MicroBiology MCQs with Answer and Explnation | Chapter 60

Answer: Lord Lister

Lord Lister, a British surgeon, is credited with pioneering antiseptic methods in the 1860s. He used carbolic acid (phenol) to sterilize surgical instruments and the operating environment, significantly reducing post-operative infections.

The other options are incorrect:

• Iwanowski: While important in the field of microbiology, Dmitri Iwanowski discovered viruses, not antiseptic methods.
• Beijerinck: Martinus Beijerinck, another microbiologist, focused on isolating specific bacteria, not developing antiseptic techniques.
• Edward Jenner: Edward Jenner is known for developing the smallpox vaccine, a preventative measure against a specific disease, not antiseptics for general wound care.

Answer: Pili

During conjugation, bacteria establish a direct cell-to-cell connection through a pilus (plural: pili). This pilus acts like a bridge, allowing the transfer of genetic material, typically a plasmid DNA copy, from the donor bacterium to the recipient bacterium.

The other options are incorrect:

• Cell wall: The cell wall provides structural support and protection for the bacteria but doesn’t have a role in transferring genetic material during conjugation.
• Medium: The surrounding medium (liquid or solid) where bacteria grow doesn’t facilitate the specific transfer of genetic material between bacteria during conjugation.
• Capsule: The capsule is a sugary layer surrounding some bacteria, offering additional protection but not involved in conjugation or genetic exchange.

Answer: Chondroids

Meosomes, although previously thought to be functional structures, are actually artifacts created during the process of preparing bacterial cells for electron microscopy using chemical fixation. The term “chondroids” is another name for mesosomes.

The other options are incorrect:

• Mitochondria: Mitochondria are complex membrane-bound organelles found in eukaryotic cells, responsible for cellular respiration. Bacteria lack these structures and rely on mesosomes (or rather, the enzymes dispersed throughout the plasma membrane) for some respiratory functions.
• Endoplasmic reticulum: The endoplasmic reticulum is another membrane-bound organelle in eukaryotes involved in protein synthesis, transport, and modification. Bacteria lack this organelle as well.
• Plasmids: Plasmids are small, circular pieces of DNA separate from the bacterial chromosome. They can carry additional genes and can be transferred between bacteria during conjugation, but they are not structural components of the cell membrane like mesosomes.

Answer: MLD

MLD stands for Minimum Lethal Dose. It refers to the smallest number of bacteria or virus particles needed to cause death in 50% of a test animal population under controlled conditions. This value helps assess the virulence (disease-causing ability) of a pathogen.

The other options are incorrect:

• LD50: LD50 refers to the Lethal Dose 50, which is the amount of a substance (including toxins or some bacterial strains) needed to kill 50% of a test animal population. It’s a broader term applicable to various toxins and pathogens, not specific to bacteria causing death through infection.
• ID: ID refers to Infectious Dose, which is the minimum amount of a pathogen needed to cause an infection in 50% of a test animal population. While related, ID doesn’t necessarily lead to death, unlike MLD.

Answer: Pneumococci

Frederick Griffith, in 1928, conducted his landmark experiment demonstrating bacterial transformation using Streptococcus pneumoniae, commonly referred to as pneumococci. This experiment provided the first evidence of bacteria acquiring genetic material from other bacteria.

The other options are incorrect:

• H. influenzae: Haemophilus influenzae, though a bacterium, wasn’t used by Griffith in his transformation experiment.
• Bacillus species: There are various Bacillus species, some pathogenic, but Griffith didn’t use them for his transformation discovery.
• E. coli: Escherichia coli, a common lab bacterium, wasn’t the focus of Griffith’s transformation experiment in 1928.

Answer: Virulence

Virulence refers to the degree of pathogenicity, which is the ability of a microorganism to cause disease in a host. A highly virulent strain can cause severe illness, while a less virulent strain may cause mild or no symptoms at all.

The other options are incorrect:

• Pathogen: A pathogen is any microorganism or infectious agent that can cause disease. Not all pathogens are equally virulent, meaning they don’t all cause the same severity of illness.
• Infection: Infection is the invasion and multiplication of a pathogen in a host’s tissues. While infection is a necessary step for disease to occur, virulence determines the severity of the disease.

Answer: Conjunction

Joshua Lederberg and Esther Tatum, in 1946, conducted experiments that revealed bacterial conjugation. Their work demonstrated that bacteria could transfer genetic material through direct cell-to-cell contact via a pilus, allowing for the exchange of genes like antibiotic resistance.

