Ch. 1

The goal of the streak plate technique is to a. isolate a pure culture for study from a single colony. b. compare all of the colonies on a plate with a mixed culture. c. visualize all of the colonies on a plate from a pure culture. d. spread out a thick layer of bacteria and isolate the bacteria that outcompete the rest. e. compare how the shape, color and margin differ in colonies from a pure culture.

a. isolate a pure culture for study from a single colony.

Aseptic technique can be used for all of the following except a. sterilizing working surfaces. b. preventing healthcare-acquired infections. c. limiting the spread of diseases. d. keeping samples pure for studying. e. safely studying microbes in the laboratory.

a. sterilizing working surfaces.

Choose the FALSE statement(s) about the simple staining technique. To be marked correct, you'll need to select all false statements, as there may be more than one correct answer. a. The simple staining method reveals information about cell shape and arrangement. b. The simple staining method uses a single acidic dye that stains the slide background. c. The simple staining method requires only one dye. d. Simple staining typically involves heat-fixing the specimen smear prior to staining.

b. The simple staining method uses a single acidic dye that stains the slide background.

Why are flowcharts useful for dichotomous keys? a. They provide a map to the answer. b. They allow the researcher to visualize relationships between different bacteria. c. They allow the researcher to get the answer without having to do many tests.

b. They allow the researcher to visualize relationships between different bacteria.

Biochemical tests _________________. a. are used to determine rate of growth b. are the main methods used to identify unknown bacteria c. are the most effective way to determine bacterial shape d. are visualized using microscopes

b. are the main methods used to identify unknown bacteria

Immersion oil is required to _________. a. enhance the brightness of the light that illuminates the specimen b. minimize scattered light when the high-powered lens is used c. enhance specimen contrast to make viewing easier when the high-powered lens is used d. magnify a sample so that it is easier to see when the high-powered objective lens is used

b. minimize scattered light when the high-powered lens is used

The scientific method starts with a(n) a. observation. b. question. c. hypothesis. d. prediction. e. proposal.

b. question.

When do opportunistic pathogens tend to cause disease? a. when the host didn't wash with soap b. when the host is weakened c. after the host is already infected with a different pathogen d. when the host is young e. when the host is old

b. when the host is weakened

Why is a specimen smaller than 200 nm not visible with a light microscope? a. The lenses only go to 100 X magnification power. b. It is too easy to lose on the stage. c. Visible light is only good at wavelengths below 390 nm. d. Anything smaller than 200 nm cannot interact with visible light.

d. Anything smaller than 200 nm cannot interact with visible light.

Why can't prokaryotic species be defined as a group of similar organisms that could sexually reproduce together? a. Bacteria are all too different to be considered similar. b. They can be. c. The mating rituals of bacteria have not been studied enough. d. Bacteria reproduce asexually. e. We can't see them in enough detail to tell how similar they really are yet.

d. Bacteria reproduce asexually.

The first question in this dichotomous key addresses a. bacterial morphology. b. metabolic characteristics. c. oxygen tolerance. d. Gram stain differences.

d. Gram stain differences.

How does the Gram staining procedure differentiate between Gram-negative and Gram-positive bacteria? a. It differentiates between Gram-positive versus Gram-negative bacteria by bringing out differences in cellular proteins. b. It differentiates between Gram-positive versus Gram-negative bacteria based on differences in cell wall rigidity. c. It differentiates between Gram-positive versus Gram-negative bacteria by detecting the presence of mycolic acid in the cell wall of certain Gram-positive bacteria. d. It differentiates between Gram-positive and Gram-negative bacteria based on cell wall composition.

d. It differentiates between Gram-positive and Gram-negative bacteria based on cell wall composition.

Which of the following types of microscopy would be the best to provide information about 3-dimensional surface structures of a virus? a. Fluorescence microscopy b. Bright field microscopy c. Transmission electron microscopy (TEM) d. Scanning electron microscopy

d. Scanning electron microscopy

What happens to the light rays when they hit the specimen? a. They are focused into a small area towards the objective lens. b. They are diverted to the ocular lens. c. They are reflected, refracted, or absorbed by the specimen. d. They are absorbed by the stage.

c. They are reflected, refracted, or absorbed by the specimen.

All of the following are or can be produced by microbes except a. drugs like penicillin. b. food like chocolate. c. electronics like computer memory. d. biofuels like diesel. e. consumer products like biodegradable plastics.

c. electronics like computer memory.

