Microbiology with Diseases by Taxonomy Chapter 4 Answers
Microbiology with Diseases by Taxonomy Answers
Microbiology with Diseases by Taxonomy Chapter 4 Answers 1CM
Gram staining is a method that is used to differentiate bacterial species into gram-negative and gram-positive. This method was developed by Hans Christian Gram.
This staining method differentiates bacteria by the physical and chemical characteristics of the bacterial cell walls.
In this method a primary stain, a mordent (iodine), decolorizer and counter stain is used. A gram-positive bacterium appears in purple-blue color while gram-negative appears in pinkish-red color after staining.
The concept map which includes all the above terms is shown below:
Microbiology with Diseases by Taxonomy Chapter 4 Answers 1CT
Miss M. did a Gram stain in her practical class and came home with green fingers, and a low grade.
M must have mistakenly used another stain instead of crystal violet for the primary stain. The stain she used might have been malachite green. Malachite green is usually used in spore staining but not in Gram staining.
The procedure of Gram staining is:
- A smear is made with culture on a glass slide.
- The smear is air dried and heat fixed.
- The smear is then flooded with the primary stain.
- After some time, the stain is washed off and the smear flooded with the mordant.
- The mordant is used to bind the primary stain to the cells.
- The mordant is washed off and the decolorizer used.
- After the decolorizer is washed off, the counter stain is used.
- The counter stain is washed off and the cells viewed under the microscope.
- If the cells are Gram positive cells, they are violet in color while Gram negative cells are seen in red color.
Microbiology with Diseases by Taxonomy Chapter 4 Answers 1FB
The magnification of an object depends on both magnifying power of ocular and objective lenses. Moreover, the total magnification observed is the product of magnifying power of two lenses.
According to the given data, the power of the objective lens is 40X. Since, the power of the binocular lens is 15X, the following equation used is: Multiply 40 into 15 to get the value of 600X.
Magnification of an object is dependent on the following three factors:
- Thickness of the lens.
- Curvature of the lens.
- Speed of the light through the lens.
Different microscopes have different lenses with different magnifying powers, for different uses. Thus, an object magnifies 40X, each binocular lens magnifies 15X, and total magnification of the object being viewed is 600X.
Microbiology with Diseases by Taxonomy Chapter 4 Answers 1L
According to the fig in Labeling 1, the photographs labeled are shown with corresponding type of microscope, they are as follows:
- Scanning electron microscope.
- Bright field microscope.
- Phase contrast microscope:
- Fluorescent microscope:
- Transmission electron microscope:
- Nomarski microscope:
Microbiology with Diseases by Taxonomy Chapter 4 Answers 1MC
The smallest unit is the nanometer among the given options of decimeter, millimeter, micrometer, and nanometer.
Nanometer: A nanometer is one-thousandth of a micrometer. A nanometer can also be written as 1/100,000,000 or 10-9 m. It is the smallest unit of length used. The unit of nanometer is used to determine the length of microorganisms in Microbiology. The diameter of a polio virus is measured in nanometers.
Hence, the correct answer is option (c) nanometer.
Decimeter: A decimeter is one-tenth part of a meter. A decimeter can also be written as 1/10 or 10-1 m. It is not the smallest unit of length used. The smallest unit of length is the nanometer. The unit of decimeter is rarely used to determine the length of microorganisms in Microbiology.
Hence, the option (a) is incorrect.
Millimeter: A millimeter one-hundredth part of a meter. A millimeter can also be written as 1/100 or 10-2 m. It is not the smallest unit of length used. The smallest unit of length is the nanometer. The unit of millimeter is used to determine the length of microorganisms in Microbiology. The diameter of a bacterial colony is measured in millimeters.
Hence, the option (b) is incorrect.
Micrometer: A micrometer is one-thousandth of a millimeter. A micrometer can also be written as 1/100,000 or 10-6 m. It is not the smallest unit of length used. The smallest unit of length is the nanometer. The unit of micrometer is used to determine the length of cells in Microbiology. The diameter of a white blood cell is measured in micrometers.
