3.2: Staining of microscope slides and descriptions (2023)

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    Learning objectives

    • Distinguish between simple and differential points
    • Describe the unique characteristics of commonly used dyes
    • Explain procedures and name clinical applications of Gram stain, spores, acids, negative envelopes and flagella
    • What to describe about cells in the microscope

    Clinical Focus: Part 2

    Wound infections such as Cindy can be caused by many different types of bacteria, some of which can spread rapidly with serious complications. Identifying the specific cause is very important to choose a drug that can kill or stop the growth of the bacteria.

    After calling the local doctor about Cindy, the camp nurse sends a wound sample to the nearest medical lab. Unfortunately, because the camp is in a remote area, the nearest laboratory is small and poorly equipped. A more modern lab would probably use other methods to culture, grow, and identify the bacteria, but in this case the technician decides to mount the sample and view it under a bright-field microscope. In a wet holder, a small drop of water is added to the slide and a coverslip is applied to the slide to hold it in place before being placed under the objective.

    Under a bright field microscope, the technician can barely see the bacterial cells because they are almost transparent against the light background. To increase the contrast, the technician places an opaque light barrier over the device. The resulting dark-field image clearly shows that the bacterial cells are spherical and clustered, like grapes.

    Exercise \(\PageIndex{1}\)

    1. Why is it important to recognize the shape and growth patterns of cells in a sample?
    2. What other types of microscopy can be effectively used to visualize this sample?

    In their natural state, most cells and microorganisms that we observe under a microscope lack color and contrast. This makes it difficult, if not impossible, to identify important cellular structures and their distinguishing features without artificially processing samples. We have already mentioned some of the techniques using dyes and fluorescent dyes, and in this section we will discuss specific sample preparation techniques in more detail. In fact, several methods have been developed to identify specific microbes, cell structures, DNA sequences, or markers of infection in tissue samples under the microscope. Here we will focus on the most clinically relevant techniques.

    Sample preparation for light microscopy

    In clinical settings, light microscopes are the most commonly used microscopes. There are two basic types of slides used to view slides under a light microscope: liquid mounts and fixed slides.

    The simplest type of preparation is the liquid preparation, in which the sample is placed on a slide in a drop of liquid. Some samples, such as a drop of urine, are already in liquid form and can be placed on a slide using a dropper. Solid samples, such as scraped skin, can be placed on a slide before adding a drop of liquid to prepare a liquid mount. Sometimes the liquid used is simply water, but stains are often added to increase the contrast. After adding the liquid to the slide, a coverslip is placed on it and the slide is ready for examination under the microscope.

    The second method of preparing samples for light microscopy is fixation. "Fixing" a sample refers to the process of attaching cells to a slide. Fixation is usually achieved by heating (thermal setting) or chemical treatment of the sample. In addition to securing the slide to the slide, fixation also kills the microorganisms in the slide, stopping their movement and metabolism, preserving the integrity of their cellular components for observation.

    To fix the slide with heat, a thin layer of the slide is spread on the slide (called a smear) and then the slide is briefly heated over a heat source (Figure \(\PageIndex{1}\)). Chemical fixatives are often better than heating tissue samples. Chemical agents such as acetic acid, ethanol, methanol, formaldehyde (formalin), and glutaraldehyde can denature proteins, disrupt biochemical reactions, and stabilize cellular structures in tissue samples (Figure \(\PageIndex{1} \)).

    3.2: Staining of microscope slides and descriptions (2)

    In addition to fixation, staining is almost always used to color certain characteristics of the sample prior to light microscopic examination. Stains or dyes contain salts consisting of a positive and a negative ion. Depending on the type of dye, the positive or negative ion can be a chromophore (color ion). the other colorless ion is called the counterion. If the chromophore is a positively charged ion, the dye is classified as a basic dye. If the negative ion is a chromophore, the stain is considered an acid dye.

    Dyes are selected for staining based on the chemical properties of the dye and the observed sample, which determine how the dye will interact with the sample. In most cases, it is preferable to use a positive dye, a dye that will be absorbed by the cells or organisms being observed, adding color to objects of interest to make them stand out from the background. However, there are cases where it is beneficial to use a negative dye that is absorbed by the background but not by the cells or organisms in the sample. Negative staining creates an outline or silhouette of organisms on a colored background (Figure \(\PageIndex{2}\)).