The other options are incorrect:

• Transformation: Transformation, although another method of horizontal gene transfer in bacteria, involves the uptake of free DNA from the surrounding environment, not direct cell contact.
• Mutation: Mutation refers to a change in the genetic material of an organism, which can occur spontaneously or due to environmental factors. While mutations can contribute to virulence or antibiotic resistance, Lederberg and Tatum’s work focused on the transfer of existing genetic material, not mutations themselves.
• Plasmids: Plasmids are the small, circular DNA molecules that can be transferred during conjugation, but they were not the specific phenomenon Lederberg and Tatum described. Their work focused on the process of transfer, not the specific DNA molecule involved.

Answer: Leeuwenhock

Antonie van Leeuwenhoek, a pioneer in microbiology, is credited with developing the hanging drop method for motility studies in the late 17th century. He used this technique to observe the movement of microorganisms through his early microscopes.

The other options are incorrect:

• Robert Koch: While Robert Koch made significant contributions to microbiology in the 19th century, including developing postulates for identifying infectious agents, he is not credited with inventing the hanging drop method.
• Louis Pasteur: Louis Pasteur, another prominent microbiologist of the 19th century, focused on germ theory and fermentation processes. He did not develop the hanging drop method.
• Jenner: Edward Jenner is best known for developing the smallpox vaccine, a major advancement in preventing infectious disease. He is not associated with the hanging drop technique for motility studies.

Answer: Both Milk and Fruit juices

Louis Pasteur conducted fermentation experiments using a variety of substrates, including.

• Milk: Pasteur’s work on milk fermentation helped develop the process of pasteurization, which destroys harmful bacteria and extends the shelf life of milk.
• Fruit Juices: Pasteur also studied the fermentation of fruit juices, which contributes to the production of alcoholic beverages like wine and cider.

The other options are incorrect:

• Food material: This is too broad a term. While Pasteur did use various food materials in his fermentation experiments, specifying milk and fruit juices provides more accurate detail.

Answer:

Paul Ehrlich, a German physician and scientist, proposed modern concepts of chemotherapy. He introduced the concept of “magic bullets,” which are chemicals that selectively target and destroy pathogens without harming the host. Ehrlich’s work laid the foundation for the development of chemotherapy as a treatment for infectious diseases and cancer.

The other options are incorrect:

• Joseph Lister: Joseph Lister, a British surgeon, is known for his pioneering work in antiseptic surgery, not chemotherapy.
• Elie Metchnikoff: Elie Metchnikoff, a Russian immunologist, is renowned for his research on the immune system and phagocytosis, but he did not propose modern concepts of chemotherapy.

Answer: Klein Berger

L-forms, also known as L-phase bacteria, were discovered by Klein Berger. L-forms are a variant of bacteria that lack a cell wall and can therefore adopt different shapes and sizes. They are of interest in microbiology due to their unique properties and implications for antibiotic resistance.

The other options are incorrect:

• Louis Pasteur: Louis Pasteur was a renowned French microbiologist who made significant contributions to the fields of microbiology and immunology, but he did not discover L-forms.
• Robert Koch: Robert Koch, a German physician and microbiologist, is known for his work in bacteriology, including his contributions to Koch’s postulates, but he did not discover L-forms.
• Antony von Leeuwenhock: Although Antonie van Leeuwenhoek was a pioneer in microscopy and made significant contributions to the field of microbiology, he did not discover L-forms.

Answer: Both Howard Ricketts and da Rocha-lima

The causative organism of Rocky Mountain spotted fever was first described independently by Howard Ricketts, an American pathologist, and da Rocha-lima, a Brazilian bacteriologist. Ricketts isolated the organism in 1906, while da Rocha-lima isolated and described it in 1910.

The other options are incorrect:

• Robert Koch: Robert Koch, a German physician and microbiologist, made significant contributions to the field of bacteriology, including Koch’s postulates, but he did not describe the causative organism of Rocky Mountain spotted fever.

Answer: De’Herelle

Félix d’Hérelle, a French-Canadian microbiologist, coined the term “bacteriophage” in 1917. He described these agents that lysed (destroyed) bacteria and believed they could be used as therapeutic agents.

The other options are incorrect:

• F.W. Twort: Frederick W. Twort independently discovered bacteriophages around the same time as d’Hérelle (1915), but it was d’Hérelle who named them.
• Beijerinck: Martinus Beijerinck, another microbiologist, is known for his work on isolating specific bacteria, not for naming bacteriophages.
• Jwanosky: Dmitri Iwanowski discovered viruses that infect plants, but the term “bacteriophage” specifically refers to viruses that infect bacteria.