Hence, the option (d) is incorrect.
Microbiology with Diseases by Taxonomy Chapter 4 Answers 1SA
The principle “electrons travel as waves” applies to electron microscopy.
Explanation
In light microscopes, only visible light can be used. Other frequencies of waves cannot be used. But in electron microscopes, electrons are used. These electrons travel as waves with wavelengths between 0.01 nm – 0.001 nm.
In addition, due to low wavelengths, the resolving power of electron microscopes is higher than that of light microscopes. When the resolving power of a microscope increases, the magnification power of the microscope also increases.
Furthermore, the electrons generated as a beam and the electrons behave in a similar way, as light waves. Since, the electron beams have lower wavelength than light waves, the images seen in the electron microscopes are more detailed than seen through light microscopes.
Microbiology with Diseases by Taxonomy Chapter 4 Answers 2CT
The definition of species as “successfully interbreeding organisms” is not satisfactory for most microorganisms.
Interbreeding applies to humans as well as to some organisms, but it does not apply to microorganisms like bacteria. In bacteria, interbreeding can occur between two different species. Interbreeding does not necessarily need to be within a particular species. It can be outside the species in the case of bacteria.
Bacteria interbreed with other species through the process of asexual reproduction. This crossing of two different species produces a new species in the progeny. Bacteria also have a special characteristic where they can adapt plasmids from the surrounding environment. This helps them gain new characteristics.
Since bacteria do not stick to the definition of “successfully interbreeding organisms,” the definition does not hold good for them.
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The process of heat fixation can be described in the following way:
- Small sample of the culture is taken and placed on a clean glass slide. If culture is in a broth, a small drop of the liquid is taken. If the culture is taken from a Petri plate, the culture is diluted in a drop of distilled water.
- A smear is then made by spreading the bacterial cells across the glass slide.
- The smear is air dried and then heat fixed.
- In heat fixation, the slide is passed through the flame of a Bunsen burner. The smear is not directly passed through the flame. Only the opposite side of the glass slide is slowly passed through the flame.
Moreover, this technique was developed by Koch to fix the microorganisms firmly on the slide. This is because it prevents the cells from washing off during various procedures of staining. Thus, fixation of culture developed by Koch in bacteria was done by heat fixation.
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A nanometer is 1000 times smaller than a micrometer.
1000 times smaller: A nanometer is 1000 times smaller than a micrometer. A nanometer is one-thousandth of a micrometer. A nanometer can also be written as 1/100,000,000 or 10-9 m. It is the smallest unit of length used.
Hence, the correct answer is option (d).
10 times larger: A nanometer is not 10 times larger than a micrometer. A nanometer is 1000 times smaller than a micrometer. A nanometer is one-thousandth of a micrometer. A nanometer can also be written as 1/100,000,000 or 10-9 m. It is the smallest unit of length used. A micrometer can also be written as 1/100,000 or 10-6 m.
Hence, the option (a) is incorrect.
10 times smaller: A nanometer is not 10 times smaller than a micrometer. It is 1000 times smaller than a micrometer. A nanometer is one-thousandth of a micrometer. A nanometer can also be written as 1/100,000,000 or 10-9 m. A micrometer can also be written as 1/100,000 or 10-6 m. It is the smallest unit of length used.
Hence, the option (b) is incorrect.
1000 times larger: A nanometer is not 1000 times larger than a micrometer. It is 1000 times smaller than a micrometer. A micrometer can also be written as 1/100,000 or 10-6 m. A nanometer is one-thousandth of a micrometer. A nanometer can also be written as 1/100,000,000 or 10-9 m. It is the smallest unit of length used.
Hence, the option (c) is incorrect.
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The definition of magnification given by a student is “magnification makes things bigger”.
Explanation
The process of magnification makes things looks bigger. But, the definition given by the student is false. This is because the process of magnification results, when light waves pass through the lens of the microscope. But, the things simply do not become bigger.
