microbiology final

On mannitol salt agar, how can you distinguish between pathogenic staphylococci and non-pathogenic staphylococci?

Almost all pathogenic staphylococci will ferment mannitol, while most non-pathogenic staphylococci will not ferment mannitol.

What is a gram-variable result?

A gram-variable result means the organisms cannot be grouped as either negative or positive. They gram stain a mixture of pink and purple cells.

Why are acid-fast bacteria especially difficult to stain?

Acid-fast bacteria are difficult to stain because of their resistant cell wall. Their walls have mycolic acid, which makes the cells resistant to staining, but also makes them resistant to being discolorized once they have been successfully stained.

Why is it helpful to place a loopful of water on the slide before making a smear with a sample removed from a petri dish?

Adding the droplet of water dilutes the sample, which in turn makes it easier to spread the cells into a thinner smear.

Which of these culture media would you use to store aerobic bacteria?

Agar slant

Chloroplasts resemble prokaryotic cells in several ways. Which characteristic do chloroplasts and prokaryotes share?

Both have 70S ribosomes

How do capsules provide protection for bacterial cells?

Capsules can protect a bacterial cell from phagocytosis by white blood cells. Capsules make bacterial surface components more slippery, helping the bacterium to escape engulfment by phagocytic cells.

Chemically, why does the citric agar slant change from green to blue if an organism can utilize citrate as the sole carbon and energy source?

Citrate agar is used to test an organism's ability to utilize citrate as a source of energy. The bacteria metabolizes citrate, causing the ammonium salts to be broken down to ammonia, which increases alkalinity. The change in pH turns the bromthymol blue indicator in the medium from green to blue above pH 7.6.

Which of these medically important genera of bacteria produces endospores?

Clostridium Streptococcus Neisseria Mycobacterium

Which word refers to the visible growth of a single cell on a solid surface?

Colony

Which of these items should NEVER be adjusted when examining an object with the oil immersion lens?

Course focus adjustment Light dimmer Fine focus adjustment Mechanical stage

Where do you find the critical concentration on the petri plate? How does this relate to the minimal inhibitory concentration?

The critical concentration on the petri plate is the zone of inhibition, which is the area of media where bacteria are unable to grow, due to presence of a drug that impedes their growth. This relates to the minimal inhibitory concentration because if there is a "ring" or zone of inhibition, there has been no growth, even minimally, whatsoever.

What structure(s) of gram-negative organisms make them more resistant to crystal violet and bile salts than gram-positive organisms?

The gram-negative organisms have an external cell membrane made of lipopolysaccharides, which makes them more resistant to crystal violet and bile salts than gram-positive organisms.

Why must heat be used in the application of the primary stain during endospore staining?

The heat is not for removing the stain from vegetative cells, but for stianing the endospores.

What is the chemical reaction that is catalyzed by urease?

The hydrolysis of urea into ammonia and carbon dioxide is catalyzed by urease. Ammonia will then increase the pH.

Name four of the possible metabolic products being tested for in the methyl red test?

The methyl red (MR) test detects the production of sufficient acid during the fermentation of glucose (2 pyruvic acids). Acids: lactic acid, acetic acid, formic acid, propanic acid

Define minimal inhibitory concentration.

The minimum inhibitory concentration is the lowest concentration of a chemical which prevents visible growth of a bacterium or bacteria.

Which is NOT a structure used by microorganisms for locomotion?

contractile vacuole (axial filament, flagella,cilia)

Desiccation prevents microbial growth by

creating a hypertonic environment.