    3.2: Staining of microscope slides and descriptions (3)

    Since cells normally have negatively charged cell walls, positive chromophores in basic dyes tend to attach to cell walls, causing them to stain positively. Thus, commonly used basic dyes such as basic magenta, crystal violet, malachite green, methylene blue, and safranin usually serve as positive dyes. On the other hand, the negatively charged chromophores in acid dyes are repelled by the negatively charged cell walls, making them negative colors. Commonly used acid stains include acid fuchsin, eosin, and rose bengal.

    (Video) Introduction to Histology, Staining, and Microscopy

    Some staining techniques involve applying only one dye per sample. others require more than one painting. In single staining, a single dye is used to highlight specific structures in a sample. A single stain usually makes all organisms in a sample appear to be the same color, even if the sample contains more than one type of organism. In contrast, differential staining distinguishes organisms based on their interactions with different dyes. In other words, two organisms in a different colored sample may have different colors. Differential staining techniques commonly used in the clinical setting include Gram stain, acid-fast stain, endospore stain, flagella stain, and capsule stain.

    Exercise \(\PageIndex{2}\)

    1. Explain why it is important to fix the specimen before viewing it under the light microscope.
    2. What types of samples should be chemically fixed instead of thermally fixed?
    3. Why might an acid dye react differently with a given sample than a basic dye?
    4. Explain the difference between positive stain and negative stain.
    5. Explain the difference between simple and differential staining.

    Stains in grams

    The Gram stain procedure is a differential staining procedure that involves several steps. It was developed by the Danish microbiologist Hans Christian Gram in 1884 as an effective method to distinguish between bacteria with different cell wall types and remains one of the most widely used staining techniques to this day. The steps of the Gram staining procedure are shown in the figure \(\PageIndex{3}\) and listed below.

    3.2: Staining of microscope slides and descriptions (4)
    1. First, crystal violet, the primary dye, is applied to the heat-fixed smear, giving all cells a purple color.
    2. Gram's iodine, a flavoring agent, is then added. A mordant is a substance used to set or fix stains or dyes. In this case, Gram's iodine acts as a scavenging agent that forms complexes with crystal violet, causing the crystal violet-iodine complex to accumulate and be trapped in thick layers of peptidoglycan in the cell walls.
    3. A bleaching agent, usually ethanol or an acetone/ethanol solution, is then added. Cells that have thick layers of peptidoglycan in their cell walls are much less susceptible to the bleaching agent. they usually retain the crystal violet dye and remain purple. However, the decolorizing agent more easily removes the dye from cells with thinner layers of peptidoglycan, rendering them colorless again.
    4. Finally, an additional remedy, usually safranin, is added. This stains discolored cells pink and is less noticeable in cells that still contain crystal violet pigment.

    Violet cells stained with crystal violet are referred to as Gram-positive cells, while red cells stained with safranin are Gram-negative (Figure \(\PageIndex{4}\)). However, there are several important considerations regarding the interpretation of Gram stain results. First, older bacterial cells may have damaged cell walls, making them appear Gram-negative, even though the species is Gram-positive. Therefore, it is best to use fresh bacterial cultures for Gram staining. Secondly, errors such as prolonged whitening time can affect the results. In some cases, most cells will appear Gram-positive while some will appear Gram-negative (as shown in \(\PageIndex{4}\)). This indicates that individual cells have been damaged or that the bleach has been left on for too long. Cells should be classified as Gram-positive if they are all from the same species and not from a mixed culture.

    In addition to various interactions with pigments and decolorants, the chemical differences between Gram-positive and Gram-negative cells have other clinically significant implications. For example, Gram staining can help clinicians classify bacterial pathogens in a sample into categories related to specific properties. Gram-negative bacteria are usually more resistant to some antibiotics than gram-positive bacteria. We will discuss this and other applications of Gram staining in more detail in later chapters.

    3.2: Staining of microscope slides and descriptions (5)

    Exercise \(\PageIndex{3}\)

    1. Explain the role of Gram iodine in the Gram staining process.
    2. Explain the role of alcohol in the Gram staining process.
    3. What is the color of Gram-positive and Gram-negative cells, respectively, after the Gram staining procedure?

    Clinical Focus: Part 3

    Viewing Cindy's sample under a dark-field microscope gave the technician several important clues to the identity of the microbe that caused the infection. However, more information is needed to make a definitive diagnosis. The technician decides to perform a Gram stain on the sample. This technique is commonly used as the first step to identify pathogenic bacteria. After the Gram stain procedure is complete, the technician looks at the slide under a bright field microscope and sees purple clusters of round, grape-like cells (Fig. \(\PageIndex{5}\)).

