obligate anaerobe?

Clostridiumi (Aerobic growth -, Anaerobic growth +, Catalase -)

Why is Daniel underweight?

Daniel is not eating much, because it hurts to chew and swallow.

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

Disappearance of nuclear envelope

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

Molecular oxygen

What does halophilic mean?

It means the organism is "salt loving".

During which stage in the growth curve is the number of cells dying greater than the number of cells dividing?

Logarithmic decline phase

What does the term mesophile mean?

Mesophiles grow well at body temperature.

Which step of binary fission is the reason for genetically identical daughter cells?

Replication of the bacterial chromosome

Which of the following types of media is designed to suppress the growth of unwanted bacteria and encourage the growth of desired microbes?

Selective media

What is meant by the term "final electron acceptor"?

The final electron acceptor in aerobes is oxygen, which accepts the electron and H+ after it has been passed by the cytochromes in oxidative phosphorylation.

Most types of bacteria have specific metabolic oxygen requirements. Whether a bacterium requires oxygen or not has a large effect on its physiology. For example, aerobic bacteria, which require oxygen for their metabolic processes, must be able to counter the highly reactive oxygen species such as singlet oxygen (1O2) or a superoxide radical (O2−) that result from reactions within the cell. Bacteria that lack this capability are generally considered anaerobic. Since anaerobic bacteria utilize molecules other than oxygen as their final electron acceptor, they must possess adaptations to facilitate their survival in environments without oxygen. A majority of bacterial species lie somewhere in between these two polar opposites in that they are facultative anaerobes or able to utilize oxygen but also capable of surviving without it. Some particularly specialized facultative anaerobes are microaerophilic and grow only in low concentrations of oxygen. What are the enzymes and their reactions that allow bacteria to grow in the presence of oxygen? Which of the following statements correctly summarizes the enzymatic reactions to reactive oxygen species?

Superoxide dismutase detoxifies superoxides and converts them into hydrogen peroxide and oxygen. Catalase then converts the hydrogen peroxide into water and oxygen.

Why would temperatures above or below the growth range of a bacteria affect the metabolism of the bacterial cell?

Temperatures affect enzymatic activity; too low and the activity is reduced, too high and enzymatic proteins may lose their shape and be destroyed.

What enables the copied chromosomes to separate during binary fission?

The chromosomes are attached to different parts of cell membrane, which elongates and thus separates the chromosomes.

Why is it sometimes harder to grow certain species of bacteria on chemically defined media than it is on complex media?

The complex media has a component required by the bacteria for growth that is not added into the defined media.

What was the MOST likely source of the family's botulism food poisoning?

The family consumed botulism toxin in the canned green beans.

What would happen if the septum did not form during binary fission?

The parent cell would now have two copies of the chromosome.

A obligate thermophilic bacterial species cannot cause an infection in a human being.

True

Starting with three cells, how many cells would result from three rounds of replication?

Twenty-four

What results when a single bacterium reproduces?

Two genetically identical daughter cells

In order 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 key difference between classification methods and identification methods is that classification methods are designed to:

determine evolutionary relationships of organisms.

In microbiology lab, you make three different culture plates: one general purpose plate, one selective media plate, and one differential media plate. Unfortunately, you forget to label the different plates, so you do not know which is which. To determine the identity of each plate, you inoculate it with two different strains of laboratory bacteria. After inoculation, you see that a particular plate has allowed both organisms to grow, but one has changed color. Which plate do you think this is?

differential media

Blood agar used to observe hemolysis or clearing around Streptococcus pyogenes colonies is an example of a/an:

differential media.

During log phase, bacteria are:

dividing at the fastest possible rate.

Sampling lake water for microscopic organisms is not as easy as it sounds when you want to both count and identify species. In a given water sample, your bacteria of choice can be rare or difficult to culture, particularly given the mixture of bacteria in a biofilm. Which of the following culture media would be best for growing fecal coliforms when they are relatively less abundant than other bacteria in the lake?

enrichment culture medium

Which of the following types of culture media would best be used by a veterinarian to grow any bacteria in a blood sample?

enrichment media

Cultures of the Lake of the Ozarks water samples were grown on enrichment media for identification. However, these organisms are present to some degree in all samples. An important question from a clinical perspective is whether or not there is a significant increase in the fecal coliform populations that would put people's health at risk. If you were part of the team investigating this outbreak, how would you best enumerate the fecal coliform threat?

filtration count culture

A facultative anaerobic bacteria species such as Escherichia coli will exhibit what characteristics when grown in a broth tube?

growth throughout the tube with the highest concentration at the top

An organism found at the bottom of the Dead Sea is most likely a ____________.

halophile and barophile

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

inward growth of membrane

The evolutionary history of a group of organisms is called:

phylogeny.

Bacteria require nitrogen for the synthesis of:

proteins

Bacteria that spoil food in the refrigerator are most likely:

psychrotrophs.

A medium that contains lauryl sulfate inhibits growth of gram-positive bacteria. This medium is:

selective

Which nutrient is responsible for the development of cavities in teeth?

sucrose