Which structure is present in eukaryotes but not in prokaryotes?

cytoskeleton

Alkylating agents kill by

denaturing proteins

What is the first thing you should do with the MRVP test tube?

divide the culture into two test tubes

During the stationary phase, bacteria are

dying and dividing in equal numbers

Which of these is NOT a characteristic of nearly all (>99%) coliform bacteria?

endospore forming

Which of these is NOT a layer in a bacterial endospore?

endosporium (cortex, spore coat, core)

Which of the following chemicals can kill endospores?

ethylene oxide

A cell that contains a single circular chromosome must also have a nucleus.

false

Bacterial cells with DNA damage die because they are no longer able to catalyze chemical reactions at the speed necessary to maintain life.

false

Bacterial populations are most concentrated during lag phase.

false

Chemotherapeutics such as the griseofulvin are effective antifungal agents because fungal cell walls contain chitin.

false

Fimbriae act as a virulence factor, meaning they decrease the likelihood that the bacterium will causes disease.

false

Freezing is an effective means of killing microbes.

false

Generation time is calculated when a population reaches stationary phase.

false

Gram-negative bacteria are the primary natural source of most antibiotics.

false

Microbes are most susceptible to antibiotics during the stationary phase.

false

Most viruses live independent of other organisms

false

Narrow-spectrum drugs kill only bacteria while broad-spectrum drugs kill both bacteria and viruses.

false

Some factors influencing the rate of microbial death include the number of microorganisms, the color of the material, the temperature, and the age of the chenicals.

false

Spectroscopy is a technique that is useful for measuring the concentration of dilute samples.

false

The attachment point for a virion that infects animals is located on the cell wall of the animal cell.

false

The bacterial flagellum is composed of the protein tubulin.

false

Thermophilic bacteria are responsible for most hemorrhagic fevers.

false

Trimethoprim is a chemotherapeutic that is typically used to treat tuberculosis.

false

Ultraviolet light kills by causing free radicals to be produced.

false

Unlike other organisms, the genetic material of all viruses is RNA.

false

Virions tend to be more resistant to sterilizing agents than endospores.

false

The purpose of the condenser is to

focus the light on the specimen Magnify the object Raise and lower the stage slowly Control the brightness of the light going through the specimen

Which of these types of antiviral chemotherapies prevents attachment?

fusion inhibitors

In the triple sugar iron agar medium, _______ is the sugar that is the least abundant.

glucose

What is the function of the flagella?

helps the cell move

Which antiseptic is an oxidizing agent?

hypochlorite bleach

Capnophiles grow best

in the presence of 2% carbon dioxide.

Which technique is used to sterilize heat labile solids such as foods and medicines?

ionizing radiation

What is the main reason that heat kills?

it causes proteins to denature

Bacteria smears are fixed before staining to

kill the sample. The acidic dye tends to attach to the glass slide The culture medium repels basic dyes.

What are the differential ingredients in MacConkey's agar?

lactose and neutral red

Lysozyme is more effective against gram-positive than gram-negative bacteria.

lysosome

Which organelles are involved in the breakdown of unwanted compounds within a cell?

lysosome and peroxisome

Which of these is NOT a functionally analogous pair between eukaryotes and prokaryotes?

lysosome — endospore

The ______________ holds the slide in place and is used to move the slide.

mechanical stage

Which of the following structures is part of the cytoskeleton in eukaryotes?

microtubules

Which of the following types of electromagnetic radiation will NOT sterilize?

microwaves

What is the purpose of the 7.5% sodium chloride concentration in mannitol salt agar?

It inhibits the growth of most bacteria.

Which of these is NOT a property of agar?

It is harvested from ironwood It produces a gel that traps a liquid culture medium and makes it solid It cannot be digested by nearly all microorganisms It solidifies at 44C

Which is NOT true about the glycocalyx?

It is stored within the central vacuole. (It is used to adhere to surfaces., It is composed of polysaccharide, It protects the bacterium from phagocytosis)

What is the purpose of the Fe2+ in the triple sugar iron agar?

It reacts with H2S to form a black precipitate

Which pair is mismatched?

Jenner microscopy Lister aseptic surgery Ehrlich chemotherapy Koch germ theory

Which organisms have cell walls predominantly made of mycolic acid?

mycobacteria

The nitrate reduction test is looking for the presence of what enzyme?

nitrate reductase

All viruses have

nucleic acids and capsids.