    3.2: Staining of microscope slides and descriptions (6)

    Figure \(\PageIndex{5}\): Cindy's sample (Source: edited by the American Society for Microbiology)

    Exercise \(\PageIndex{4}\)

    1. Are these bacteria Gram-positive or Gram-negative?
    2. What does this say about your cell walls?

    Acid-resistant dyes

    Rapid acid staining is another commonly used differential staining technique that can be an important diagnostic tool. Acid-fast staining is able to distinguish between two types of Gram-positive cells: those that have waxy mycolic acids in their cell walls and those that do not. Two different acid staining methods are the Ziehl-Neelsen technique and the Kinyoun technique. Both use carbolic fuchsin as the primary dye. The acid-resistant wax cells retain carbo-fuchsin even after the use of a bleaching agent (acid-alcohol solution). A secondary counterstain, methylene blue, is then applied to turn the anaerobic cells blue.

    The main difference between the two methods based on carbolic fuchsin is whether or not heat is used during the main dyeing process. The Ziehl-Neelsen method uses heat to inject carbolic fuchsin into acidic cells while the Kinyoun method does not use heat. Both techniques are important diagnostic tools because several specific diseases are caused by acid-fast bacteria (AFB). If AFB is present in the tissue sample, its red or pink color is clearly visible against the blue background of the surrounding tissue cells (Figure \(\PageIndex{6}\)).

    (Video) 2.1.1. Cell Structure a) Microscopy c) Staining f) Magnification and resolution

    Exercise \(\PageIndex{5}\)

    Why are acid dyes useful?

    The use of microscopy in the diagnosis of tuberculosis

    Mycobacterium tuberculosis, the bacteria that causes tuberculosis, can be detected in samples by the presence of acid-alcohol-fast bacilli. Often, a smear is prepared from the patient's sputum sample and then stained with the Ziehl-Neelsen technique (Figure \(\PageIndex{6}\)). If acid bacteria are confirmed, they are usually cultured for positive identification. Variations of this approach can be used as a first step to determine whethertuberculosisor other acidic bacteria, although samples from other parts of the body (such as urine) may contain othersmycobacteriaPolite.

    An alternative approach to determining its presencetuberculosisis immunofluorescence. In this technique, antibodies labeled with a fluorochrome are attachedtuberculosis, if it exists. Antibody-specific fluorescent dyes can be used to visualize mycobacteria under a fluorescence microscope.

    3.2: Staining of microscope slides and descriptions (7)

    Capsule staining

    Some bacteria and yeast have an outer protective structure called a capsule. Since the presence of the capsule is directly related to the virulence of the microbe (its ability to cause disease), being able to determine whether cells in a sample have capsules is an important diagnostic tool. The capsules do not absorb most basic dyes. Therefore, a negative staining technique (staining around the cells) is usually used to stain the capsules. The dye stains the background but does not penetrate into the capsules, which appear as a halo around the edge of the cell. The sample does not need to be heat fixed prior to negative staining.

    A common negative staining technique for detecting encapsulated yeasts and bacteria is to add a few drops of Indian ink or nigrosin to the sample. Other capsular dyes can also be used to negatively stain capsular cells (Figure \(\PageIndex{7}\)). Alternatively, positive and negative staining techniques can be combined to visualize the capsules: positive staining stains the cell body and negative staining stains the background but not the capsule, leaving a shell around each cell.

    3.2: Staining of microscope slides and descriptions (8)

    Exercise \(\PageIndex{6}\)

    How does negative staining help us visualize the capsules?

    endospore staining

    Endospores are structures produced inside certain bacterial cells that allow them to survive in harsh environments. Gram stain alone cannot be used to visualize spores, which are clearly visible when Gram stained cells are visible. Endospore staining uses two dyes to distinguish endospores from the rest of the cell. The Schaeffer-Fulton method (the most commonly used technique for spore staining) uses heat to introduce the primary dye (malachite green) into the spore. Washing with water discolors the cell, but the endospore retains a green stain. The cell is then stained pink with safranin. The resulting image reveals the shape and location of the spores, if present. Green spores will appear inside the pink germ cells or will separate completely from the pink cells. If there are no spores, only pink germ cells will be visible (Figure \(\PageIndex{8}\)).

    3.2: Staining of microscope slides and descriptions (9)

    It is important to define endosperm dyeing techniquesBacillusMClostridium, two types of spore-forming bacteria containing clinically important species. Including,B. anthracite(causing anthrax) is of particular interest due to fears that its spores could be used as an agent of bioterrorism.It is hardis a particularly important species responsible for the common nosocomial infection known as "C. miscellaneous."