When light passes through a denser medium of glass, it refracts and bends. The refraction and bending of light rays, causes the magnification of the image. Thus, magnification of the image depends on the total magnifying power of the objective and the ocular lenses of the microscope.
The process of magnification depends on three factors:
- Thickness of lens.
- Curvature of lens.
- Speed of light through the lens.
Microbiology with Diseases by Taxonomy Chapter 4 Answers 3CT
Taxonomy is the system of classification of organisms into different groups.
An example would be:
In taxonomy, we see the classification of an organism into different groups. In the above example, we see that the panther has some common characteristics with many groups. So, the main objective of taxonomy is to group all individuals having common characteristics into one class.
When new organisms are discovered, its characteristics are studied to see if they match the characteristics of the existing classes. If the organism has unique characteristics, then it is kept under a separate group.
With the exception of the discovery of new organisms, the present system of taxonomy is likely to remain the same. The main reason for this is that no one has found ambiguities in the present system so far.
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Immersion oil is used with 100X lens. When immersion oil is placed between the immersion lens and the slide, the light passing through the lens travels through the slide. In addition, no light rays refract between the lens and the slide. This increases the numerical aperture.
Resolution is the ability to distinguish two objects close to each other, the better the resolution, and the better is the image. When the numerical aperture is increased, the resolution of the microscope is also increased.
Thus, all the light rays coming from the source of light pass through the specimen, which helps to see the image better. No light rays are refracted on the increase of resolution.
Immersion oil increases the numerical aperture, which increases resolution because more light rays are involved.
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Resolution is best described as the ability to distinguish between two adjacent objects.
The ability to distinguish between two adjacent objects: Resolution is the ability to distinguish two objects, which are next to each other. The better the resolution, the better two objects can be distinguished. Resolution is also called the resolving power of a microscope.
Hence, the correct option is (c) the ability to distinguish between two adjacent objects.
The ability to view something that is small: Resolution is not the ability to view something that is small. It is the ability to distinguish two objects which are next to each other. Resolution is also called the resolving power of a microscope. The better the resolution, the better two objects can be distinguished.
Hence, the option (a) is incorrect.
The ability to magnify a specimen: The ability to magnify a specimen is known as magnification. Magnification is indicated by a number which is followed by the letter X. Resolution is the ability to distinguish two objects which are next to each other.
Hence, the option (b) is incorrect.
The difference between two waves of electromagnetic radiation: The difference between two waves in electromagnetic radiation is called wavelength. Electromagnetic radiation includes X-rays, microwaves and radio waves. All these waves differ in their wavelength. Resolution is the ability to distinguish two objects, which are next to each other.
Hence, the option (d) is incorrect.
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Electron microscopes can magnify only on dead organisms.
Explanation
Specimens are prepared, for viewing through electron microscopes and need to go through many processes. Very thin specimens are used, because they do not contain air molecules that can absorb electrons.
In addition, if whole cells are examined, the specimen needs to be dehydrated and embedded in plastic. Moreover, the cells are cut in an ultra-microtome to a thickness of 100 nm. These thin slices are then inserted into the microscope.
Since, vacuuming and slicing of the specimen is required, for every cell and tissue, living organisms cannot be studied under electron microscopes. The different processes of dehydration and sectioning are done to distort the specimen to some extent.
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A microbiology student says that the magnification of the microscope can be increased by adding immersion oil. This statement is wrong.
The oil immersion technique is used to increase the resolution of a microscope. When viewing a specimen without immersion oil, the light rays pass from the air into the glass slide. This change in the medium causes refraction and bending of the light rays.
To prevent this refraction, immersion oil is added. The immersion oil has a refractive index which is identical to that of the glass slide. So, since both the glass slide and the oil have the same refractive index, no refraction or bending of the light rays are seen.
This gives a clearer image of the object. This is the main purpose of oil immersion technique.
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The principle of contrast is used in phase microscopes like phase contrast and differential interference contrast microscopes.