Which structure is composed of RNA and protein?

nucleolus

In what structure are the lipopolysaccharides (LPS) embedded?

outer membrane

What is the product of the catalase test that you observe in a positive test result but not in a negative test result?

oxygen

Safranin is a

simple / counter stain

Which membrane-bound structure is the site of lipid and steroid biosynthesis in eukaryotic cells?

smooth er

is the sole carbon and energy source available in the citrate test.

sodium citrate

___________ is the genus of bacteria that can grow on mannitol salt agar.

staphylococcus

Which technique using heat will yield a sterile product?

steam under pressure at 121°C for 15 min

Which enzyme catalyzes the reaction: 2O2-∙ + 2H+ → H2O2 + O2?

superoxide dismutase

Which of the following is the first step in biosynthesis of a +strand RNA virus?

synthesis of proteins from the +strand

What molecules connect the repeating disaccharides and act as the crossbridges in peptidoglycan?

tetrapeptides

A virion is

the dormant transmissible stage of a virus

What is the purpose of the decolorizer in the gram staining procedure?

to selectively remove stain from gram-negative cells

What is the purpose of the Kirby-Bauer disk diffusion susceptibility testing?

to test a pathogen's sensitivity to a drug

Fimbriae and pili differ in that fimbriae are

used for attachment while pili are used for conjugation.

All of the following antibiotics inhibit protein synthesis EXCEPT

vancomycin (tetracycline, erythromycin., lincosamide)

An infectious naked piece of RNA is a

viroid

Penicillin was considered a "miracle drug" for all of the following reasons EXCEPT that it

was the first antimicrobial compound. (has selective toxicity, inhibits gram-positive cell wall synthesis, doesn't affect eukaryotic class)

Which of these is NOT a property of the antimicrobial agent that affects its diffusion into the agar?

water concentration of the agar (diffusion properties of the antimicrobial agent, molecular weight of the compound, solubility in Mueller Hinton agar)

Which is a type of ionizing radiation?

x-rays

What are the colors of phenol red at pH 6.5 and pH 7.5, respectively?

yellow at 6.5 and red at 7.5

What reagent will you add to the nitrate reduction test if the test tubes do not turn red after adding the reagents Nitrate A and Nitrate B?

zinc powder

Nucleoside analogs work by

replacing normal nucleotides with less specific nucleotides

Name two of the metabolic products being tested for in the Voges-Proskauer test?

The Voges-Proskauer test determines if an organism produces acetylmethyl carbinol from glucose fermentation. Alcohols: acetoin, butanediol, ethanol, butanol

What advantage does the ability to sporulate give to bacteria?

The ability to sporulate gives bacteria the ability to survive hostile environments for long periods of time. (what type of environments)

If the phenol red in the urea broth is orange, what is the most likely pH of the solution?

7.1

The nucleolus resides just outside the nucleus and manufactures ribosomes.

False

Which of the following drugs is NOT used primarily to treat tuberculosis?

bacitracin (isoniazid, ethambutol, rifampin)

Most of the available antimicrobial agents are effective against

bacteria

Which reagent that you will use today contains potassium hydroxide?

barrits b

What is the type of reproduction found in most prokaryotes?

binary fission

A culture medium on which only halophiles grow and a yellow halo surrounds Staphylococcus aureus colonies while no halo surrounds Staphylococcus epidermidis is an example of a(n)

both selective and differential medium.

What is the best way to determine if gas has been produced in the fermentation process?

by the presence of a air bubble within the durham tube

What is the primary component of a bacterial capsule?

carbohydrates

Which of these lists of compounds are not potential waste products of fermentation?

carbon dioxide and water

Which pair is NOT correctly matched?

carboxysomes — carbon storage (metachromatic granules — phosphate storage, lipid inclusions — energy storage, magnetosomes — iron storage)

The antibiotic streptomycin binds to the 30S subunit of ribosome as shown in Figure 20.4. The effect is to

cause misreading of mRNA in 70S ribosome

β-lactam antibiotics damage which of the following bacteria structures?

cell wall

What type of organism are you most likely to isolate from a high altitude mountain lake?

psychrophile

Which of the following pairs is mismatched?

psychrophile — growth at -35°C (mesophile — growth at 30°C, hyperthermophile — growth at 87°C, psychrotroph — growth at 20°C)

Bacteria that spoil food in the refrigerator are most likely

psychrotrophs.