    Exercise \(\PageIndex{7}\)

    Is endospore staining an example of positive, negative or differential staining?

    (Video) IB Bio 3.2 Chromosomes .9 - Karyogram; Visibility; Stains; Micrograph; Centromere position

    Eyelash coloring

    Flagella (singular: flagella) are tail-like cellular structures used for locomotion by some bacteria, archaea, and eukaryotes. Because they are so thin, prokaryotic flagella cannot normally be seen under a light microscope without a specialized flagella staining technique. Flagella staining thickens the flagella by first applying a fragrance (usually tannic acid, but sometimes potassium alum) to coat the flagella. then the sample is stained with pararosaniline (most common) or basic fuchsin (Figure \(\PageIndex{9}\)).

    3.2: Staining of microscope slides and descriptions (10)

    Although flagella staining is rare in a clinical setting, the technique is commonly used by microbiologists because the location and number of flagella can be useful for classifying and identifying bacteria in a sample. It is important to handle the sample very carefully when using this technique. Flagella are delicate structures that can be easily damaged or severed, making it difficult to accurately locate and count the flagella.

    Exercise \(\PageIndex{8}\)

    Does flagella staining show the actual size of the flagella?

    3.2: Staining of microscope slides and descriptions (11)
    3.2: Staining of microscope slides and descriptions (12)

    Preparation of samples for electron microscopy

    Samples for TEM analysis must have very thin sections. However, the cells are too soft to be finely cut even with diamond knives. To excise the cells intact, they must be embedded in a plastic resin and then dehydrated by a series of immersions in ethanol solutions (50%, 60%, 70%, etc.). Ethanol replaces water in the cells, and the resin dissolves in the ethanol and enters the cell where it solidifies. Thin sections are then cut using a specialized device called an ultramicrotome (picture \(\PageIndex{12}\)). Finally, the samples are attached to thin copper wires or carbon fiber mesh and painted - not with colored dyes, but with substances such as uranyl acetate or osmium tetroxide, which contain electrically condensed heavy metal atoms.

    3.2: Staining of microscope slides and descriptions (13)

    When samples are prepared for visualization by SEM, they should also be dehydrated with an ethanol series. However, they need to be even drier than needed for TEM. Critical point drying with inert liquid carbon dioxide under pressure is used to displace water from the sample. After drying, the samples are sputter coated, removing atoms from the palladium target with energetic particles. Sputter coating prevents samples from being charged by the SEM electron beam.

    Exercise \(\PageIndex{9}\)

    1. Why is it important to dehydrate cells before examining them under an electron microscope?
    2. Name the device used to create thin sections of slides for electron microscopy.

    Using microscopy to diagnose syphilis

    3.2: Staining of microscope slides and descriptions (14)

    The causative agent of syphilis ispale treponema, a flexible spiral cell (spirochete) that can be very thin (<0.15 μm) and correspond to the refractive index of the medium, making it difficult to visualize by bright-field microscopy. In addition, this species has not been successfully cultured in the laboratory on artificial media. Therefore, diagnosis depends on successful identification using microscopic techniques and serology (analysis of body fluids, often for antibodies to the pathogen). Because fixation and staining kill cells, dark-field microscopy is commonly used to study living specimens and visualize their movement. However, other approaches can be used. For example, cells can be coated with silver particles (in tissue sections) and observed under a light microscope. Fluorescence or electron microscopy can also be used for visualizationTrembling(Picture \(\PageIndex{13}\)).

    In a clinical setting, indirect immunofluorescence is often used for identificationTrembling.The unstained primary antibody binds directly to the surface of the pathogen, and the secondary antibodies "labeled" with a fluorescent dye bind to the primary antibody. Multiple secondary antibodies can be attached to each primary antibody, increasing the amount of dye associated with each.Tremblingcells, making them easier to locate (Image \(\PageIndex{14}\)).

    3.2: Staining of microscope slides and descriptions (15)

    Preparation and staining for other microscopes

    Fluorescence and confocal microscopy slides are prepared similarly to light microscopy slides, except that the dyes are fluorochrome. Stains are often diluted with liquid before being applied to the glass. Some dyes bind to the antibody, staining specific proteins in specific cell types (immunofluorescence). others can bind to DNA molecules in a process called fluorescent in situ hybridization (FISH), causing cells to stain depending on whether they have a particular DNA sequence. Sample preparation for two-photon microscopy is similar to fluorescence microscopy except that infrared dyes are used.

