CH 6 micro

A microbe reproduces by binary fission every 20 minutes under favorable conditions. If you started with one cell, how many bacteria would be present after 8 hours? View Available Hint(s) 220 or 1,048,576 cells 48 cells 224 or 16,777,216 cells 480 cells 212 or 4096 cells

2^24 or 16,777,216 cells

A bacterial population that has been growing for 15 generations began as a single cell. How many cells are present now? View Available Hint(s) 30 cells 1024 cells 3375 cells 32,768 cells

32,768 cells

A bacterial species has been determined to have a generation time of 30 minutes. If a microbiologist starts with an inoculum of 1000 cells/ml and wants to grow it to a culture of 1,000,000 cells/ml, approximately how long should the culture be incubated?

5 hours

Which of the following statements is NOT part of the biofilm formation process? A. The cells form a multicellular prokaryotic organism with organ-like structures. B. The matrix of the biofilm positions the cells to conserve digestive enzymes. C. Quorum sensing allows the microbes to respond to the density of nearby microbes. D. Cells attach to a substrate and each other with an extracellular matrix.

A. The cells form a multicellular prokaryotic organism with organ-like structures.

Which of the following types of media is INCORRECTLY paired? A. defined medium: includes components for which the exact chemical composition is not known B. differential medium: different bacteria utilize nutrients in different ways C. complex medium: contains nutrients from partial digestion of yeasts, beef, soy, or milk D. selective medium: favors the growth of some microbes and inhibits the growth of others

A. defined medium: includes components for which the exact chemical composition is not known

List these catabolic pathways—fermentation, anaerobic respiration, and aerobic respiration—in order of the most energy produced in the form of ATP to the least.

Aerobic respiration, anaerobic respiration, fermentation Fermentation pathways do not utilize the citric acid cycle or electron transport chains; they only obtain energy from glycolysis through substrate-level phosphorylation Aerobic respiration and anaerobic respiration obtain additional energy through substrate-level phosphorylation in the citric acid cycle as well as through oxidative phosphorylation in an electron transport chain. anaerobic respiration, inorganic molecules (or rarely organic molecules) are the final electron acceptors, and only part of an electron transport chain is used, releasing less energy than aerobic respiration

_________use a final electron acceptor other than oxygen.

Anaerobes

In order to store living cells, a scientist must slow down metabolism by lowering temperature. Which of the following examples is INCORRECTLY paired? A. refrigeration: short periods of time B. sub-zero freezing: long term; -10°C C. lyophilization: freeze and remove water using an intense vacuum; ice sublimates D. deep freezing: long term; -50°C to -95°C

B. sub-zero freezing: long term; -10°C Deep freezing and lyophilization are used for long term storage

What influences bacterial generation times? Shape of the bacterium Whether the bacterium is a pathogen or not Only physical conditions such as temperature Bacterial species, chemical conditions, and physical conditions

Bacterial species, chemical conditions, and physical conditions

Most unicellular microbes reproduce by a process called ________

Binary fission

What category of organisms acquire both energy and carbon from complex organic compounds?

Chemoheterotrophs

Which of the following is NOT associated with the streak-plate method of isolation? A sterile inoculating loop or needle is used. A solid medium is used in this technique. Colonies will be found growing at and below the surface of the medium. The purpose is to isolate colony-forming units (CFUs) from one another.

Colonies will be found growing at and below the surface of the medium.

Which of the following statements concerning nitrogen is FALSE? A. Nitrogen is essential for the production of amino acids and nucleotide bases. B. All cells can recycle nitrogen from their nitrogen-containing molecules. C. Rhiozobium and many cyanobacteria are examples of a few bacteria that fix nitrogen. D. Nitrogen is rarely a growth-limiting nutrient.

D. Nitrogen is rarely a growth-limiting nutrient

All of the following are drawbacks to the use of spectrophotometry in estimating microbial growth EXCEPT that __________. A.it cannot be used if there are fewer than 1 million cells per milliliter B. it cannot distinguish between live and dead cells C. it will underestimate the true number of cells if they are not uniformly in suspension D. it kills the organisms as they are being counted

D. it kills the organisms as they are being counted

Of the catabolic pathways: glycolysis, fermentation, anaerobic respiration, and aerobic respiration, which can proceed without molecular oxygen (O2) present?

