Microbiology MCQs with Answer and Explnation | Chapter 3

Answer: Parter & Richet

Richet and Portier were French physiologists who were studying the effects of sea anemone venom on dogs. They found that dogs that were injected with a small amount of venom developed immunity to the venom. However, when the dogs were injected with a second dose of venom, they developed a severe allergic reaction, which Richet called “anaphylaxis.“

Richet and Portier’s discovery of anaphylaxis was a major breakthrough in the understanding of allergic reactions. It showed that the immune system can overreact to certain allergens, which can lead to life-threatening consequences.

• Coombs and Gell developed the Coombs test, which is used to diagnose autoimmune hemolytic anemia.

Answer: Escherich

Escherich was a German pediatrician who was studying the intestinal bacteria of infants. He isolated E. coli from the feces of healthy infants and showed that it was different from other known bacteria. He named the bacterium Bacterium coli commune, but it is now known as Escherichia coli.

Escherich’s work was important because it helped to establish that bacteria can be both beneficial and harmful. He also showed that E. coli is a normal inhabitant of the human intestine and that it plays a role in digestion.

E. coli is now one of the most well-studied bacteria in the world. It is used as a model organism in many areas of research, including microbiology, genetics, and biochemistry.

Answer: None of the above

Gene expression: Plasmids can carry genes that can be expressed in the host cell. This can be used to produce proteins of interest, such as enzymes or hormones.
Antibiotic resistance: Some plasmids carry genes that make the host cell resistant to antibiotics. This can be a problem in hospitals, where bacteria can acquire antibiotic resistance plasmids from other bacteria.
Conjugation: Some plasmids can be transferred from one bacterium to another through a process called conjugation. This can allow bacteria to share genes with each other, even if they are different species.
Virulence: Some plasmids carry genes that make the host cell more virulent, or disease-causing. These genes may encode toxins or other factors that help the bacteria to invade and infect cells.
Plasmids are not essential for bacterial survival, but they can provide bacteria with a number of advantages, such as the ability to produce new proteins, resist antibiotics, and transfer genes to other bacteria.

Answer: Exaltation

Virulence is the ability of a pathogen to cause disease. Exaltation is the process of increasing the virulence of a pathogen. Exalted pathogens are more likely to cause severe disease than non-exalted pathogens.

There are a number of ways that pathogens can become exalted. For example, pathogens can become exalted by:

• Mutation: Genetically modifying the pathogen to increase its virulence.
• Acquisition of new genes: Acquiring new genes from other pathogens or from the environment that can increase virulence.
• Adaptation to the host: Adapting to the host’s immune system, which can make it more difficult for the host to fight off the infection.

Answer: Lipolytic organisms

Rancidity in spoiled foods is due to lipolytic organisms.

Lipolytic organisms are microorganisms that produce enzymes that break down lipids (fats and oils). This process, called lipolysis, releases free fatty acids, which can cause food to have a rancid smell and taste.

Lipolytic organisms are commonly found in soil and water, and can also be found in food products, such as meat, dairy products, and nuts. When food is not properly stored or processed, lipolytic organisms can grow and produce lipolytic enzymes. This can lead to rancidity, even if the food is not otherwise spoiled.

• Proteolytic organisms break down proteins, which can cause food to spoil, but they do not cause rancidity.
• Toxigenic microbes produce toxins, which can make food unsafe to eat, but they do not cause rancidity.
• Saccharolytic microbes break down carbohydrates, which can cause food to ferment, but they do not cause rancidity.

Answer: Direct contact transmission

The term for when a person can be infected by direct contact with infected tissue of another person is direct contact transmission.

Direct contact transmission occurs when an infected person’s bodily fluids or tissues come into contact with another person’s skin or mucous membranes. This can happen through touching, kissing, sexual contact, or contact with blood or other bodily fluids.

Examples of diseases that can be transmitted through direct contact include:

• Common cold
• Flu
• Meningitis
• HIV
• Herpes
• Hepatitis B
• Hepatitis C
• Tuberculosis

It is important to practice good hygiene to prevent the spread of diseases that can be transmitted through direct contact. This includes washing your hands frequently, avoiding contact with sick people, and using condoms during sexual intercourse.