    Exercise \(\PageIndex{10}\)

    (Video) Why you should not show prepared slides to beginners and children 🔬

    What is the main difference between sample preparation for fluorescence microscopy and light microscopy?

    Cornella UniversityCase studies in microscopyoffers a series of clinical problems based on real events. Each case study guides you through a clinical problem using appropriate microscopic techniques at each stage.

    Microscopy and antibiotic resistance

    With the widespread use of antibiotics in medicine as well as in agriculture, microbes have evolved and become more resistant. Bacterial strains such as those that are resistant to methicillinS aureus(MRSA), which has developed high levels of resistance to many antibiotics, is an increasingly worrying problem, to the point that research is being conducted to develop new and more diverse antibiotics.

    Fluorescence microscopy can be useful to test the effectiveness of new antibiotics against resistant strains such as MRSA. In a test of a new antibiotic derived from marine bacteria, MC21-A (bromophene), scientists used the fluorescent dye SYTOX Green to stain MRSA samples. SYTOX Green is often used to distinguish dead cells from live cells using a fluorescence microscope. Living cells do not absorb the dye, but cells killed by the antibiotic absorb the dye because the antibiotic has destroyed the bacterial cell membrane. In this particular case, MRSA bacteria exposed to MC21-A actually looked green under a fluorescence microscope, leading the researchers to conclude that it is an effective antibiotic against MRSA.

    Of course, some argue that the development of new antibiotics will only lead to even greater microbial resistance, the so-called superbiotics, which can cause epidemics before new treatments are developed. For this reason, many healthcare professionals are beginning to be more discreet in prescribing antibiotics. Given that antibiotics were once routinely prescribed for common diseases without a definitive diagnosis, it is much more common for doctors and hospitals to conduct additional testing to determine if an antibiotic is necessary and appropriate before prescribing.

    A sick patient may reasonably object to this sensible approach to prescribing antibiotics. For a patient who simply wants to feel better as soon as possible, the potential benefits of taking an antibiotic may seem greater than the immediate health risks that may occur if the antibiotic is ineffective. But to what extent do the risks associated with the widespread use of antibiotics outweigh the desirability of using them in individual cases?

    Description of cells under the microscope

    Once the cells have been stained, the next step is to use a microscope to characterize them. You'll always be looking for cell shape, grouping, and display colors. These descriptions of cell morphology (shape and structure) are his microscopic observations. This is most commonly done with prokaryotes, and the tables below contain the appropriate names of shapes and groups to use.

    3.2: Staining of microscope slides and descriptions (16)

    Image \(\PageIndex{15}\): ("Coccus" thumbnail: modified from Janice Haney Carr, Centers for Disease Control and Prevention; "Coccobacillus" thumbnail: modified from Janice Carr, Centers for Disease Control Centers for Control and disease prevention; thumbnail of "Spirochetes": edited by Centers for Disease Control and Prevention)

    3.2: Staining of microscope slides and descriptions (17)

    Eukaryotic cells exhibit a wide variety of different cell morphologies. Possible shapes include spheroidal, ovoid, cuboid, cylindrical, flat, lenticular, spindly, disc, crescent, star ring, and polygonal (Figure \(\PageIndex{17}\)). Some eukaryotic cells are irregular in shape and some are capable of changing shape. The shape of a particular type of eukaryotic cell can be influenced by factors such as its basic function, cytoskeletal organization, viscosity of the cytoplasm, stiffness of the cell membrane or cell wall (if present), and physical stress exerted on it from the surrounding environment and/or neighboring cells.

    3.2: Staining of microscope slides and descriptions (18)

    Exercise \(\PageIndex{11}\)

    1. What are the correct names for the common shapes of bacterial cells?
    2. What are the correct names for common groups of bacterial cells?
    3. Why don't eukaryotic cells always have the same shapes and groups as bacterial cells?

    Main concepts and summary

    • Samples must be properly prepared for microscopy. This may includecoloring,claspand/or cutthin sections.
    • Various staining techniques can be used in light microscopy, includingGram staining, oxidative staining,capsule staining,endospore staining,Mflagella coloring.
    • TEM samples require very thin sections while SEM samples require sputtering.
    • Preparation for fluorescence microscopy is similar to preparation for light microscopy, except that fluorochromes are used.
    • Cells have many unique characteristics when viewed under a microscope. When recording observations, describe the shape, grouping, and color(s) of the cells.