Glycolysis, anaerobic respiration, and fermentation

An organism that can tolerate or even grow in the presence of high levels of salt is a(n) ____________

Halophile

What do you call a solution that contains higher levels of dissolved solids than does a cell's cytoplasm? Hypotonic Isotonic Osmotic Hypertonic

Hypertonic

Using the metabolic rate of an organism to estimate the number of cells in a sample is considered a(n) ____________method of measurement.

Indirect -- scientists can indirectly estimate the number of cells in a culture by measuring certain changes in the specimen

Lithotrophs are organisms that obtain electrons or hydrogen atoms from _________ molecules.

Inorganic

Which of the following does NOT happen above the maximum growth temperature of a microorganism? Lipids become too fluid. Membranes become rigid and fragile. Proteins become denatured. Hydrogen bonds break.

Membranes become rigid and fragile.

Which of the major macromolecules--lipids, carbohydrates, proteins, and nucleic acids--contain nitrogen atoms (N)?

Nucleic acids and proteins

A bacterial culture that grows only near the surface of a thioglycolate broth is an example of what type of organism?

Obligate aerobes

What type of organisms could spoil macaroni and cheese stored in a closed container in the refrigerator, but are unlikely to infect humans?

Psychrophiles

Which of the following statements accurately describes the culture medium necessary for growing an anaerobe like Clostridium tetani? View Available Hint(s) Reducing media Nutrient agar A selective medium A differential medium

Reducing media

A researcher wants to study a water-dwelling fungus, but his water samples also contain numerous bacteria that reproduce faster than the fungi. To enhance his studies, and inhibit the bacteria, he should use View Available Hint(s) Sabouraud agar. MacConkey agar. blood agar. trypticase soy agar.

Sabouraud agar.

If an environment is acidic, is its pH lower than, equal to, or greater than 7?

The pH is lower than 7.

Why would a thermophilic organism not be able to cause disease in humans?

Thermophilic organisms depend on high temperatures for their growth.

When organisms are exposed to temperatures higher than their optimum growth temperature, their proteins are permanently denatured.

True

Bacteria that are pathogenic for humans are usually classified as mesophiles.

True-- mesophiles grow at temperatures ranging from 20-40c and that includes the human body temperatures

Which of the following does NOT use an inorganic source of carbon as its sole source? a photoheterotroph a chemoautotroph and a chemoheterotroph a photoautotroph a chemoautotroph

a photoheterotroph

You have a culture of bacteria that grows slowly but equally well throughout the culture of media. In regards to oxygen tolerance, this indicates that these bacteria are

aerotolerant

Which of the following groups of microbes do NOT use oxygen as their final electron acceptor but can detoxify oxygen enough to live in its presence? obligate anaerobes facultative anaerobes microaerophiles aerotolerant anaerobes

aerotolerant anaerobes

where do autrophs and heterotrophs get their carbon

autotrophs --carbon dioxide heterotrophs--organic compounds

A microbe isolated from deep ocean troughs could best be characterized as a __________.

barophilic hyperthermophile

Most unicellular microbes reproduce by a process called

binary fission

A candle jar would be most useful in isolating which of the following? biofilms psychrophiles capnophiles fastidious microbes

capnophiles-- grow best in high concentrations if carbon dioxide and low levels of oxygen -- when the candle extinguishes it creates a ideal environment --ex: niesseria gonorrhoeae

_______- is an enzyme that converts hydrogen peroxide to water and molecular oxygen.

catalase

A machine called a(n) ____________removes wastes and adds nutrients to a microbial culture to postpone the onset of stationary phase.

chemostat-- typically want to keep specimens in the log phase because the bacterium are more susceptible to antimicrobial drugs and are best to gram stain because cell walls are in tact; a chemostat controls the amount of nutrient available and maintains a particular phase

Which of the following types of media are INCORRECTLY paired? complex medium: contains nutrients from partial digestion of yeasts, beef, soy, or milk defined medium: includes components for which the exact chemical composition is not known differential medium: different bacteria utilize nutrients in different ways selective medium: favors the growth of some microbes and inhibits the growth of others

defined medium: includes components for which the exact chemical composition is not known

Carbohydrate utilization broths, which are fermentation broths, are primarily in a category of culture media called View Available Hint(s) selective. enriched. agar media. differential media.

differential media.