Other options:

• Indirect contact transmission: This occurs when a person is infected through contact with a contaminated object or surface.
• Attachment: This is the process by which a pathogen adheres to a cell in order to infect it.

Answer: Elie Metchnikoff

Metchnikoff was a Russian microbiologist who is considered to be one of the founders of immunology. He was the first to discover that white blood cells, known as phagocytes, can engulf and destroy bacteria. This discovery led to his development of the phagocytic theory of immunity, which states that phagocytes play a central role in the body’s defense against infection.

Metchnikoff’s work on phagocytosis was revolutionary for its time. It challenged the prevailing belief that the body’s immune response was mediated by humoral factors, such as antibodies. Metchnikoff’s work laid the foundation for our understanding of the innate immune system, and it has had a significant impact on the development of vaccines and other treatments for infectious diseases.

• Louis Pasteur was a French microbiologist who is known for his work on vaccines and pasteurization.
• Emil von Behring was a German microbiologist who is known for his work on diphtheria and tetanus antitoxins.
• Alexander Widal was a French physician and microbiologist who is known for his development of the Widal test for typhoid fever.

Answer: Chemostat

A chemostat is an apparatus used in microbiology and biotechnology to maintain a continuous culture of microorganisms. It allows for the controlled growth of microorganisms by continuously supplying fresh nutrient media while removing an equal amount of spent media to maintain a constant volume. This process ensures a steady-state environment where microbial growth can be sustained for an extended period.

Here is a more detailed explanation of why the other options are incorrect:

• Both Chemostat and Thermostat: While thermostats are used in some continuous culture systems, they are not essential for maintaining a continuous culture. Chemostats, on the other hand, are essential for maintaining a continuous culture.
• Autostat: Autostats are used to maintain a constant pH in a liquid culture, not a constant cell density.
• Thermostat: Thermostats are used to maintain a constant temperature, not a constant cell density.

Answer: Corynebacterium

Corynebacterium diphtheriae is a gram-positive, rod-shaped bacterium that can produce a toxin that is responsible for the symptoms of diphtheria. The toxin can damage the tissues of the throat, nose, and larynx, making it difficult to breathe and swallow. In severe cases, the toxin can also damage the heart and other organs.

• Staphylococcus and Streptococcus are also genera of gram-positive bacteria, but they are not known to cause diphtheria.

Answer: Marrice Arthus

he Arthus reaction was discovered by Nicolas Maurice Arthus in 1903. He was a French immunologist who studied the effects of foreign proteins on the body. Arthus found that repeated injections of horse serum into rabbits resulted in a severe inflammatory reaction at the injection site. This reaction was later named the Arthus reaction.

The other answer choices are incorrect:

• Richet: Charles Richet was a French physiologist who discovered anaphylaxis, a type I hypersensitivity reaction.
• Von Pirquet: Clemens von Pirquet was an Austrian pediatrician who developed the Pirquet test, a skin test for tuberculosis.
• Porter: Rodney Porter was a British biochemist who shared the 1972 Nobel Prize in Physiology or Medicine for his work on the structure of antibodies.

Answer: All of these

The primary mediators in anaphylaxis are “Histamine,” “Serotonin,” and “Heparin.” These substances are released in response to an allergic or hypersensitivity reaction. Histamine and serotonin cause blood vessel dilation and increased vascular permeability, leading to symptoms such as hives, swelling, and low blood pressure. Heparin prevents blood clotting, aiding in the body’s response to the allergen. Together, these mediators contribute to the hallmark symptoms of anaphylaxis.

• Histamine: Histamine is a potent vasodilator that also causes smooth muscle contraction. It is responsible for many of the skin and respiratory symptoms of anaphylaxis.
• Tryptase: Tryptase is a protease that can break down a number of important proteins in the body. It is thought to contribute to the vascular leak and tissue damage that can occur in anaphylaxis.
• Leukotrienes: Leukotrienes are potent bronchoconstrictors that can also cause inflammation. They are thought to contribute to the respiratory symptoms of anaphylaxis.
• Prostaglandins: Prostaglandins are a group of eicosanoids that have a variety of biological effects, including vasoconstriction, bronchoconstriction, and inflammation. They are thought to contribute to the cardiovascular and respiratory symptoms of anaphylaxis.
• TNF-α: TNF-α is a proinflammatory cytokine that is thought to contribute to the late-phase reaction in anaphylaxis.
• PAF: PAF is a phospholipid that is a potent activator of platelets and neutrophils. It is thought to contribute to the cardiovascular and respiratory symptoms of anaphylaxis.