    • Nina Parker (Shenandoah University), Mark Schneegurt (Wichita State University), Anh-Hue Thi Tu (Georgia Southwestern State University), Philip Lister (Central New Mexico Community College), and Brian M. Forster (Saint Joseph's University) with many tax-paying authors . Original content via Openstax (CC BY 4.0; free access athttps://openstax.org/books/microbiology/pages/1-introduction)


    What is microscope slide staining? ›

    Microscope Slide Staining Information. Microscope cell staining is a technique used to enable better visualization of cells and cell parts under the microscope. By using different stains, a nucleus or a cell wall are easier to view.

    What 3 things will you always remember when you do simple staining procedure? ›

    Simple Stain Procedure
    • Do one slide at a time.
    • Cover the smear with any of the basic dyes available to you.
    • You only need enough dye to cover the smear. The stain should not drip off the slide.

    What can staining of cells tell you when viewed under the microscope? ›

    Certain types of microscopy, like phase contrast microscopy help in this regard but the easiest way to see cells is to stain them. Different staining methods can be used to tell differences between two cells or to stain a specific cellular structure.

    What are the different types of microscope slide stain? ›

    Microscope Slide Stains
    • Iodine: Stains carbohydrates in plant and animal specimens brown or blue-black. ...
    • Methylene blue: Stains acidic cell parts (like nucleus) blue. ...
    • Eosin Y: Stains alkaline cell parts (like cytoplasm) pink. ...
    • Toluidene blue: Stains acidic cell parts (like nucleus) dark blue.

    What is the purpose of staining cells on a microscope slide quizlet? ›

    Staining allows for the visualization of bacterial cells because it increases contrast during microscopic imaging.

    What is the purpose of staining cells on a microscope slide blank? ›

    Stains are used to help identify different types of cells using light microscopes. They give the image more contrast and allow cells to be classified according to their shape (morphology). By using a variety of different stains, you can selectively stain different areas such as a cell wall, nucleus, or the entire cell.

    What are 3 examples of simple stains? ›

    The Simple Stain

    Some stains commonly used for simple staining include crystal violet, safranin, and methylene blue.

    What are the basic rules of staining? ›

    Some basic rules for staining

    1. Keep stains and solutions covered when not in use. 2. After the slides are removed from oven these should be cooled before being put in xylene.

    What are the steps of staining? ›

    The Gram staining process includes four basic steps, including:
    1. Applying a primary stain (crystal violet).
    2. Adding a mordant (Gram's iodine).
    3. Rapid decolorization with ethanol, acetone or a mixture of both.
    4. Counterstaining with safranin.
    Mar 16, 2022

    What information does a simple stain reveal about a cell? ›

    The simple stain can be used to determine cell shape, size, and arrangement. True to its name, the simple stain is a very simple staining procedure involving only one stain. You may choose from methylene blue, Gram safranin, and Gram crystal violet.

    What does a positive Gram stain look like under a microscope? ›

    Gram-positive organisms are either purple or blue in color, while gram-negative organisms are either pink or red in color. Bacilli are rod-shaped, while cocci are spherical.

    How does staining affect the appearance of a specimen? ›

    A simple stain will generally make all of the organisms in a sample appear to be the same color, even if the sample contains more than one type of organism. In contrast, differential staining distinguishes organisms based on their interactions with multiple stains.

    What are the 3 types of special staining? ›

    Special Stains
    • Massons Trichrome. The trichrome stain helps to highlight the supporting collagenous stroma in sections from a variety of organs. ...
    • Verhoff's Elastic Stain. ...
    • Reticulin Stain. ...
    • Giemsa Stain.

    What is the best stain for microscope slides? ›

    Methylene Blue is a popular alkaline stain used to view microscopic life in brilliant color. It helps make cells show up against their background, where their shape can help you determine what they are (their morphology).

    What is the purpose of staining a sample? ›

    Staining is used to highlight important features of the tissue as well as to enhance the tissue contrast.

    What is the purpose of staining quizlet? ›

    What is the purpose of Staining? to make the bacteria, which are otherwise nearly transparent, visible. What's another way of accomplishing fixing?

    What is an example of a simple stain? ›

    Some stains commonly used for simple staining include crystal violet, safranin, and methylene blue. Simple stains can be used to determine a bacterial species' morphology (cell shape) and arrangement (single, chains, clusters, etc.), but they do not give any additional information.