Indirect methods of measurement

dry weight, metabolic activity, turbidity, spectrophotometer, molecular methods

A student is trying to grow a fastidious microbe in her lab. She should be using View Available Hint(s) fastidious media. enriched media. selective media. trypticase soy agar.

enriched media.

A culture method designed to increase small numbers of microbes to observable levels is known as a(n) _______________culture.

enrichment (selective medium)

Which of the following is NOT an advantage conferred on microbial cells by a biofilm? formation of microenvironments protection from environmental stresses ability to stick to a surface extension of the microbial growth phase

extension of the microbial growth phase

The most commonly used isolation technique is the pour-plate method

false-- streak plate method

t/f Direct methods of measuring microbial growth are more accurate than indirect methods.

false--Both of these types of methods are merely ways of estimating the actual number of microbial cells present.

Which of the following toxic forms of oxygen is IMPROPERLY paired with the detoxifying enzyme or molecule? View Available Hint(s) hydroxyl radical: peroxidase peroxide anion: peroxidase superoxide radical: superoxide dismutase peroxide anion: catalase

hydroxyl radical: peroxidase

Microbes in the __________ phase of the microbial growth curve are most susceptible to antimicrobial drugs. View Available Hint(s) lag death log stationary

log

During which phase of a microbial growth curve is the population growing fastest? Stationary phase Lag phase Log phase Death phase

log phase

Microbes have very narrow optimum temperature ranges. Which of the following classifications of microbes are most likely to cause human disease, based on their temperature requirements?

mesophiles -- thrive at human body temperatures

Plasmolysis can result from a change in which of the following? View Available Hint(s) pH osmotic pressure temperature hydrostatic pressure

osmotic pressure

Fermented foods such as sauerkraut or pickles are kept from spoiling by the effects of which of the following? hydrostatic pressure low oxygen levels temperature pH

pH

Which of the following could be an optimal pH for the growth of an acidophile? pH 3.0 pH 7.0 pH 8.5 pH 11.0

pH 3.0-- pH as low as 0.0

breaks down hydrogen peroxide without forming oxygen

peroxidase

A cell that uses an organic carbon source and obtains energy from light would be called a _____.

photoheterotroph--organic carbon source

Which of the following methods used to count microbes is correctly identified as direct or indirect? View Available Hint(s) dry weight--direct measurement filtration--indirect method plate count--direct measurement turbidity--direct method

plate count--direct measurement

What method of isolation involves a series of liquid dilutions? pour-plate Colony forming unit Petri plate streak-plate

pour-plate

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

proteins and nucleotides

Biofilms consist of several different organisms working in complex relationships. These organisms communicate with each other using what sort of chemicals? Streamers Quorum sensing molecules Plaque molecules Water channels

quorum sensing molecules

Some researchers develop a new bacterial medium that inhibits the growth of Gram-negative bacteria. Such a medium would be primarily classified as View Available Hint(s) selective. selective and differential. enriched. general purpose medium.

selective

What sort of media can be used to encourage growth of some organisms, while discouraging the growth of others? Complex media Differential media Selective media Defined media

selective media

A colony-forming unit is a __________. View Available Hint(s) commonly used isolation technique tool used to collect clinical specimens special type of growth medium single cell or group of related cells that gives rise to a colony

single cell or group of related cells that gives rise to a colony

The most commonly used isolation technique in microbiology laboratories is the __________. View Available Hint(s) pour-plate method streak-plate method enrichment culture viable plate count method

streak-plate method

Bacterial cultures go through lag phase because __________.

they are adjusting to their new environment by synthesizing new enzymes in order to use various nutrients

What type of clinical specimen is collected through the "clean catch" method? Skin Stomach Urine Blood

urine