Answer: F.W. Twort

Frederick William Twort, an English bacteriologist, discovered viral infection of bacteria independently in 1915. He observed the phenomenon of bacterial lysis caused by what he called “filterable agents,” which were later identified as bacteriophages.

The other options are incorrect:

• De’Herelle: Félix d’Herelle, a French-Canadian microbiologist, contributed significantly to the study of bacteriophages, coining the term “bacteriophage” and demonstrating their ability to lyse bacteria. However, he did not discover viral infection of bacteria.
• Beijerinck: Martinus Beijerinck, a Dutch microbiologist, made significant contributions to virology and microbiology, including the discovery of viruses, but he did not discover viral infection of bacteria.
• Jwanoksy: There is no known scientist named Jwanoksy in the context of the discovery of viral infection of bacteria. This option is incorrect.

Answer: Frank

Albert Bernhard Frank, a German botanist, is credited with first observing and describing mycorrhizae in 1885. He also coined the term “mycorrhiza” meaning “fungus root” to refer to the symbiotic association between fungi and plant roots.

The other options are incorrect:

• Funk: Casimir Funk is known for proposing the concept of vitamins, not for discovering mycorrhizae.
• Fisher: While there may have been other researchers like Alfred Fischer who studied plant-fungus relationships, Frank’s work is generally recognized as the foundational discovery of mycorrhizae.
• Crick: Francis Crick, along with James Watson, is famous for co-discovering the structure of DNA. They are not associated with mycorrhizae.

Answer: Attenuation

Attenuation refers to the process of reducing the virulence or pathogenicity of a microorganism. This can be achieved through various methods such as serial passage in laboratory conditions, genetic manipulation, or selection of naturally occurring less virulent strains. Attenuated strains of pathogens are often used in vaccine development to stimulate an immune response without causing disease.

The other options are incorrect:

• Exaltation: Exaltation refers to the opposite process of increasing the virulence or strength of a microorganism, which is not the correct term for the reduction of virulence.
• Both a and b: This option is incorrect because only “attenuation” is the correct term for the reduction of virulence. “Exaltation” is not related to this concept.

Answer: Exaltation

Exaltation refers to the opposite of attenuation. It describes an increase in virulence (disease-causing ability) of a microorganism. This can happen through various mechanisms, such as mutations that enhance toxin production or improve the ability to evade the host’s immune system.

The other options are incorrect:

• Attenuation: As mentioned previously, attenuation refers to a decrease in virulence.
• Both Exaltation and Attenuation: These terms represent opposite effects on virulence.

Answer: All of the above

Virulence, the degree of pathogenicity, can be measured using various methods, each providing a different perspective:

• LD (Lethal Dose): This refers to the amount of a substance (including toxins or some bacterial strains) needed to kill 50% of a test animal population. While not specific to bacteria causing death through infection, a high LD for a pathogen indicates its potential lethality.
• MLD (Minimum Lethal Dose): This specifically refers to the smallest number of bacteria or virus particles needed to cause death in 50% of a test animal population under controlled conditions. MLD directly assesses the lethality of a bacterial strain in causing death.
• ID (Infectious Dose): This refers to the minimum amount of a pathogen needed to cause an infection in 50% of a test animal population. Even if an infection doesn’t always lead to death, ID helps assess the ease with which a pathogen can establish itself in a host.

Answer: All of the above

Virulence is a complex trait influenced by various factors, and all the options you mentioned play crucial roles:

• Adhesions: These are surface molecules on pathogens that allow them to attach to host cells, a critical first step for establishing infection.
• Invasiveness: Some pathogens have mechanisms to invade and penetrate host cells or tissues, enabling them to spread and cause damage.
• Enzymes: Pathogens produce various enzymes that can break down host tissues, evade defense mechanisms, and acquire nutrients, all contributing to their virulence.

Answer:

Invasiveness refers to a pathogen’s ability to spread and penetrate host tissues after establishing an initial infection. This allows the pathogen to reach deeper tissues, damage them, and potentially establish itself in new locations within the host, worsening the infection.