You have been asked to lead a demonstration for the undergraduate microbiology lab course about the uses of negative staining when studying bacteria. A "negative" stain does not stain the bacterial cell itself but stains the space between cells. Under magnification, the acidic (negatively charged) nature of the stain will be repelled by the negatively charged bacterial cell wall and will leave the cell colorless in a stained background. Negative stains are used primarily to reveal the presence of negatively charged bacterial capsules; therefore, they are also called capsule stains. Encapsulated cells appear to have a halo surrounding them. The negative stain procedure does not require heat fixation, which limits any chances of alteration in bacterial cell shape and size. The bacterial suspension is added to a drop of stain, such as nigrosin or eosin, and drawn across the glass slide using a coverslip. Nigrosin staining-not safranin staining-of Klebsiella pneumoniae will allow for the visualization of the cell shape and the determination of the presence of a capsule. True of false?

True

A new project has come up in the core center - a researcher wants to study bacterial biofilms and will need you to document the process of biofilm formation. Bacterial biofilms are colonies of different species of bacteria that interact and allow the bacteria to grow in a new environment. Since this will be a mixed culture, you will need to use a staining protocol that allows for differentiation between bacteria based on cell wall properties. The Gram staining procedure uses a series of stains and alcohol decolorization to differentially color different species of bacteria that may be present in the growing biofilm. This differential colorization will allow for determination of bacterial morphology and give some insight into the bacterial cell wall composition. Put the following descriptions in order for the staining reactions in the cells of a bacterial smear during the Gram staining procedure. Dye molecules are rendered insoluble in presence of mordant; dye is rinsed away. Clear cells are stained a red or pink whereas the color of other cells remains unchanged. Cell wall of Gram-negative cells is broken down; Gram-positive cells remain intact. All cells are stained purple.

Unstained cells (start of process): 1. All cells are stained purple. 2. Dye molecules are rendered insoluble in presence of mordant; dye is rinsed away. 3. Cell wall of Gram-negative cells is broken down; Gram-positive cells remain intact. 4. Clear cells are stained a red or pink whereas the color of other cells remains unchanged. Stained cells (end of process).

Which of the following does not contribute to shifts in our normal microbiota? a. diet b. hormonal changes c. proper hand-washing technique d. our general environment e. age

c. proper hand-washing technique

Select the true statement(s) about a scientific name for an organism. To be marked correct, you'll need to select all true statements, as there may be more than one correct answer. a. A scientific name for an organism consists of two names. b. An organism's name may refer to its discoverer, the organism's shape and/or arrangement, or other distinct traits. c. The organism's phylum designation is described by its second name. d. An organism's taxonomic family is reflected in its first name.

a. A scientific name for an organism consists of two names. b. An organism's name may refer to its discoverer, the organism's shape and/or arrangement, or other distinct traits.

Which of the following is (are) mismatched? To be marked correct, you'll need to select all mismatched statements, as there may be more than one correct answer. a. Acid-fast stain: turns acid-fast cells blue b. Negative stain: typically does not require heat or chemical fixation of the sample prior to staining c. Bacterial endospore stain: a structural stain d. Gram stain: turns Gram-negative cells purple

a. Acid-fast stain: turns acid-fast cells blue d. Gram stain: turns Gram-negative cells purple

Why do electron microscopes have a better resolution versus light microscopes? a. An electron beam has a wavelength of about 1 nm, and resolution improves with smaller wavelengths. b. An electron beam has a wavelength of about 800 nm, and resolution improves with larger wavelengths. c. The lenses, knobs, and strength of the electron beam can all be highly controlled, which also explains why electron microscopes are so expensive. d. The lenses used to focus the electron beam are more adjustable than the ones in a light microscope. e. The additional steps necessary to prepare the sample for viewing provide the improved resolution.

a. An electron beam has a wavelength of about 1 nm, and resolution improves with smaller wavelengths.

Choose the false statement about aseptic culturing techniques. a. Aseptic technique is unnecessary in most labs because the majority of microbes are not pathogenic. b. Aseptic culture techniques require that any instrument that contacts a culture must be sterile. c. Aseptic culture techniques require that sterile media are used to grow microbes. d. Aseptic technique includes hand-washing.

a. Aseptic technique is unnecessary in most labs because the majority of microbes are not pathogenic.

Why is visualization not sufficient to properly identify bacteria? a. Bacteria have a limited set of shapes and many unrelated bacteria share the same shape. b. Bacteria have a limited set of shapes. c. Identification is only needed in clinical specimens. d. Not all bacteria can be seen with a light microscope. e. Many unrelated bacteria can share the same shape.

a. Bacteria have a limited set of shapes and many unrelated bacteria share the same shape.

Why is the unknown in this example not Pseudomonas? a. It ferments lactose. b. It can tolerate oxygen. c. It is a rod-shaped cell. d. It is a Gram-negative cell.

a. It ferments lactose.

How would the results be different if this organism was Salmonella? a. It would produce hydrogen sulfide. b. It would not tolerate oxygen. c. It would not ferment lactose. d. It would be a rod.

a. It would produce hydrogen sulfide.

