MICROBIO LAB 1 REVIEW

What is the total magnification of a specimen if you are using a compound light microscope with the 40x objective lens? 4x 400x 40x 4000x

400x

Which of the following is useful for identifying Mycobacterium tuberculosis, the bacteria that cause tuberculosis? Acid-fast stain Simple stain Bacterial endospore stain Gram stain

Acid-fast stain

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. Acid-fast stain: turns acid-fast cells blue Bacterial endospore stain: a structural stain Negative stain: typically does not require heat or chemical fixation of the sample prior to staining Gram stain: turns Gram-negative cells purple

Acid-fast stain: turns acid-fast cells blue; Gram stain: turns Gram-negative cells purple

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

Anything smaller than 200 nm cannot interact with visible light.

The image shows the results of a staining method that differentiates between bacteria that have thick or thin layers of peptidoglycan in their cell walls. Match the statement to the correct answer located in the drop-down menu. name of the staining technique what color are positive bacteria stained? what color are negative bacteria stained? name the primary stain name the counterstain

-Gram stain -purple -pinkish-red -crystal violet -safranin

The image shows the result of a certain differential staining method that detects the presence of mycolic acid in a bacterial cell wall. Match the statement to the correct answer located in the drop down menu. name of the staining technique what color are positive bacteria stained what color are negative bacteria stained name the primary stain name the counterstain

-acid-fast stain -pinkish purple -blue -carbolfuchsin -methylene blue

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

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

The image shows the results of a structural staining method that can used to detect certain structures that can be found in bacterial species such as Bacillus anthracis and Clostridium tetani. Match the statement to the correct answer located in the drop down menu. name of the staining technique endospore stain what are the pink structures vegetative cells what are the green structures endospores name the primary stain malachite green name the counterstain safranin

-endospore stain -vegetative cells -endospores -malachite green -safranin

What is the indicated structure on this pictured microscope? (This image shows a compound microscope with an arrow pointing at the large knob located on the side of the microscope's main body frame) Condenser Coarse focus Condenser control Fine focus

Coarse focus

What is the indicated structure on this pictured microscope? (This image shows a compound microscope with an arrow pointing at the part of the microscope that is responsible for focusing a cone of light onto the specimen.) Lamp Brightness adjustment Condenser Stage

Condenser

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

Gram stain differences.

How does the Gram staining procedure differentiate between Gram-negative and Gram-positive bacteria? 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. It differentiates between Gram-positive versus Gram-negative bacteria by bringing out differences in cellular proteins. It differentiates between Gram-positive versus Gram-negative bacteria based on differences in cell wall rigidity. It differentiates between Gram-positive and Gram-negative bacteria based on cell wall composition.

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

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

It ferments lactose.

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

It is spreading out

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

It would produce hydrogen sulfide.

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

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

What is the indicated structure on this pictured microscope? (This image shows a compound microscope with an arrow pointing at a lens that is on a rotating nosepiece just above the specimen) (This image shows a compound microscope with an arrow pointing at the part of the microscope that is responsible for focusing a cone of light onto the specimen.) Ocular lens Condenser Magnifying lens Objective lens

Objective lens

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

Resolution

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

The drop in pH turns the indicator dye yellow.

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

The medium turns blue.

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

The objective lens

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. The simple staining method reveals information about cell shape and arrangement. The simple staining method requires only one dye. Simple staining typically involves heat-fixing the specimen smear prior to staining. The simple staining method uses a single acidic dye that stains the slide background.

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

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

They allow the researcher to visualize relationships between different bacteria.

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

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

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

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

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

Three

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

To recreate the image in the viewer's eye

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

Two

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

are the main methods used to identify unknown bacteria

The image shows the results of a type of structural staining method called a negative stain that uses the dye, crystal violet. What are the purple colored structures depicted by the arrows? [Be prepared to identify the clear area surrounding the purple structures] capsules endospores carboxysomes bacterial cells

bacterial cells

A thick, detectable, discrete polysaccharide layer located outside of the cell wall that protects bacteria from the host's immune system and allow pathogens to invade the body is called a/an __________. endospore inclusion capsule cyst

capsule

Lethal _____________-forming bacteria, such as Bacillus anthracis, can be used for bioterrorism. endospore capsule nitrate sulfide

endospore

Metabolically inactive (dormant) forms of bacteria that can survive harsh environmental conditions such as heat and UV radiation are called ____________. cysts endospores capsules inclusions

endospores

You observe gram-negative cells that aren't spherical in shape, but instead are rod-shaped. Use the information and the dichotomous key to identify the microoorganism. Propionibacteria gram-negative bacilli Mycoplasm Corynebacterium

gram-negative bacilli

When preparing a slide for bacterial staining, the _________________ step attaches the bacteria to the slide and kills the microorganisms. heat fixing mordant decolorization prolonged drying

heat fixing

____________________ oil prevents the scattering of light when viewing a sample using the 100x objective lens. adjusting compound immersion lens

immersion

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

minimize scattered light when the high-powered lens is used

The image shows the result of a differential staining method called the Gram stain. What information can be concluded concerning the circled (blue) cells? [Be prepared to know information concerning the pinkish cells] the cells are gram negative and have a thin layer of peptidoglycan the cells are gram positive and have a thick layer of peptidoglycan the cells are gram positive and have a thin layer of peptidoglycan the cells are gram negative and have a thick layer of peptidoglycan

the cells are gram positive and have a thick layer of peptidoglycan

You have a mixture of gram positive and gram negative cells in culture. You prepare a slide from the culture and gram stain it, but when observing the sample using oil immersion, all cells appear purple. What is the likely technical reason why only purple-colored cells are observed? you killed the cells during heat fixation you forgot to add immersion oil you forgot the decolorization step you forgot the mordant step

you forgot the decolorization step

You are viewing a specimen using the 100x objective, but the image is fuzzy. Assuming that the microscope is clean and functioning properly, what is the likely reason why the image isn't clear? you forgot to use immersion oil the slide is broken you denatured bacterial proteins during the heat fixation process you are using the wrong type of microscope

you forgot to use immersion oil

The image shows the result of a certain differential staining method that detects the presence of mycolic acid in a bacterial cell wall. What information can be concluded concerning the circled (blue) cells? [Be prepared to know information concerning the pinkish cells] they are acid-fast organisms that have mycolic acid in the cell wall they are non acid-fast organisms that have mycolic acid in the cell wall they are non acid-fast organisms that don't have mycolic acid in the cell wall they are acid-fast organisms that don't have mycolic acid in the cell wall

they are non acid-fast organisms that don't have mycolic acid in the cell wall