The other options are incorrect:

• Adhesion: Adhesion is the initial attachment of a pathogen to host cells, a crucial first step for infection, but it doesn’t necessarily involve spreading within tissues.
• Toxigenicity: Toxigenicity refers to a pathogen’s ability to produce toxins, harmful substances that can damage host tissues and contribute to disease symptoms. While toxins can worsen the infection, they are not directly related to the ability to spread through tissues.

Answer: Hyaluronidase

Hyaluronidase is an enzyme produced by some bacteria and other pathogens that acts as a spreading factor. It breaks down hyaluronic acid, a major component of the connective tissues between cells in the host organism. This breakdown weakens the tissue barriers, allowing the pathogen to spread more easily and invade deeper tissues.

The other options are incorrect:

• Coagulase: Coagulase is an enzyme produced by some bacteria that can cause blood to clot. While it can contribute to infection by impeding the host’s immune response, it doesn’t directly spread the pathogen within tissues.
• Catalase: Catalase is an enzyme found in many organisms, including some bacteria. It helps break down hydrogen peroxide, a harmful byproduct of cellular processes. It doesn’t play a role in spreading pathogens.
• DNase: Deoxyribonuclease (DNase) is an enzyme that can break down DNA. While some pathogens might produce DNase, its primary function wouldn’t be to spread the pathogen itself but potentially to damage host cells or manipulate the immune response. It’s not a major spreading factor.

Answer: Escherich

Theodor Escherich, a German-Austrian pediatrician, first isolated and described Escherichia coli in 1885. He named the bacterium Bacterium coli commune, and it was later renamed Escherichia coli.

The other options are incorrect:

• Louis Pasteur: Louis Pasteur, a renowned microbiologist of the 19th century, focused on germ theory and fermentation processes. He is not credited with isolating E. coli.
• Shiga: Shigasaki Iga, also known as Shiga, is a Japanese bacteriologist who discovered a specific strain of E. coli (Shiga toxin-producing E. coli) responsible for severe dysentery. However, he wasn’t the first to isolate E. coli in general.
• Robert Koch: Similar to Pasteur, Robert Koch, another prominent microbiologist, is known for his work on identifying infectious agents, but not for isolating E. coli.

Answer: Robert Koch

Robert Koch, a German physician and microbiologist, is credited with discovering Mycobacterium tuberculosis, the bacterium that causes tuberculosis (TB), in 1882. His work fulfilled his postulates for identifying infectious agents, solidifying the link between this bacterium and the disease.

The other options are incorrect:

• Edward Jenner: Edward Jenner is known for developing the smallpox vaccine, a pioneering achievement in preventing infectious diseases. However, he was not involved in discovering the cause of tuberculosis.
• Louis Pasteur: Louis Pasteur, another prominent microbiologist of the 19th century, focused on germ theory and fermentation processes. He did not discover Mycobacterium tuberculosis.

Answer: Hansen

Gerhard Armauer Hansen, a Norwegian physician, discovered Mycobacterium leprae, the bacterium that causes leprosy, in 1873. His work is a significant milestone as it represented one of the first identifications of a bacterium as the cause of a specific human disease.

The other options are incorrect:

• Robert Koch: While Robert Koch made significant contributions to microbiology, including his postulates for identifying infectious agents, he did not discover Mycobacterium leprae.
• Edward Jenner: Edward Jenner is known for developing the smallpox vaccine, a preventative measure against a specific disease, not for discovering the bacterium causing leprosy.
• Louis Pasteur: Louis Pasteur, similar to Jenner, focused on germ theory and fermentation processes. He wasn’t involved in discovering the causative agent of leprosy.

Answer: Louis Pasteur

Louis Pasteur, a French chemist and microbiologist, is credited with isolating Streptococcus pneumoniae in 1881 alongside George Sternberg (US Army physician) While Sternberg also made the discovery independently, Pasteur’s work gained wider recognition. Streptococcus pneumoniae is the bacterium responsible for pneumonia and other infections.

The other options are incorrect:

• Robert Koch: Robert Koch, a prominent microbiologist, is not credited with isolating Streptococcus pneumoniae.
• Edward Jenner: Edward Jenner is known for developing the smallpox vaccine, not isolating bacteria causing pneumonia.
• Antony van Leewenhoek: While Antony van Leeuwenhoek was a pioneer in microbiology with his early microscopes, he predates the isolation of specific bacteria like Streptococcus pneumoniae in the 19th century.

Answer: Robert Koch

Robert Koch isolated Bacillus anthracis, the bacterium causing anthrax, in 1876. His work is significant because he not only isolated the bacterium but also fulfilled his postulates, solidifying the link between B. anthracis and anthrax.