What test result indicates that the unknown can utilize citrate as its sole carbon source? a. The medium turns blue. b. The medium turns pink. c. The culture becomes turbid. d. It turns the medium black.

a. The medium turns blue.

What is the hallmark of dichotomous keys? a. They consist of a series of paired statements, in which only one statement of each pair applies to a given organism. b. They only relate to biochemical processes of the cell. c. They are open-ended questions. d. They only relate to the shape of the cell.

a. They consist of a series of paired statements, in which only one statement of each pair applies to a given organism.

What is the role of the ocular lens? a. To recreate the image in the viewer's eye b. To adjust the wavelength of light c. To focus the light to a high intensity in a small area d. To do the bulk of the magnification

a. To recreate the image in the viewer's eye

Which of the following could be used as evidence for spontaneous generation? a. Uncovered meat will give rise to maggots. b. Shaking Pasteur's S-necked flasks did spoil the broth. c. Flies lay eggs that develop into maggots. d. Gauze-covered meat will not give rise to maggots. e. The broth in Pasteur's S-necked flasks did not spoil.

a. Uncovered meat will give rise to maggots.

Robert Koch helped establish the germ theory of disease by discovering that anthrax was caused by a bacterium. After he isolated and purified the same bacteria from several diseased animals, what would be the next step in order to show that this bacterium caused anthrax? a. introduce the bacteria into a new mouse to see if it established the same infection b. visualize the bacteria with an electron microscope c. find out if antibiotics treat the diseased animals d. culture the bacteria on Petri dishes e. perform physiological testing

a. introduce the bacteria into a new mouse to see if it established the same infection

Choose the true statement(s) about aseptic techniques. To be marked correct, you'll need to select all true statements, as there may be more than one correct answer. a. Aseptic techniques involve sterilizing surgical environments. b. Aseptic techniques are essential to keeping a microbial culture pure. c. Aseptic technique includes hand washing. d. Aseptic techniques reduce the incidence of healthcare acquired infections (HAIs).

b. Aseptic techniques are essential to keeping a microbial culture pure. c. Aseptic technique includes hand washing. d. Aseptic techniques reduce the incidence of healthcare acquired infections (HAIs).

Choose the false statement(s) about biofilms. To be marked correct, you'll need to select all false statements, as there may be more than one correct answer. a. Dental plaques is an example of a biofilm. b. Cells within a biofilm are described as "planktonic. c. "Biofilms may be made up of a single species of microbe. d. Biofilms make a microbe community difficult to eliminate with drugs.

b. Cells within a biofilm are described as "planktonic.

What is the role of lenses in microscopy? a. Lenses increase the contrast to determine structural differences in stained specimens. b. Lenses focus either light or electrons to create a magnified image of a specimen. c. Lenses are only used to magnify specimens that are smaller than whole red blood cells.

b. Lenses focus either light or electrons to create a magnified image of a specimen.

What color would Gram-positive bacteria be at the end of Gram staining if the decolorizing step was left out of the procedure? a. Blue b. Purple c. Green d. Pink

b. Purple

_________ is the ability to distinguish two distinct points as separate. a. Micrograph b. Resolution c. Total magnification d. Refractive index

b. Resolution

How is fermentation of lactose detected? a. The medium become turbid when exposed to air. b. The drop in pH turns the indicator dye yellow. c. The cells form a black precipitant. d. The acetoin produced turns the medium pink.

b. The drop in pH turns the indicator dye yellow.

In a typical brightfield microscope (seen in the animation), at which point does magnification begin? a. The condenser lens b. The objective lens c. The stage d. The lamp e. The ocular lens

b. The objective lens

Which of the following is NOT one of Koch's postulates of disease? a. The organism must be isolated from the infected host and grown in pure culture. b. The organism may cause a different disease in some infected individuals. c. The organism must be re-isolated from the inoculated diseased animal. d. The same organism must be present in every case of a disease.

b. The organism may cause a different disease in some infected individuals.

Select the true statement(s) regarding the scientific method. To be marked correct, you'll need to select all true statements, as there may be more than one correct answer. a. A conclusion is any data gathered using our senses or testing, whereas an observation interprets conclusions. b. In terms of science, theories that stand the test of time are eventually elevated to laws. c. A theory is a hypothesis that has been proven through many studies with consistent, supporting conclusions. d. A hypothesis is a prediction and is proposed as a potential answer to a question.

c. A theory is a hypothesis that has been proven through many studies with consistent, supporting conclusions. d. A hypothesis is a prediction and is proposed as a potential answer to a question.

Which of the following statements about bright field microscopy are true? a. Dark field, phase contract, and differential interference contract microscopy are better for observing dead samples. b. Bright field microscopy is able to see specimens without natural coloration. c. Bright field microscopy is the simplest and most common form of microscopy. d. Bright field microscopy is great for seeing living samples. e. Bright field microscopy has the sample appear as a brighter contrasting image on a dark background.

c. Bright field microscopy is the simplest and most common form of microscopy.

