Chapter 6: Microbial Growth and Nutrition

How many bacteria would you estimate to be in the original sample?

5 x 10^5 bacteria per mL

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.

Anabolic Reaction

A uracil base is added to an mRNA strand by RNA polymerase. Ammonia is added to glutamate to form glutamine. Ribose and inorganic phosphate are bonded to form a nucleotide base. Four amino acids are linked together to form a tetra peptide.

Which of the following is an example of a biofilm?

Bacteria growing in plaque

Selective Agar

Bile salts in MacConkey agar allow for the agar to be _________ for the growth of enteric Gram-negative bacteria over Gram-positive bacteria.

These examples of communal bacterial growth are known by what name?

Biofilm

Partially digested yeast, which has varying chemical elements, is added to a medium that has been created with exactly measured ingredients. What type of media has been produced?

Complex media

In a microbiology laboratory, what does culturing mean?

Culturing involves growing microbes in the lab.

Why is Daniel underweight?

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

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.

Differential

An agar that allows for the distinction of bacteria based on metabolism

Differential

EMB agar uses lactose and two dyes that allow it to be __________ between the blue-black colonies of E. coli and the pinkish colonies of all other enteric bacteria.

Differential

If an agar contains a dye or pH indicator in the presence of a sugar, it is generally considered___________ for those bacteria that may ferment the sugar over those that cannot.

Differential

The _________ aspect of MacConkey agar allows for the determination of which bacteria are lactose fermenters and which are not.

Differential

A medium designed to change color in order to indicate growth of certain types of bacteria would be considered a __________.

Differential medium

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

What does the term facultative anaerobe mean?

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

Which of the following statements would accurately describe chemical requirements and conditions associated with growth in the Lake of the Ozarks environment?

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

If you were part of the team investigating this outbreak, how would you best enumerate the fecal coliform threat?

Filtration count culture

Catabolic Reaction

Glucose is broken down into 2 pyruvates. Starches are digested into individual glucose molecules.

Which of the bacterial mixtures(s) grow as a biofilm?

Group 2

What does halophilic mean?

It means the organism is "salt-loving."

Label the parts of a typical microbial growth curve for bacteria inoculated into a closed vessel of liquid medium.

Lag Phase- bottom flat slope Log Phase- (+) slope Stationary- top flat slope Death Phase- (-) slope Time- x-axis Number of Live Cells- y-axis

Microbial growth is at its maximum rate during which of the following phases of the microbial growth curve?

Log phase

Which of the following techniques is most useful for measuring microbial reproduction when the density of a microbial population is very small?

Membrane filtration

A bacterium that is a common cause of human infections but is also part of our microflora would have to be in the __________ class of bacteria.

Mesophile

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

Mesophile

Which of the following represent the majority of pathogenic bacteria?

Mesophiles

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?

Mesophiles Psychrophiles Facultative Halophiles

What does the term mesophile mean?

Mesophiles grow well at body temperature.

Indicate the oxygen requirements of the microorganisms growing in each thioglycolate tube. The surface of the tube is exposed to oxygen and is aerobic. Oxygen concentration decreases with depth; the bottom of the tube is anaerobic.

Obligate aerobes- all near top of broth Obligate anaerobes- all near bottom of broth Facultative Anaerobes- mostly near top of broth Aerotolerant Anaerobes- spread throughout

What is a colony-forming unit?

One or more cells that give rise to an assemblage of identical cells

Which of the following types of organisms use an organic source of carbon?

Photoheterotroph

Nitrogen is a growth-limiting nutrient because cells need it to manufacture __________.

Proteins and nucleotides

A bacterium with increased cholesterol in its cytoplasmic membrane to maintain membrane fluidity at extremely low temperatures would probably fall in the _________ class of bacteria.

Psychrophile

A chemoheterotroph obtains its energy from __________ and its carbon from __________ sources.

Redox reactions Organic

An agar that uses a high salt concentration to limit the growth of one type of bacteria over another would be considered

Selective

An agar that uses the dye in crystal violet agar suppresses the growth of Gram-positive bacteria.

Selective

Bile salts in MacConkey agar allow for the agar to be _____________ for the growth of enteric Gram-negative bacteria over Gram-positive bacteria.

Selective

Because some target bacterial species are out-competed by others during growth on media, it is sometimes necessary to inhibit the growth of the competitors. What type of medium is specialized for this scenario?

Selective media

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

Staphylococcus aureus

Microbes in the __________ phase of the microbial growth curve are most susceptible to antimicrobial drugs.

Stationary

The goal of streaking for isolation is to spread an inoculum of bacteria thinner and thinner with each pass for the identification of individual colony-forming units. What action must be performed between each step to ensure this?

Sterilization of the loop must be performed

What is the purpose of using the streak plate method?

Streak plates lead a scientist toward a pure culture for identification or examination of a single bacterial strain.

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

Streptococcus mutans

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

Sucrose

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.

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. 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. Quorum sensing within the biofilm allows bacteria to respond to other bacteria and alter their enzyme expression.

A bacterium that can be found growing in a hot spring would be considered a ________

Thermophile

The ___________ bacteria have evolved to grow and excel in temperatures that denature most protein and kill most organisms.

Thermophile

Why might a hospital choose to use transport media to carry clinical specimens?

Transport media are designed to keep microbes stable until they can be inoculated into appropriate growth media.

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

Fermented foods such as sauerkraut or pickles are kept from spoiling by the effects of which of the following?

pH