Answer: B 850 & B 875

n most purple bacteria, the light harvesting centers are B 850 and B 875. These are bacteriochlorophyll a (Bchl a) pigment-protein complexes that are responsible for capturing light energy and transferring it to the reaction center, where photosynthesis takes place.

B 850 and B 875 are arranged in a ring-like structure around the reaction center. This arrangement allows for efficient transfer of light energy from the B 850 and B 875 complexes to the reaction center.

The other answer choices are incorrect:

• B 850 & Fe-S: Fe-S clusters are involved in electron transfer reactions, but they are not part of the light harvesting centers.
• B 845 & B 875: B 845 is a bacteriochlorophyll b (Bchl b) pigment-protein complex that is found in some purple bacteria, but it is not as common as B 850 and B 8775.
• B 850 & B830: B 830 is a bacteriochlorophyll c (Bchl c) pigment-protein complex that is found in green sulfur bacteria. It is not found in purple bacteria.

Answer: Sir Alexander Ogston

Staphylococcus aureus was isolated by Sir Alexander Ogston in 1880.

Ogston was a Scottish surgeon who was studying the pus from abscesses. He isolated the bacteria from the pus and showed that it was different from other known bacteria. He named the bacteria Micrococcus aureus, but it is now known as Staphylococcus aureus.

Staphylococcus aureus is a major human pathogen that can cause a variety of diseases, including skin infections, wound infections, pneumonia, and sepsis. It is also a common cause of food poisoning.

The other options are not correct:

• Rosenbach isolated Staphylococcus epidermidis, a less common but still important human pathogen.
• Louis Pasteur is best known for his work on rabies and vaccines.
• Passet isolated Bacillus subtilis, a non-pathogenic bacterium that is used in a variety of industrial applications.

Answer: Schaudinn and Hoffman

Treponema pallidum, the bacterium that causes syphilis, was first discovered by German scientists Fritz Schaudinn and Erich Hoffmann in 1905. They identified the bacterium using dark-field microscopy, a technique that allows for the visualization of unstained microorganisms.

Schaudinn and Hoffmann’s discovery was a major breakthrough in the understanding of syphilis, as it provided a definitive cause for the disease and paved the way for the development of effective treatments.

The other answer choices are incorrect:

• Robert Koch: Robert Koch was a German physician and microbiologist who discovered the bacteria that cause tuberculosis and cholera. He is also known for developing the Koch’s postulates, a set of criteria that are used to establish a causal relationship between a microorganism and a disease.
• Edward Jenner: Edward Jenner was an English physician who developed the smallpox vaccine. He is considered to be the father of immunology.
• Louis Pasteur: Louis Pasteur was a French scientist who made significant contributions to the fields of microbiology and immunology. He is credited with developing the rabies vaccine and the pasteurization process.

Answer: Indole Test

Indole is a product of tryptophan deamination. Tryptophan is an amino acid that is found in many proteins. When bacteria deaminate tryptophan, they produce indole. Indole is a brown-colored substance that can be detected using the indole test.

To perform the indole test, a small amount of bacterial culture is added to a tube of medium containing tryptophan. The tube is then incubated at 37 degrees Celsius for 24 hours. After incubation, the tube is examined for the presence of a brown-colored ring at the top of the medium. If a brown ring is present, the test is positive, indicating that the bacteria have deaminated tryptophan.

The other answer choices are incorrect:

• The lactose test is used to detect the fermentation of lactose, a sugar found in milk.
• The proteolytic test is used to detect the ability of bacteria to break down proteins.
• The Nessler’s reagent test is used to detect the presence of ammonia.