What is the color of a gram-negative cell after the mordant is washed off?

red

Which of these is NOT correct about a direct count?

It can distinguish between living and dead cells (Results can be determined quickly. Very little material needs to be prepared to perform a count. Morphological differences in organisms can help distinguish species.)

Which of the following enzymes is required for the replication of coronaviruses (+stranded RNA viruses)?

RNA-dependent RNA polymerase

How long will it take for the blue color to appear in a positive oxidase test?

15-30s

How long should the endospores be stained with malachite green?

2 - 3 minutes

The capsule stain should be rinsed off with __________.

20% COPPER (II) SULFATE

What is the chemical reaction that is catalyzed by the enzyme catalase?

2H2O2 → 2H2O + O2

What is the total magnification when the 40x objective and the 10x ocular are in place?

400 x

What is the size of the large subunit of bacterial ribosomes?

50s

Which organisms are NOT in the domain Eukarya?

Archaebacteria Algae Protozoa Fungi

Which structure is NOT present in all cells?

Endoplasmic reticulum (chromosome, ribosome, plasma membrane)

Which family of bacteria are the IMViC tests used to distinguish?

Enterobacteriaceae

Which organism is an aerotolerant anaerobe?

Enterococcus (Aerobic growth +, Anaerobic growth +, Catalase -

Agostino Bassi's discovery of a fungus in dead silkworms proved that microorganisms cause disease and death.

False

Endospores are a rare form of reproduction used only by archaebacteria.

False

Eukaryotic cell walls are made of peptidoglycan, a polymer of sugars and amino acids.

False

John Needham's experiment supporting spontaneous generation was flawed because air was not allowed to enter the container.

False

Microbes are not good for research because they require a great deal of time to grow.

False

Selective toxicity refers to compound that is harmful to a host but harmless to a pathogen.

False

Some examples of microscopic animals include amoebas, paramecia, and blue-green algae.

False

The decomposers in the environment are usually algae.

False

The germ theory of disease suggests that diseases are generated as a punishment from God for leading a sinful life.

False

The golgi apparatus is made of phospholipids and proteins, and it produces lipids and steroids for export out of the cell.

False

The mitochondria and the vacuoles are two organelles that contain their own chromosomes and ribosomes.

False

In the name Saccharomyces cerevisiae, Saccharomyces denotes the

Genus Species Specific epithet Family

Which of these is NOT an anatomical difference between gram-positive and gram-negative cells?

Gram -positive cells have mycolic acids and gram-negative cells do not. Gram-negative cells have an outer membrane and gram-positive cells do not Gram-positive cells have a thicker cell wall than gram-negative cells. Gram-negative cells have lipopolysaccharides and gram-positive cells do not.

Which is NOT an element of Koch's Postulates?

Resistance to host infection is due to previous contact with the pathogen The pathogen is grown in pure culture The pathogen causes the same illness when inoculated into a healthy individual The pathogen must be present in all diseased individuals but not in healthy individuals

Which of the following statements regarding cell walls is CORRECT?

Gram-positive cells have more peptidoglycan than gram-negative cells.

Why must you use heat when applying carbol fuchsin during the acid-fast staining technique?

Heat is used because some species of bacteria do not readily stain with simple stains. The heat drives the stain into the cell. Without heat, the waxy structures makes the cell wall hydrophobic and impermeable to most stains.

If the nitrate reduction test does not turn red after adding reagents A and B, what are two possible reasons for the lack of color?

If the nitrate reduction test does not turn red after the addition of the reagents, it can mean that the organism was unable to reduce the nitrate, or it could mean that the organism was able to denitrify the nitrate or nitrite to produce ammonia or molecular nitrogen.

What color is the capsule and what color is the vegetative cell?

In the Enterobacter aerogenes stain, the vegetative cell is stained a dark violet and the capsule is a clear ring.

Which bacteria were positive in the methyl red test? Which were positive in the Voges Proskauer test?

In the Methyl Red Test, Escherichia coli and my ID Bug, Enterococcus faecolis, tested positive. In the Vogues-Proskauer test, Enterobacter aerogenes and Enterococcus faecolis tested positive.