- In phase contrast microscopes, the background of the object is dark, while the object is brightly lit. Some cell structures like cilia and flagella cannot be seen well in bright field microscopes. But, they can be seen in phase contrast microscopes. Phase microscopes use the principle of in-phase and out-of-phase waves. When light waves are in-phase, the image appears bright. When light waves are out-of-phase, the background appears dark, since the light waves cancel each other.
- In differential interference contrast microscopes, follows the same principle of phases of light waves. In addition, these microscopes also possess prisms, which split the light into component colors. This drastically increases the contrast of the image. A three-dimensional appearance is also seen.
Thus, contrast refers to the difference in intensity between two objects.
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Curved glass lenses both refract and bend light.
Refract: Curved glass lenses refract light. But they can also bend light. When a lens is curved, the light rays passing through the periphery are refracted more than the light rays passing through the center. This makes the light rays focus on a focal point. So, curved lenses can also bend light.
Hence, the option (a) is correct.
Bend: Curved glass lenses can bend light. But they can also refract light. The light rays bend when they enter a denser medium when compared to air. When light rays enter a lens, they bend due to the optical density of the lens. When these light rays leave the lens, they bend again. So, curved lens can also refract light.
Hence, the option (b) is correct.
Magnify: Magnification of an object can result when light rays enter a lens. The degree of magnification depends on the thickness of the lens, the curvature of the lens and the speed with which light is transmitted through the lens. The curvature of the lens is not the only criteria for magnification of an object.
Hence, the option (c) is incorrect.
Both a and b: The options of (a) and (b) are bending and refracting of light. Curved glass lenses have the properties of both bending and refracting light rays.
Hence, the correct option is (d) both a and b.
Microbiology with Diseases by Taxonomy Chapter 4 Answers 4SA
The order of substances used in the Gram stain is, as follows:
- Primary stain
- Mordant
- Decolorizing agent
- Counter stain
The description of the process of Gram stain is, as follows:
- A smear is made with culture on a glass slide.
- The smear is air dried and heat fixed.
- The smear is then flooded with the primary stain.
- After some time, the stain is washed off and the smear flooded with the mordant.
- The mordant is used to bind the primary stain to the cells.
- The mordant is washed off and the decolorizer used.
- After the decolorizer is washed off, the counter stain is used.
- The counter stain is washed off and the cells viewed under the microscope.
- If the cells are Gram positive cells, they are violet in color while Gram negative cells are seen in red color.
Microbiology with Diseases by Taxonomy Chapter 4 Answers 5CT
The ocular lens of a light microscope has 10X magnifying power and 0.3 ?m resolution. When using the oil immersion lens, we cannot use the other ocular lenses of the microscope.
Since the resolution power of the microscope is 0.3 ?m, it indicates that when two objects are at a distance of 0.3 ?m, the microscope can detect them as two separate objects. By using the oil immersion lens, we are increasing the resolution of the microscope.
Since 400 nm and 40 nm are much greater distances than 0.3 ?m, we can resolve two objects at distances of 400 nm and 40 nm. By using the oil immersion lens, we can easily distinguish two objects at a distance of 400 nm and 40 nm.
Microbiology with Diseases by Taxonomy Chapter 4 Answers 5FB
The principle of staining in microbiology is to use stains, which bind ionically to the cells. Stains are usually either positively charged or negatively charged.
- Positively charged stains are called cationic chromophores.
- Negatively charged stains are called anionic chromophores.
In the cell, structures like DNA (deoxyribonucleic acid) and proteins have negative charge. DNA contains phosphate in its background, which gives a negative charge. Proteins have charged amino acids, but they also contain phosphate bonds. Hence, both DNA and proteins come under negatively charged molecules.
Moreover, on trying to stain negatively charged organelles cationic chromophores are used. Positively charged structures are stained with anionic chromophores.
Thus, cationic chromophores such as methylene blue ionically bond to negatively charged chemicals, such as DNA and proteins.
Microbiology with Diseases by Taxonomy Chapter 4 Answers 5MC
The factors which are important in making an image appear larger are the thickness, curvature of the lens, and the speed of light rays that passes through the lens.