    What is a primary purpose for the use of stains in microscopy? ›

    A primary purpose for the use of stains in microscopy is the increase the (magnification/brightness/contrast) of a specimen. An integral part of serological testing is the use of a solution called (blood/plasma/antiserum) that contains antibodies.

    What is simple staining quizlet? ›

    Simple staining is a procedure where a single type of stain or dye is used to help visualize bacterial cell size, arrangement, and morphology, and make measurements, on the microscope. Bacterial cells appear transparent, but adding stains give color and contrast enabling one to observe the cells.

    When microscope slides are stained to show blood cells? ›

    What is a Blood Smear? A blood smear is a sample of blood that's spread on a glass slide which is treated with a special stain. In the past, all blood smears were examined under a microscope by laboratory professionals. Now automated digital systems may be used to help examine blood smears.

    What are the 3 stains used in microbiology lab? ›

    Thus, commonly used basic dyes such as basic fuchsin, crystal violet, malachite green, methylene blue, and safranin typically serve as positive stains.

    What are the 3 stains used in negative stain? ›

    Some suitable negative stains include ammonium molybdate, uranyl acetate, uranyl formate, phosphotungstic acid, osmium tetroxide, osmium ferricyanide and auroglucothionate. These have been chosen because they scatter electrons strongly and also adsorb to biological matter well.

    Why is staining important in microbiology? ›

    Staining is very useful for the following reasons: To make the microscopic semi transparent microbial cell visible. To reveal the size and shape of microorganisms. To demonstrate the presence of internal and external structures of microbial cells.

    What is the correct order of staining? ›

    1) Treatment with 0.5% Iodine solution. 2) Counter staining with safranin. 3) Treatment with absolute ethanol. 4) Staining heat fixed smear with crystal violet.

    What are the four steps of staining? ›

    The performance of the Gram Stain on any sample requires 4 basic steps that include applying a primary stain (crystal violet) to a heat-fixed smear, followed by the addition of a mordant (Gram's Iodine), rapid decolorization with alcohol, acetone, or a mixture of alcohol and acetone and lastly, counterstaining with ...

    What are the two main types of staining? ›

    • Types of staining techniques.
    • Simple staining.
    • Differential staining.
    • (Use of of single stain)
    • (Use of two contrasting stains)
    • Direct.
    • Indirect.
    • Separation.

    What are examples of staining? ›

    Sr No.Name of Indirect Staining Technique
    1.)Gram's Staining
    2.)Cell Wall Staining a.) Ringer's method b.) Dyar's method
    3.)Flagella Staining a.) Leifson's method b.) Loeffler's method
    4.)Spirochete Staining a.) Fontana's method b.) Becker's method

    What is the most important step in staining? ›

    The step that is most crucial in effecting the outcome of the stain is the decolorizing step.

    What are the types of simple staining? ›

    Simple staining can be of two types: simple positive staining and simple negative staining.

    What stain is used for cells? ›

    The methylene blue stain makes nuclei more visible although it stains both nuclei and cytoplasm; the eosin mainly colors the cytoplasm and cell membranes.

    What information do you gain by staining a sample? ›

    These stains are used for the identification of specific types of tissue and identification of abnormal tissue, so a subsequent biopsy can be more accurate in obtaining abnormal tissue.

    Are basic stains positive or negative? ›

    Basic stain is a positively charged dye; Acidic stain is a negatively charged dye. Basic stain is an indirect stain; Acidic stain is a direct stain.

    What do Gram-negative cells look like under a microscope? ›

    If the bacteria is Gram negative, it will lose the primary stain and take the secondary stain, causing it to appear red when viewed under a microscope.

    How do you read a Gram stain under a microscope? ›

    A Gram stain is colored purple. When the stain combines with bacteria in a sample, the bacteria will either stay purple or turn pink or red. If the bacteria stays purple, they are Gram-positive. If the bacteria turns pink or red, they are Gram-negative.

    How do you view a Gram stain on a microscope? ›

    To view a Gram stain:
    1. Mount the slide on the stage with the smear facing the objective lens; if the slide is upside down, you won't be able to focus at high magnification. ...
    2. Rotate the condenser turret to the bright field position ("O" position).
    3. Move the aperture diaphragm knob to the center position (moderate contrast).
    Feb 18, 2017

    What are the results and interpretation of simple staining? ›

    Simple staining Result Interpretation

    Bacilli and diplobacilli will appear in rod-shape and in purple color (crystal violet). Spirilla will appear in spiral-shaped and in purple color (crystal violet). Cocci will appear in spherical-shaped and in purple color (crystal violet).