The other options are incorrect:

• Louis Pasteur: While Louis Pasteur made significant contributions to microbiology, he is not credited with isolating Bacillus anthracis.
• Antony van Leeuwenhoek: Similar to the previous question, Antony van Leeuwenhoek, a pioneer in microbiology with early microscopes, predates the specific isolation of B. anthracis in the 19th century.

Answer: Louis Pasteur

Streptococcus pneumoniae, the bacterium responsible for causing pneumonia and other respiratory infections, was isolated by the French microbiologist Louis Pasteur in 1881. Pasteur’s work on identifying the bacterium contributed to our understanding of its role in causing disease.

The other options are incorrect:

• Robert Koch: While Robert Koch made significant contributions to microbiology and bacteriology, he was not the one who isolated Streptococcus pneumoniae.
• Edward Jenner: Edward Jenner was an English physician known for developing the smallpox vaccine, but he was not involved in the isolation of Streptococcus pneumoniae.
• Antony von Leewenhock: Although Antonie van Leeuwenhoek was a pioneer in microscopy and made important contributions to microbiology, he did not isolate Streptococcus pneumoniae.

Answer: Schroeter and Gessard

The bacterium Pseudomonas aeruginosa was first named by Johann Friedrich Julius Schroeter and Marie David Alfred Gessard in 1882. They classified it as Pseudomonas pyocyanea based on its blue pigment production (pyocyanin). The name was later changed to Pseudomonas aeruginosa.

The other options are incorrect:

• Robert Koch: Robert Koch, a prominent microbiologist, is not credited with the initial naming of Pseudomonas aeruginosa.
• Louis Pasteur: Similar to Koch, Louis Pasteur is not associated with naming this specific bacterium.
• Edward Jenner: Edward Jenner is known for developing the smallpox vaccine, not for naming bacteria.

Answer: Schaudinn and Hoffman

Fritz Schaudinn and Erich Hoffmann, German scientists, are credited with discovering Treponema pallidum, the bacterium that causes syphilis, in 1905. They observed the spirochete-shaped bacteria in syphilitic lesions using dark-field microscopy, a technique crucial for visualizing this non-staining bacterium.

The other options are incorrect:

• Robert Koch: Robert Koch, a prominent microbiologist, is not credited with discovering Treponema pallidum.
• Louis Pasteur: Similar to Koch, Louis Pasteur is not associated with discovering the syphilis-causing bacterium.
• Edward Jenner: Edward Jenner is known for developing the smallpox vaccine, not for discovering bacteria related to syphilis.

Answer: Neisser in 1879

Albert Ludwig Sigesmund Neisser, a German physician, is credited with first describing Neisseria gonorrhoeae, the bacterium that causes gonorrhea, in 1879.

The other options are incorrect:

• Pasteur in 1878: Though Louis Pasteur made significant contributions to microbiology in the 19th century, he is not associated with the discovery of Neisseria gonorrhoeae. The year mentioned (1878) is also slightly off.
• Robert Koch: Similar to Pasteur, Robert Koch, another prominent microbiologist, is not credited with discovering the causative agent of gonorrhea.

Answer: Schaudinn and Hoffman

Fritz Schaudinn and Erich Hoffmann, German scientists, are credited with discovering Treponema pallidum, the bacterium that causes syphilis, in 1905. They observed the spirochete-shaped bacteria in syphilitic lesions using dark-field microscopy, a technique crucial for visualizing this non-staining bacterium.

The other options are incorrect:

• Louis Pasteur: Louis Pasteur, a renowned microbiologist, focused on germ theory and fermentation processes. He wasn’t involved in isolating Treponema pallidum.
• Burgey: The name “Burgey” is not associated with the discovery of Treponema pallidum. There might be a misspelling of another scientist’s name, but based on the provided options, it’s unlikely to be relevant.
• Laennec: René Laennec, a French physician, is known for inventing the stethoscope in the early 19th century. He wasn’t involved in microbiology or the discovery of Treponema pallidum.

Answer: Haemophilus influenza

Haemophilus influenzae is a bacterium that can cause respiratory tract infections, including those that present with symptoms similar to the common cold. It is a common cause of acute otitis media (ear infection), sinusitis, and upper respiratory tract infections, especially in children.