The thickness of the lens: The thickness of the lens is an important factor in the magnification of an object. The thickness of the lens determines the speed of the light rays passing through the lens. But, the thickness of the lens is not the only factor responsible for the magnification of an object. The other factors are the curvature of the lens, and the speed of light rays that passes through the lens.
Hence, the option (a) is incorrect.
The curvature of the lens: The curvature of the lens is an important factor in the magnification of an object. The curvature of the lens refracts the light rays passing through the periphery of the lens. But, the curvature of the lens is not the only factor responsible for the magnification of an object. The other factors are the thickness of the lens, and the speed of light rays passing through the lens.
Hence, the option (b) is incorrect.
The speed of the light that passes through the lens: It is an important factor in the magnification of an object. But, the speed of the light that passes through the lens is not the only factor responsible for the magnification of an object. The other factors are the thickness of the lens and the curvature of the lens.
Hence, the option (c) is incorrect.
All of the above: All the above given options are correct. Each of the given options is important in the magnification of an image. In the absence of any one of the above factors, magnification of the object does not occur.
Hence, the correct option is (d) all of the above.
Microbiology with Diseases by Taxonomy Chapter 4 Answers 5SA
Latin is used in taxonomic nomenclature because of the following reasons:
- The rules of nomenclature make it mandatory that all taxa should have Latin names.
- The main language used by scientists during the time of Linnaeus was Latin.
- Using the language of Latin is done to avoid making the national language of any country as the language of taxonomy.
Even though the common names of the organisms may differ from area to area, the scientific name remains unchanged. This preference for the language of Latin was seen during the time of Linnaeus.
Linnaeus suggested the binomial nomenclature in which every organism has two names – one is the genus name and the other is the species name. The scientific names can be given on the basis of different aspects.
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Resolution: The resolution in light microscopes is 200 nm to 10 mm. The resolution in transmission electron microscopes is 0.078 nm to 100 ?m.
Hence, the option (b) is incorrect.
Wavelengths: The light microscope uses light rays while electron microscopes use electrons. In light microscopes, the light rays pass through the specimen and in electron microscopes, a beam of electrons pass through the specimen.
Hence, the option (c) is incorrect.
All of the above: The differences between light microscopes and transmission electron microscopes are magnification, resolution, and wavelengths. Since, all these factors are covered in the above options, all of these options are correct.
Hence, the correct option is (d) all of the above.
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The three characteristics of a specific epithet are given below:
- The specific epithet is always written in lowercase letters.
- The name is usually an adjective.
- It is always written in italics.
The specific epithet is always written in lowercase letters according to the rules given by Linnaeus. Linnaeus also suggested that the species name should always be in italics along with the genus name.
The species name is usually an adjective, and can specify the nature of the organism, or can honor a particular scientist. A genus name can be common for few species, but a species name is always specific and unique for a specific organism.
When manually writing the genus and species names, they should be underlined.
Microbiology with Diseases by Taxonomy Chapter 4 Answers 7MC
Simple microscope: A simple microscope does not produce a three-dimensional image. A three-dimensional image with a shadowed image is seen in a differential interference contrast microscope. These microscopes use prisms to split the light rays into different colors. Prisms are not used in simple microscopes.
Hence, the option (a) is incorrect.
Fluorescent microscope: A fluorescent microscope does not produce a three-dimensional image. A three-dimensional image with a shadowed image is seen in a differential interference contrast microscope. These microscopes use prisms to split the light rays into different colors. Prisms are not used in fluorescent microscopes.
Hence, the option (c) is incorrect.
Transmission electron microscope: A transmission electron microscope does not produce a three-dimensional image. A three-dimensional image with a shadowed image is seen in a differential interference contrast microscope. These microscopes use prisms to split the light rays into different colors. Prisms are not used in transmission electron microscopes. Electron microscopes use electron beams.
Hence, the option (d) is incorrect.
Microbiology with Diseases by Taxonomy Chapter 4 Answers 7SA
The study of the nucleotide sequences of ribosomal RNA (ribonucleic acid) fits into a discussion of taxonomy.