What is meant by light rays being divergent? a. It is coming together to a focused beam b. It is heading upwards c. It is spreading out

c. It is spreading out

________ predict what happens, while ________ explain how and why something occurs. a. Hypotheses; conclusions b. Theories; laws c. Laws; theories d. Observations; conclusions e. Observations; hypotheses

c. Laws; theories

________ showed that biogenesis is responsible for the propagation of life. a. Joseph Lister b. Antonie van Leeuwenhoek c. Louis Pasteur d. Carl Linnaeus e. Robert Hooke

c. Louis Pasteur

A student from one of the research labs is having trouble preparing a slide for examination and photographing. The bacterial slide that he has brought to you was prepared using a commercially purchased stain. He has asked for your help in determining what he is doing wrong so that he can change the lab protocols and continue on with his project. After examining the slide under oil immersion, you determine that no bacteria are present even though the student is able to show you the culture he used to make that slide that has visible growth in the liquid medium.Which of the following statements does NOT explain the fact that there are no bacteria present on the student's slide? Select all that apply. a. Insufficient heating of the slide did not drive out the thin layer of water and this resulted in minimal bonding between the bacteria and the glass slide. b. By not allowing a glass slide to completely air dry before heat fixation, the flame will cause the surrounding water to boil and this will damage the bacterial cell. c. Rinsing with alcohol during the washing step stripped the bacteria off the glass slide. d. Overheating during the fixation step boiled the water within the bacterial cells and resulted in the cells bursting.

c. Rinsing with alcohol during the washing step stripped the bacteria off the glass slide.

Which of the following is (are) mismatched? To be marked correct, you'll need to select all mismatched statements, as there may be more than one correct answer. a. Growth media: mixtures of nutrients to grow microbes b. Petri plates: solid media c. Streak plate technique: broth culture d. Pure culture: diverse colonies evident

c. Streak plate technique: broth culture d. Pure culture: diverse colonies evident

Select the true statement(s) about Pasteur's S-neck flask experiment. To be marked correct, you'll need to select all true statements, as there may be more than one correct answer. a. The experiment showed that bacteria may cause disease. b. The experiment showed that air could be sterilized to prevent contamination. c. The experiment proved biogenesis is responsible for the propagation of life. d. The experiment supported Pasteur's hypothesis that air contained contaminating microorganisms.

c. The experiment proved biogenesis is responsible for the propagation of life. d. The experiment supported Pasteur's hypothesis that air contained contaminating microorganisms.

You volunteer to help the student with his fixation technique and in choosing a proper stain for the project he is working on. After watching and helping the student correct any problems with his fixation technique, you now need to determine which stains to use. The single criterion for the project is to be able to determine cell shape and size in a pure broth culture after some treatments. No differentiation between cell types is required (i.e., Gram-positive or Gram-negative), so you want to convince the student that a simple stain would be his best option. The charged dyes used in simple staining will penetrate the bacterial cell and will be retained after rinsing the slide with water to remove surplus dye.Which staining procedure would be best to use to stain the slides required for this student's project? Why? a. Malachite green and heat will colorize the cell for easier visualization and is a simple process. b. Using crystal violet followed by a rinse and Gram's iodine will stain the cells a dark blue with large crystals. c. An acidic stain such as nigrosin will stain the cells a dark black coloration for easier viewing under the microscope. d. The positively charged methylene blue will be attracted to the negatively charged components of the cell wall and will be retained.

d. The positively charged methylene blue will be attracted to the negatively charged components of the cell wall and will be retained.

_________ is used to isolate individual colonies on a solidified agar surface. a. Aseptic technique b. Smear preparation c. Agar inoculation d. The streak plate method

d. The streak plate method

How many questions are needed in this dichotomous key to determine if the unknown is Bacteroides? a. Five b. Two c. Four d. Three

d. Three

How many answers are there to a question in a dichotomous key flowchart? a. Three 2. Any number of answers are possible. c. Four d. Two

d. Two

Normal microbiota are responsible for all of the following except a. producing vitamins for us. b. helping us digest foods. c. training our immune system. d. controlling epigenetic expression. e. impacting our moods and brain functions.

d. controlling epigenetic expression.

Minor mutations and/or gene transfers may lead to the development of a new______ and is a term that describes very closely related organisms that are slight genetic variants of one another. a. strand b. genus c. species d. strain

d. strain

________ bacteria can create sticky communities called ________, which are made up of single or diverse microbial species. a. Pathogenic; quorums b. Matrix; cavities c. Plaque; hangouts d. Infectious; flora e. Planktonic; biofilms

e. Planktonic; biofilms

Which of the following is not a microorganism? a. fungi b. archaea c. bacteria d. helminth e. mosquito

e. mosquito