The other options are incorrect:

• Pseudomonas: Pseudomonas aeruginosa is a bacterium known for causing opportunistic infections, particularly in immunocompromised individuals, but it is not typically associated with cold-like symptoms.
• E. coli: Escherichia coli is a bacterium commonly found in the gastrointestinal tract of humans and animals. While some strains of E. coli can cause respiratory infections, they are not typically associated with cold-like symptoms.
• Haemophilus streptococcus: There is no bacterium called “Haemophilus streptococcus.” It seems to be a combination of two different bacterial genera, Haemophilus and Streptococcus. Streptococcus species can cause various infections, but they are not typically associated with cold-like symptoms.

Answer: Log

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Answer: Log

Bacterial cells are at their metabolic peak during the logarithmic (log) phase of growth, also known as the exponential phase. In this phase, bacterial cells multiply rapidly, and metabolic activity is at its highest as they utilize available nutrients for growth and reproduction.

The other options are incorrect:

• Lag phase: The lag phase occurs immediately after inoculation into a new environment, during which bacteria adapt to their surroundings and prepare for growth. Metabolic activity is low during this phase.
• Stationary phase: In the stationary phase, bacterial growth slows down as the rate of cell division equals the rate of cell death. Metabolic activity decreases as resources become limited.
• Decline phase: Also known as the death phase, the decline phase occurs when the number of dying cells exceeds the number of new cells being produced. Metabolic activity decreases sharply as cells die off.

Answer: Lippolysacharide

Endotoxin, a toxic component of the outer membrane of gram-negative bacteria, is primarily composed of lipopolysaccharide (LPS). LPS plays a crucial role in the structural integrity of the outer membrane and interacts with the host immune system, potentially triggering inflammatory responses.

The other options are incorrect:

• Peptidoglycan: Peptidoglycan is a rigid layer found in the cell wall of both gram-positive and gram-negative bacteria. It provides structural support and shape to the cell, but it’s not the endotoxin.
• Teichoic acid: Teichoic acid is a polymer found in the cell wall of gram-positive bacteria, not gram-negative bacteria. It has functions similar to peptidoglycan but is not an endotoxin.
• Inner membrane: The inner membrane is a phospholipid bilayer found inside the cell wall in both gram-positive and gram-negative bacteria. It’s not the location of endotoxin.

Answer: Binary fission

Mycoplasma, the smallest known free-living organisms, reproduce primarily through binary fission, similar to many bacteria. In binary fission, the parent cell replicates its DNA, divides its cytoplasm and organelles, and then splits into two roughly equal daughter cells.

The other options are incorrect:

• Budding: Budding is a mode of reproduction where a smaller daughter cell grows and pinches off from a larger parent cell. While some bacteria can reproduce by budding, it’s not the primary mode for Mycoplasma.
• Bursting: Bursting is not a typical mode of reproduction in Mycoplasma or most bacteria. Cell lysis (bursting) can occur due to various factors but wouldn’t be considered a controlled reproductive process.
• Binary fusion: Binary fusion, where two cells fuse to form a single cell, is not a known reproductive strategy in Mycoplasma.

Answer: Icosahedral, with envelope, ds DNA

Herpes viruses are characterized by having an icosahedral capsid, an envelope derived from the host cell membrane, and a double-stranded DNA (dsDNA) genome. This combination of features is typical of the structure of herpes viruses.

Incorrect Options:

1. Polyhedral with envelope, ds DNA: While some viruses have polyhedral capsids, this description does not match the typical structure of herpes viruses, which have an icosahedral capsid.
2. RNA, helical with envelope: This description matches the structure of certain RNA viruses, particularly those with helical capsids, such as the influenza virus or the measles virus. Herpes viruses, however, have a dsDNA genome, not an RNA genome.
3. ds DNA, brick shape: This description does not match the typical structure of herpes viruses. The term “brick shape” is not typically used to describe the morphology of viruses, and herpes viruses have an icosahedral capsid, not a brick shape.

Answer: Mycoplasms

Mycoplasmas are bacteria that lack a cell wall and typically produce colonies with a characteristic “fried egg” appearance on solid media. This appearance is due to their lack of cell wall, which leads to the colonies having a dense center (the “yolk”) surrounded by a translucent outer zone (the “white”).

The other options are incorrect:

• Mycobacteria: Mycobacteria are acid-fast bacteria with a distinct cell wall structure that does not produce colonies with a fried egg appearance. Instead, mycobacterial colonies often appear rough or wrinkled on solid media.
• Mycoplasts: “Mycoplasts” is not a recognized term in microbiology. It appears to be a misspelling or a confusion with other terms such as mycoplasmas or mycoplasmids.
• Bacteroides: Bacteroides are anaerobic bacteria commonly found in the human gastrointestinal tract. They do not typically produce colonies with a fried egg appearance on solid media.