Answer: Cell membrane

In Streptococcus fecalis, conjugation takes place at the cell membrane. Conjugation is a type of horizontal gene transfer in which genetic material is transferred from one bacterial cell to another. During conjugation, two bacterial cells come into contact with each other, and a pilus, or sex pilus, is formed between the two cells. The pilus serves as a bridge for the transfer of DNA from the donor cell to the recipient cell.

The other answer choices are incorrect:

• Pili are hair-like appendages that are found on the surface of many bacteria. They are used for attachment to surfaces and for motility.
• The cell wall is a rigid layer that surrounds the bacterial cell membrane. It provides protection and support for the cell.
• Flagella are whip-like appendages that are used for bacterial motility.

Answer: Prions

Prions are infectious proteins that lack genetic material. They are thought to cause disease by misfolding other proteins in the body, which can lead to the formation of amyloid plaques. Amyloid plaques are the hallmark of many neurodegenerative diseases, such as Alzheimer’s disease and Parkinson’s disease.

Prion diseases can affect humans and animals. Some examples of prion diseases include.

• Mad cow disease (bovine spongiform encephalopathy, BSE)
• Scrapie (in sheep and goats)
• Chronic wasting disease (in deer and elk)
• Kuru and Creutzfeldt-Jakob disease (in humans)

The other answer choices are incorrect:

• Virons are viruses. Viruses are infectious agents that contain nucleic acid and can replicate in cells.
• Nucleoids are the regions of bacteria and archaea that contain their genetic material.

Answer: Robert Koch

Koch was a German physician and microbiologist who is known for his work on infectious diseases. He developed a set of criteria, known as Koch’s postulates, for proving that a particular microorganism is the cause of a particular disease.

Koch used his own postulates to prove that Mycobacterium tuberculosis is the cause of tuberculosis. He isolated the bacteria from the lungs of people who had died from tuberculosis and grew it in pure culture. He then inoculated the bacteria into animals, which developed tuberculosis.

Koch’s discovery of Mycobacterium tuberculosis was a major breakthrough in the fight against tuberculosis. It led to the development of new diagnostic tests and treatments for the disease.

The other answer choices are incorrect:

• Louis Pasteur: Louis Pasteur was a French scientist who made significant contributions to the fields of microbiology and immunology. He is credited with developing the rabies vaccine and the pasteurization process.
• Edward Jenner: Edward Jenner was an English physician who developed the smallpox vaccine. He is considered to be the father of immunology.

Answer: Schaudinn and Hoffman

The correct answer is Schaudinn and Hoffmann. Fritz Schaudinn and Erich Hoffmann were German scientists who discovered Treponema pallidum, the bacterium that causes syphilis, in 1905. Using dark-field microscopy, they identified the bacterium in the lesions of syphilitic patients. Their discovery was a major breakthrough in the understanding and treatment of syphilis.

Here is a summary of the achievements of the scientists mentioned in the answer choices:

• Louis Pasteur: Louis Pasteur was a French scientist who made significant contributions to the fields of microbiology and immunology. He is credited with developing the rabies vaccine and the pasteurization process.
• Laennec: René-Théophile-Hyacinthe Laennec was a French physician who invented the stethoscope in 1816.
• Burgey: George Burgey was an American bacteriologist who made significant contributions to the study of staphylococci and streptococci.

Answer: E.coli

E.coli is a Gram-negative, chemolithotrophic bacterium that is commonly found in the human intestine. It is a facultative anaerobe, meaning that it can grow in the presence or absence of oxygen. E.coli is a member of the Enterobacteriaceae family, which includes many other important pathogens, such as Salmonella and Shigella.

The other answer choices are incorrect:

• Mycoplasms: Mycoplasms are Gram-negative, chemoheterotrophic bacteria that are the smallest known bacteria. They lack a cell wall, which makes them difficult to stain with Gram stain.
• Spirillum: Spirochetes are Gram-negative, chemoheterotrophic bacteria that are known for their spiral shape. They are motile, meaning that they can move on their own.
• Siderococcus: Siderococci are Gram-positive, chemoheterotrophic bacteria that are found in soil and water. They are able to fix nitrogen, which means that they can convert atmospheric nitrogen into a form that can be used by plants.