    What is the appearance of stain in negative staining? ›

    Negative staining employs the use of an acidic stain and, due to repulsion between the negative charges of the stain and the bacterial surface, the dye will not penetrate the cell. In negative staining, the results yield a clear cell with a dark background.

    When a specimen is stained which characteristic of the image is improved? ›

    For this reason, many specimens are cut into very thin sections (ranging from 1-30 microns in thickness) and stained with chemical dyes to increase contrast and to differentiate between structures residing within the specimen.

    What is the most commonly used staining methods? ›

    Haematoxylin and eosin (H & E): Routine stain

    This is the most common histologic stain, used to differentiate different tissue structures. It also plays an important role in the diagnoses of various pathologies.

    What is the most common type of staining? ›

    Gram Stain. The Gram stain is the most common differential stain used in microbiology. Differential stains use more than one dye. The unique cellular components of the bacteria will determine how they will react to the different dyes.

    What are the 4 different types of differential stains? ›

    Differential staining methods include safranin-methylene blue stain (Baxby et al., 1984), Kinyoun (Ma and Soave, 1983), Ziehl-Neelsen (Henricksen and Pohlenz, 1981), and DMSO-carbol fuchsin (Pohjola et al., 1984), which all stain the oocysts red and counterstain the background.

    What stain is used for slides? ›

    The Most Common Stains Used

    Haematoxylin and eosin combined make up a common stain most histology labs use first. No doubt you're familiar with at least haematoxylin, which is sometimes used alone. Combining this with eosin helps bring better definition to tissues and cells using a specific color chart.

    What is the most common staining method for microscopy? ›

    The most common stain is the combination of hematoxylin and eosin or H&E for short. This image of a pancreatic duct was stained with H&E and the image on the right was stained with only hematoxylin. Hematoxylin is a positively charged basic dye and will stain negatively charged, structures purple or dark blue.

    What is the purpose of staining for the electron microscope? ›

    The stain absorbs electrons in much higher amounts than the surrounding medium. Therefore, different regions of the sample have different electron densities and can be differentiated easier in the resulting projections.

    What is purpose of staining? ›

    Staining is used to highlight important features of the tissue as well as to enhance the tissue contrast.

    What is simple staining in microbiology? ›

    Simple staining involves directly staining the bacterial cell with a positively charged dye in order to see bacterial detail, in contrast to negative staining where the bacteria remain unstained against a dark background.

    Is staining of the specimen required in an electron microscope? ›

    Staining is used in bright-field microscopy and not in electron microscopy because this type of microscopy provides a contrast that is based on the density of the organic substances within the specimen to be observed.

    Why is staining a slide important? ›

    The purpose of staining is to increase the contrast between the organisms and the background so that they are more readily seen in the light microscope.

    What is the best stain for a microscope? ›

    Methylene Blue is a popular alkaline stain used to view microscopic life in brilliant color. It helps make cells show up against their background, where their shape can help you determine what they are (their morphology).

    What is staining technique? ›

    Staining, in microbiology, can be defined as a technique which is used to enhance and contrast a biological specimen at the microscopic level. Stains and dyes are used to highlight the specimen at the microscopic level to study it at higher magnification for histopathological studies and diagnostic purposes.

    What are the three purposes of staining? ›

    To reveal the size and shape of microorganisms. To demonstrate the presence of internal and external structures of microbial cells. To distinguish between different types of microorganisms. To produce specific chemical and physical reactions.

    What are the two purpose of simple staining? ›

    The purpose of simple staining is to be able to distinguish between two cells and the background under the microscope. Example, staining the bacterial smear on the slide with a single reagent.

    What colors are the stained blood cells under the microscope? ›

    Once the blood smear is stained, the cells are visually inspected with a microscope. One of the most commonly used differential stains is the Wright-Giemsa stain, which stains red blood cells a pinkish-red color, and stains the nucleus and cytoplasm of white blood cells various shades of purple.

    How do you identify red blood cells under a microscope? ›

    Red blood cells are shaped kind of like donuts that didn't quite get their hole formed. They're biconcave discs, a shape that allows them to squeeze through small capillaries. This also provides a high surface area to volume ratio, allowing gases to diffuse effectively in and out of them.

    What are the staining techniques for light microscope? ›

    A variety of staining techniques can be used with light microscopy, including Gram staining, acid-fast staining, capsule staining, endospore staining, and flagella staining. Samples for TEM require very thin sections, whereas samples for SEM require sputter-coating.


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