Which one of the following was the most significant difference in the experiments that resulted in Pasteur's proof of biogenesis being accepted over Needham's proof?

Microbes did not grow until the broth was inoculated The broth could support life Air was present Microbes were never grown in the broth

the acid-fast stain is used to differentiate what type of bacteria from all other bacteria?

Mycobacterium

Why does nigrosin not penetrate the bacterial cell?

Nigrosin is acidic

Name four potential products from the breakdown of nitrite (NO2-).

Nitrate, with the addition of a couple electrons (nitrate reductase), can be converted to nitrite. That nitrite in some bacteria, not all bacteria that can reduce nitrate to nitrite can do this, but some bacteria can convert nitrite to nitric oxide. Then, some can convert nitric oxide into nitrous oxide, and then potentially into nitrogen gas. Nitrite can be converted through a different pathway into NH4+, or ammonium.

Why is it recommended that fresh cells (< 24 hr.) be used for gram staining?

Older cultures contain more ruptured and dead cells. It is best to use fresh cells for gram staining because when gram positive bacteria become too old they can stain gram negative.

Microbes can be routinely found growing in all of these areas EXCEPT

Outer space Deep ocean trenches Hot springs Indoor air

Why should you be careful not to overheat the smear during the heat-fixing process?

Overheating can distort the form and structure (morphology) of the cells.

Lens that are ____________ will focus on the same plane when switching between objectives.

Parfocal

Eukaryotes that have cell walls made of cellulose, have plastids, and that harvest energy by photosynthesis, are placed in which kingdom?

Plantae Fungi Animalia Monera

Which of the following is NOT a domain in the three-domain system?

Prokaryotae Bacteria Eukarya Archaea

The end products of tryptophan degradation are indole and pyruvic acid. Why do we test for the presence of indole rather than pyruvic acid as the indicator of tryptophanase activity?

Pyruvic acid is intracellular, so therefore is not excreted into the medium. Indole is a waste product and can be detected in the medium: showing tryptophan activity.

What two materials are more common in the endospore than in the rest of the bacterial cell (see the American Society of Microbiology write up on the endospore stain protocol)?

The two most common general of bacterias that produce endospores are the genus Bacillus and the genera Clostridium/Clostridioides. Unlike vegetative cells, endospores have a permeability barrier, which makes staining more difficult. An endospore is structurally and chemically more complex than the vegetative cell it comes from. Externally, there are more layers, and as the layers form increases in calcium ions and the synthesis of dipicolinic acid impart traits that make the endospore chemically unique. Endospores are often called metabolically inert. Endospores are much more resistant than vegetative cells. Endospores have inner and outer spore coats - this is what gives them their high survival quality.

To increase contrast, what is typically done to slides before they are observed under a microscope?

They are stained.

Which is NOT a characteristic of prokaryotic cells?

They reproduce by mitosis. (They have a single circular chromosome, They have cell walls containing peptidoglycan, they lack a nucleus.)

Why are dense smears more difficult to interpret than thinner smears?

Thick smears are opaque, making the amount of light that can pass through decrease. This in turn makes it harder to visualize the morphology of isolated colonies or single cells under the microscope. It can be hard for the stain to penetrate through a thick smear.

Which is NOT a part of the study of microbiology?

Ticks Bacteria Fungi Viruses

Why is it important to allow a smear to air dry before fixing?

To prevent distorting the bacteria.

A membrane is a selectively permeable boundary made of polysaccharides and proteins.

True

A toxoid vaccine is made by deactivating a poison molecule and then injecting it into the host.

True

Chromosomes are composed of DNA that is wrapped around a protein scaffolding to reduce its length.

True

Eukaryotic cells are usually larger than prokaryotic cells.

True

Microorganisms normally inhabit parts of the human digestive and respiratory systems.

True

Porins are proteins located in the outer membrane that allow molecules to enter the periplasm.

True

Spontaneous generation is a hypothesis stating that some forms of life can arise from non-living things.

True

Staphylococcus aureus is a properly written scientific name.