Answer: Neurotoxin

The etiologic agent of botulism is a neurotoxin.

It is a protein that is produced by the bacterium Clostridium botulinum. The neurotoxin blocks the release of acetylcholine, a neurotransmitter that is essential for muscle contraction. This can lead to muscle paralysis, including paralysis of the respiratory muscles, which can be fatal.

The neurotoxin is produced in food when Clostridium botulinum spores germinate and grow. This can happen in food that is improperly canned or preserved. The neurotoxin can also be produced in the intestines of infants and in wounds.

There are seven types of botulinum neurotoxin (A, B, C, D, E, F, and G). Types A, B, E, and F can cause human botulism. Types C and D can cause botulism in animals.

Botulism is a rare but serious disease. Treatment involves administering antitoxin to neutralize the neurotoxin and supportive care to maintain breathing and other vital functions.

Answer: Neisser in 1879

Neisseria gonorrhoeae was first described by Albert Neisser in 1879. He was a German physician and bacteriologist who identified and named the bacterium responsible for the sexually transmitted infection gonorrhea.

The other answer choices are incorrect:

• Pasteur in 1878: Louis Pasteur, a French scientist, made significant contributions to the fields of microbiology and immunology. He is credited with developing the rabies vaccine and the pasteurization process.
• Robert Koch: Robert Koch, a German physician and microbiologist, discovered several important pathogens, including Mycobacterium tuberculosis, the bacterium that causes tuberculosis.

Answer: Haemophilus influenza

Among the options provided, the bacterium Haemophilus influenzae can cause symptoms resembling a cold. While it’s primarily associated with more serious respiratory infections like pneumonia, it can also contribute to conditions such as sinusitis and bronchitis, which might present with symptoms similar to those of a common cold. These symptoms can include nasal congestion, coughing, sore throat, and sometimes fever.

Answer: Pandemic

A pandemic is a global outbreak of disease. It is an epidemic that has spread across multiple countries or continents. Pandemics are typically caused by viruses, such as the flu virus or the coronavirus that causes COVID-19.

Other options:

• Sporadic: This means that the disease occurs occasionally and irregularly.
• Epidemic: This means that the disease is widespread in a community or region.
• Endemic: This means that the disease is constantly present in a community or region.

Answer: Negri bodies

Negri bodies are inclusion bodies found in the cytoplasm of neurons of animals infected with rabies virus. They are eosinophilic and basophilic, and they have a distinct morphology that makes them easy to identify under a microscope. Negri bodies are considered to be the hallmark of rabies infection, and they are used to diagnose the disease.

The other answer choices are incorrect:

• Niagri bodies: This is a misspelling of Negri bodies.
• Neisser bodies: Neisser bodies are bacterial inclusion bodies that are found in the cytoplasm of cells infected with Neisseria gonorrhoeae, the bacterium that causes gonorrhea.
• Nergi bodies: This is another misspelling of Negri bodies.

Answer: Escherichia

The bacterium most commonly used in genetic engineering is Escherichia coli (E. coli). E. coli has been extensively studied and is widely used in biotechnology and genetic engineering due to several factors: its rapid growth, well-understood genetics, ease of manipulation, and the ability to express foreign genes. These characteristics make it a popular choice as a host organism for the production of various proteins, enzymes, and for the replication of recombinant DNA molecules in laboratories.

The other answer choices are incorrect:

• Klebsiella: Klebsiella is a Gram-negative, rod-shaped bacterium that is also found in the human intestine. However, it is not as commonly used in genetic engineering as E. coli.
• Serratia: Serratia is another Gram-negative, rod-shaped bacterium that is found in the environment. It is sometimes used in genetic engineering, but it is not as popular as E. coli.
• Proteus: Proteus is a Gram-negative, motile bacterium that is found in soil and water. It is not commonly used in genetic engineering.

Answer: Lippolysacharide

LPS is a complex molecule that consists of three parts: a lipid A core, an inner core, and an O-polysaccharide chain. The lipid A core is responsible for the endotoxic activity of LPS. It is released when the bacterium dies or lyses, and it can cause a variety of harmful effects, including fever, inflammation, and shock.