Answer: Halophile

Halophiles are organisms that thrive in environments with high salt concentrations, typically requiring sodium chloride for growth and survival. Their cell membranes are adapted to function in these salty conditions.

The other options are incorrect:

• Basophile: These are cells with a high concentration of basophilic substances, which stain dark blue with certain dyes. They have nothing to do with salt requirements.
• Barophile: These organisms thrive under high pressure environments, like deep sea. Sodium chloride is not a specific requirement for them.
• Xerophile: These organisms prefer dry environments and have adaptations to conserve water. They don’t necessarily require high salt concentrations.

Answer: Lactic acid + alchohol + CO2

Heterolactic acid bacteria are a type of lactic acid bacteria that produce lactic acid along with other metabolic byproducts such as alcohol (usually ethanol) and carbon dioxide (CO2). This type of fermentation pathway is characteristic of heterolactic fermentation.

The other options are incorrect:

• Lactic acid only: This describes homolactic acid bacteria, which solely produce lactic acid from sugars.
• Lactic acid + H2O + CO2: While CO2 is produced, water (H2O) is not a specific product of heterolactic fermentation.
• Lactic acid + CO2: This outcome is possible, but it excludes the production of alcohol, which is a key characteristic of heterolactic fermentation.

Answer: Glucose fermentation Vs Respiration

One way to distinguish Pseudomonas species from E. coli is by their metabolic characteristics related to glucose fermentation and respiration. Pseudomonas species are typically aerobic and utilize oxidative metabolism, while E. coli is facultatively anaerobic and can ferment glucose in the absence of oxygen. Therefore, Pseudomonas species will predominantly utilize respiration for energy production, while E. coli can ferment glucose to produce energy when oxygen is unavailable.

The other options are incorrect:

• Gram staining: Both Pseudomonas species and E. coli are Gram-negative bacteria, so Gram staining would not reliably distinguish between them based on this criterion alone.
• Morphology: While there may be subtle morphological differences between Pseudomonas species and E. coli, these differences may not be distinctive enough to reliably differentiate between them.
• All of the above: While Gram staining and morphology can provide some information about bacterial identity, they may not be sufficient to distinguish between Pseudomonas species and E. coli. Glucose fermentation versus respiration is a more reliable criterion for differentiation.

Answer: Both Cephaleuros and Prototheca

• Spirogyra: This is a green alga and not known to be pathogenic to humans.
• Cephaleuros: This is a parasitic fungus that can cause a scalp infection called black piedra in humans.
• Prototheca: These are single-celled algae that can cause opportunistic infections in immunocompromised individuals.

The other options are incorrect:

• Spirogyra: As mentioned earlier, it’s not pathogenic to humans.

Answer: Bacteriophages

Bacteriophages, also known as phages, are viruses that specifically infect and replicate within bacterial cells. They are considered bacterial parasites because they rely on the cellular machinery of bacteria to replicate and produce new viral progeny. Bacteriophages have evolved various mechanisms to infect bacteria and can be lytic (resulting in bacterial cell lysis) or lysogenic (integrating their genome into the bacterial chromosome).

The other options are incorrect:

• Fungi: Fungi are eukaryotic organisms and cannot be parasites of bacteria, which are prokaryotic.
• Commensal: Commensalism is a relationship where two organisms live together, but one benefits while the other is neither harmed nor helped. Parasites, on the other hand, harm their host.

Answer:

Anthrax spores can linger in the soil for decades. Herbivores grazing on contaminated land are most susceptible to infection by ingesting the spores.

• Cattle: These are commonly affected by anthrax, especially in areas with a history of the disease.
• Sheep: Similar to cattle, sheep grazing on contaminated pastures can become infected with anthrax.

The other options are incorrect:

• Rats: While theoretically possible, rats are less likely to be infected with anthrax compared to grazing animals. Their diet is more varied and they might not encounter the spores as readily.

Answer: Pale colored

MacConkey Agar is a differential media that distinguishes between lactose-fermenting and lactose-non-fermenting bacteria. Lactose fermentation breaks down lactose sugar in the medium, producing lactic acid which lowers the pH and causes a color indicator in the media to turn pink or red. Pseudomonas species are lactose non-fermenters, so they will not change the pH of the media and will grow as colorless or pale colonies.