The scientist Woese studied the sequences of the ribosomal RNA in different organisms. These sequences are usually present in all cells, and are vital for protein synthesis. This scientist found differences in the sequences of ribosomal RNA.
Based on these differences, Woese classified organisms into three groups:
- Eukarya
- Bacteria
- Archaea
The domain Eukarya contains eukaryotic ribosomal RNA sequences. The domains Bacteria and Archaea include all the prokaryotic cells. The ribosomal RNA sequences of these two domains differ from each other, and from eukaryotic rRNA sequences.
Hence, the rRNA sequences serve as a basis for the classification of cells into three domains.
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Phase-contrast microscope: These microscopes do not combine the greatest magnification with the best resolution. This is seen only in confocal microscopes. The usage of fluorescent dyes and combination of individual images is seen in confocal microscopes.
Hence, the option (b) is incorrect.
Dark-field microscope: These microscopes do not combine the greatest magnification with the best resolution. This is seen only in confocal microscopes. The usage of fluorescent dyes and combination of individual images is seen in confocal microscopes. In the dark-field microscope, a condenser is used, which is responsible for the contrast.
Hence, the option (c) is incorrect.
Bright-field microscope: The resolution and magnification in bright-field microscopes are not the highest. The usage of fluorescent dyes and combination of individual images is seen in confocal microscopes. The greatest magnification with the best resolution is seen only in confocal microscopes.
Hence, the option (d) is incorrect.
Microbiology with Diseases by Taxonomy Chapter 4 Answers 8SA
A living cell can be magnified with an atomic force microscope, but cannot be viewed by electron microscopes or scanning tunneling microscopes.
In an atomic force microscope, a pointed probe is used to lightly touch the surface of the specimen. A laser beam is aimed at the tip of the probe. When this beam is deflected by the structure of the specimen, it is shown on a computer. The specimen does not need to be electrically conductive to be viewed by the atomic force microscope.
In electron microscopes, the processing of the specimen needs to be done. Since electrons are used, the instrument is under vacuum. The specimens must be dehydrated and sectioned for use. No air molecules should be present, which can deflect the electrons.
In scanning tunneling microscopes, a probe is used, which is kept at a distance from the specimen. The flow of electrons from the probe to the surface of the specimen is measured. Since electrons are used, the specimen needs to be processed specially.
Hence, due to the above reasons, live specimens cannot be viewed under electron microscopes or scanning tunneling microscopes.
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Negative stains such as eosin are also called capsule stains.
Capsule stains: Capsular stains are negative stains. They do not stain the microbe, but stain the surrounding medium. Eosin and nigrosin are used as negative stains. These are acidic stains, which are repelled by the charge on the cells and do not stain them.
Hence, the correct option is (a) capsule stains.
Endospore stains: Negative stains like eosin are not used in endospore staining. Negative stains do not stain the microbe, but stain the surrounding medium. They are acidic stains, which are repelled by the charge on the cells and do not stain them. Negative stains are used as capsular stains.
Hence, the option (b) is incorrect.
Simple stains: Negative stains like eosin are not used in simple staining. Negative stains do not stain the microbe, but stain the surrounding medium. In simple staining, the microbe is stained with only one stain. Negative stains are used as capsular stains.
Hence, the option (c) is incorrect.
Acid-fast stains: Negative stains like eosin are not used in acid-fast staining. Negative stains do not stain the microbe, but stain the surrounding medium. In acid-fast staining, an acid is used to make sure that the stain penetrates the cell. Negative stains are used as capsular stains.
Hence, the option (d) is incorrect.
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Domain: The domain to which the organism belongs is not written in lowercase letters. The first letter of the domain is capitalized and the rest of the letters are written in lowercase. An example is Bacteria. The specific epithet is always written in lowercase letters.
Hence, the option (b) is incorrect.
Genus: The genus to which the organism belongs is not written in lowercase letters. The first letter of the genus is capitalized, and the rest of the letters are written in lowercase. An example is Plasmodium. The specific epithet is always written in lowercase letters. Hence, the option (c) is incorrect.