True

The nuclear membrane, endoplasmic reticulum, and vesicles are all part of the endomembrane system of a eukaryotic cell.

True

Unlike eukaryotic chromosomes, bacterial chromosomes do NOT contain histone proteins.

True

Which of the following is NOT true about viruses?

Viruses use their own catabolic enzymes. (Virions contain a protein coat, Virions contain DNA or RNA but never both, Viruses use the anabolic machinery of the cell)

Why isn't it necessary to add the methyl red or other reagents aseptically?

We're looking at the waste products rather than growth of bacteria.

Which of the following is NOT a beneficial activity of microbes?

reducing crop yields so that food prices are higher producing antibiotics for use as medicines decomposing dead plant and animal material in the wild preserving food for humans

Which of these antiseptics works by both denaturing proteins and disrupting plasma membranes?

alcohols

Which bacteria contain isoprene units connected by ether linkages in their phospholipids?

archaea

Fungal diseases are difficult to treat because fungi

are anatomically and physiologically similar to human

Lysozyme is used during which stage of a bacteriophage's infectious cycle?

penetration

Viral envelopes are composed of which of the following molecules?

phospholipids

Which of these antifungal medications does NOT affect membranes?

polyoxin (allylamine, imidazole, polyene)

What is the function of the capsid in an enveloped virus?

protect the genetic material from nucleases

What genus of the Enterobacteriaceae is the urease test designed to help identify?

proteus

Retroviruses reside in cells as

proviruses

A slime layer is a loosely attached glycocalyx.

true

An organism that uses organic carbon as a carbon source is a heterotroph.

true

Autoclaving is the preferred method of sterilization unless the material is damaged by heat or pressure.

true

Bacterial plasma membranes differ from eukaryotic plasma membranes because eukaryotes contain sterols, e.g., cholesterol, in their membrane while bacterial cells do not.

true

Bisbiguanides and halogens are commonly used disinfectants because they are both highly efficient at killing microbes and safe to humans.

true

Cephalosporins are beta-lactam antibiotics that work by preventing bacterial enzymes from completing peptidoglycan synthesis.

true

Chemotherapeutic agents are by far the weakest of all the killing agents because they must be able to enter and not injure the host while destroying the pathogen.

true

Chemotherapeutics such as the tetracyclines inhibit ribosomes, hence, they prevent the production of proteins.

true

Enveloped and naked viruses differ by the presence or absence of a phospholipid bilayer, respectively.

true

Erythromycin affects 50S ribosomes; therefore, it is more effective against prokaryotic infections than eukaryotic infections.

true

Factors such as the age, mass, kidney health, and liver health of a patient must be considered when determining the correct amount of a chemotherapeutic agent that is used.

true

For the plasma membrane of thermophiles to function, it must contain more sterols than the membrane of a mesophile.

true

Generation time is best defined as the average time it takes cells to divide.

true

Microaerophiles require oxygen but can only grow where the oxygen concentration is lower than that in the atmosphere.

true

Microorganisms can be killed by being placed into temperatures above their maximum tolerance.

true

Moist heat kills more quickly and at lower temperatures than dry heat.

true

Nucleoside analogs can be used to treat both fungal and viral infections.

true

One antibiotic that mimics phospholipids is polymyxin.

true

Reducing media traps oxygen and promotes the growth of obligate anaerobes.

true

The bacterial cell wall is located immediately outside of the plasma membrane.

true

The correct order of the steps of the infectious stage are attachment, penetration, biosynthesis, maturation, and release.

true

The spikes of a virus are inserted into the host cell's plasma membrane during biosynthesis or maturation.

true

The usual areas of attack by killing agents are the cell wall, plasma membrane, proteins and nucleic acids.

true

Uncoating, i.e., the separation of the viral DNA from the capsid, is required by animal viruses that have an envelope.

true

Viral capsids are composed of small spheres of protein called capsomeres.

true

Viruses have two stages in their lifecycle: the virion and the infectious stages.

true

Viruses that do not have an envelope usually lyse the host cell to be released.

true

Which amino acid is being broken down in the indole test?

tryptophan