The other options are not correct:

• Peptidoglycan is a component of the cell wall of both Gram-negative and Gram-positive bacteria.
• Teichoic acid is a component of the cell wall of Gram-positive bacteria.
• The inner membrane is a phospholipid bilayer that separates the cytoplasm of the bacterium from the periplasmic space. It is not involved in the production or release of LPS.

Answer: All of the above

Virulence factors are molecules or structures that enable a pathogen to cause disease. They play a crucial role in the progression of an infection by allowing the pathogen to attach to and invade host cells, evade the host’s immune system, and produce toxins or enzymes that damage host tissues.

• Adhesions: Adhesins are molecules on the surface of a pathogen that allow it to attach to host cells. This attachment is essential for the pathogen to colonize the host and cause infection.
• Invasiveness: Invasiveness is the ability of a pathogen to enter host cells. This can be achieved through a variety of mechanisms, such as the production of enzymes that break down the cell wall or the use of internalin proteins to zipper the pathogen’s membrane to the host cell’s membrane.
• Enzymes: Enzymes are proteins that catalyze biochemical reactions. Some pathogens produce enzymes that can damage host tissues or interfere with normal cellular processes. For example, the enzyme collagenase breaks down collagen, a protein that is important for structural support, while the enzyme hemolysin lyse red blood cells.
• Toxigenicity: Toxigenicity is the ability of a pathogen to produce toxins. Toxins are poisonous substances that can damage host tissues or interfere with normal cellular processes. For example, the toxin botulinum toxin causes paralysis, while the toxin tetanus toxin causes muscle spasms.

Answer: LD50

The lethal dose required to kill 50% of the lab animals tested under standard conditions is referred to as LD50 (Lethal Dose 50). LD50 is a standard measure used in toxicology and pharmacology to assess the potency or toxicity of a substance or compound.

The other answer choices are incorrect:

• ID50: ID50 stands for “Infectious Dose 50”. It is the amount of a virus or bacterium that is required to infect 50% of a group of test animals.
• MLD: MLD stands for “Median Lethal Dose”. It is the amount of a substance that will kill 50% of a group of test animals within a specified period of time, usually 24 hours.
• ID: ID stands for “Infectious Dose”. It is the amount of a virus or bacterium that is required to cause an infection.

Answer: Avery Macleod & Mc.Carthy

The transfer of genetic material during transformation was further demonstrated and confirmed by the experiments of Avery, MacLeod, and McCarty. Their work, building upon Griffith’s experiment, conclusively identified that DNA (deoxyribonucleic acid) was the substance responsible for carrying genetic information and could be transferred between bacterial cells, thus providing substantial evidence supporting the concept of DNA as the hereditary material.

The other answer choices are incorrect:

• Zinder and Lederberg: Zinder and Lederberg discovered that bacteriophages, or viruses that infect bacteria, can transfer genetic material between bacteria. However, they did not provide evidence that DNA is the transforming principle.
• Watson and Crick: Watson and Crick discovered the structure of DNA in 1953. This discovery was important for understanding how DNA stores and transmits information, but it did not directly prove that DNA is the transforming principle.
• Lederberg and Tatum: Lederberg and Tatum discovered that bacteria can exchange genetic material through a process called conjugation. This discovery was also important for understanding bacterial genetics, but it did not directly prove that DNA is the transforming principle.

Answer: Mechanical vectors

Mechanical vectors do not become infected with the pathogen themselves. Instead, they pick up the pathogen on their bodies while feeding on an infected host, and then transfer it to a new host when they feed again.

Examples of mechanical vectors include flies, mosquitoes, and cockroaches. These insects can transmit a variety of diseases, including typhoid fever, cholera, and dysentery.

Other options:

• Biological vectors: These vectors become infected with the pathogen themselves and then transmit it to a new host when they bite or inject the pathogen into the host. Examples of biological vectors include mosquitoes and ticks.
• Biological reservoir: This is an organism that harbors a pathogen and can transmit it to another organism. Examples of biological reservoirs include humans, animals, and plants.