The other options are incorrect:

• Purple colored: This color is not typical for bacterial growth on MacConkey Agar.
• Pink colored: This color indicates lactose fermentation, which Pseudomonas does not perform.
• Green colored: While some Pseudomonas species can produce pigments, MacConkey Agar doesn’t typically promote this pigment production, resulting in colorless colonies.

Answer: Crystal violet

Crystal violet is the primary stain used in the Gram stain procedure. Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, which traps the crystal violet stain during the staining process. This results in gram-positive bacteria appearing purple under a microscope.

The other options are incorrect:

• Fast green: Fast green is a counterstain sometimes used in other staining techniques, but not in the Gram stain.
• Haematoxylon: Haematoxylon is a nuclear stain commonly used in histology for staining tissues. It’s not used in bacterial staining techniques like the Gram stain.
• Safranin: Safranin is a counterstain used in the Gram stain on gram-negative bacteria. Since gram-positive bacteria retain the crystal violet, safranin doesn’t play a role in their staining.

Answer: Chlorophyll + phycobilin

Red algae contain a combination of pigments that contribute to their final color. They have chlorophyll a (essential for photosynthesis) but lack chlorophyll b. However, the most distinctive pigment responsible for their red hue is a group called phycobilins. Specifically, phycoerythrin is the main phycobilin that absorbs blue light and reflects red light, giving red algae their characteristic color.

The other options are incorrect:

• Rhodochrome: While there are pigments called rhodochromes, they are not typically found in red algae.
• Fucoxanthin: Fucoxanthin is a brown-colored pigment found in brown algae, not red algae.
• Chlorophyll only: Red algae do have chlorophyll a, but it is masked by the presence of phycobilins which give the red coloration.

Answer: Lactobacillus

Lactobacillus is a genus of bacteria commonly known as lactic acid bacteria (LAB). These bacteria are widely used in the food industry for fermenting various products, including dairy milk. During milk fermentation, Lactobacillus converts lactose sugar in the milk into lactic acid. This acidification process thickens the milk (curd formation) and contributes to the tangy flavor of fermented dairy products like yogurt, cheese, and buttermilk.

The other options are incorrect:

• Azetobacter: These bacteria are known for converting alcohol into acetic acid (vinegar) through a process called aerobic respiration. They are not typically used in dairy fermentation.
• Rhizobium: These bacteria are nitrogen-fixing bacteria found in root nodules of leguminous plants. They have no role in dairy fermentation.
• Hay bacillus: This term is not a specific bacterial genus and likely refers to Bacillus species commonly found in soil and hay. While some Bacillus species can ferment various substrates, they are not typically used for controlled dairy fermentation due to their diverse metabolic capabilities, which might not be desirable in the final product.

Answer: Systemic mycoses

Systemic mycoses are fungal infections that affect the internal organs and can spread throughout the body, often via the bloodstream or lymphatic system. These infections typically originate from the lungs or skin and can disseminate to other organs, leading to serious health complications.

The other options are incorrect:

• Mycoses: Mycoses is a general term referring to any fungal infection. While some mycoses can affect internal organs, the term does not specifically denote systemic infections.
• Mycotoxicosis: Mycotoxicosis refers to poisoning caused by ingestion of fungal toxins (mycotoxins) present in contaminated food or feed. It is not a term used to describe fungal infections affecting internal organs.
• Superficial mycoses: Superficial mycoses are fungal infections limited to the outer layers of the skin, hair, and nails. They do not typically involve internal organs or spread throughout the body like systemic mycoses.

Answer: Alberts stain

Albert’s stain is a specific staining technique designed to visualize the metachromatic granules present in Corynebacterium species, particularly Corynebacterium diphtheriae, the causative agent of diphtheria. The stain highlights these granules with a distinct purple-black color against a light green background.

The other options are incorrect:

• Giemsa stain: Giemsa stain is a versatile stain used for various purposes, including identifying different cell types and parasites within a sample. It’s not specifically designed for metachromatic granules in Corynebacterium.
• Acid-fast staining: This staining technique is used to identify bacteria with a thick waxy cell wall, like Mycobacterium tuberculosis. It wouldn’t be effective for staining Corynebacterium’s metachromatic granules.
• Both Giemsa stain and Alberts stain: While Giemsa stain can be used for some bacteria, Albert’s stain is the preferred and more specific choice for highlighting metachromatic granules in Corynebacterium.