Answer: Frank

Frank is the correct answer. Albert Bernhard Frank, a German botanist, first observed mycorrhiza in 1885. He was studying the roots of tree seedlings and noticed that they were covered in a fungal-like growth. He gave this growth the name “mycorrhiza,” which means “fungus root.”

Frank’s discovery was a major breakthrough in our understanding of plant nutrition. Mycorrhizae are now known to be essential for the health of many plants, especially trees. They help plants to absorb nutrients from the soil, such as phosphorus and nitrogen, and they also protect plants from disease.

The other answer choices are incorrect:

• Crick: Francis Crick was a British molecular biologist who is best known for co-discovering the structure of DNA in 1953.
• Fisher: George Fisher was an American bacteriologist who made significant contributions to the study of tuberculosis.
• Funk: Isaac Funk was an American publisher who founded the Funk & Wagnalls company.

Answer: Coxiella

Among the options listed, Coxiella is the genus most likely to contain organisms capable of surviving high temperatures. Coxiella burnetii, the species within the Coxiella genus, is known for its ability to withstand extreme conditions, including high temperatures. This bacterium is the causative agent of Q fever and can survive in harsh environments, including those with high temperatures and pressures, as well as in acidic conditions.

• orula is a genus of yeasts, and most yeasts are not able to survive at temperatures above 50°C (122°F).
• Vibrio is a genus of bacteria that includes some species that are able to tolerate high temperatures, such as Vibrio cholerae, which causes cholera. However, most Vibrio species are not able to survive at temperatures above 60°C (140°F).
• Pseudomonas is a genus of bacteria that is very diverse, and some species are able to tolerate high temperatures, while others are not. However, in general, Pseudomonas species are not as heat-resistant as Coxiella species.

Answer: Hansen

Mycobacterium leprae, the bacterium that causes leprosy, was discovered by Gerhard Armauer Hansen in 1873. He was a Norwegian physician who identified and described the bacterium responsible for the disease, making significant contributions to the understanding and recognition of leprosy as a bacterial infection.

The other answer choices are incorrect:

• Edward Jenner: Edward Jenner was an English physician who developed the smallpox vaccine.
• Louis Pasteur: Louis Pasteur was a French scientist who made significant contributions to the fields of microbiology and immunology.
• Robert Koch: Robert Koch was a German physician and microbiologist who discovered several important pathogens, including Mycobacterium tuberculosis, the bacterium that causes tuberculosis.

Answer: Louis Pasteur

The bacterium Streptococcus pneumoniae was first isolated and identified by Louis Pasteur in 1880. Pasteur was a French scientist who made significant contributions to the fields of microbiology and immunology. He is credited with developing the rabies vaccine and the pasteurization process.

The other answer choices are incorrect:

• Edward Jenner: Edward Jenner was an English physician who developed the smallpox vaccine.
• Robert Koch: Robert Koch was a German physician and microbiologist who discovered several important pathogens, including Mycobacterium tuberculosis, the bacterium that causes tuberculosis.
• Antony van Leewenhoek: Antony van Leeuwenhoek was a Dutch scientist who is considered to be the “father of microbiology.” He is best known for his invention of the microscope, which allowed him to observe and describe microorganisms for the first time.

Answer: All of These

Both quinine sulfate and auramine are fluorescent substances used in fluorescent microscopy:

• Quinine sulfate: This substance, derived from the bark of the cinchona tree, has fluorescent properties and has historically been used in fluorescent microscopy.
• Auramine: It’s a fluorescent dye commonly used in the visualization of acid-fast bacteria like Mycobacterium tuberculosis in microscopy.

Answer: Co-factors of enzymes

The major role of minor elements (often referred to as trace elements or micronutrients) inside living organisms is primarily to act as co-factors of enzymes. These elements are essential for the proper functioning of enzymes, often serving as co-factors or coenzymes that facilitate enzyme activity. They assist in catalyzing biochemical reactions necessary for various metabolic processes within the cell. While these elements might also play roles in other cellular functions, their primary significance lies in supporting enzymatic reactions.

The other answer choices are incorrect:

• Constituents of hormones: Hormones are signaling molecules that regulate a variety of physiological processes. While some hormones do contain minor elements, these elements are not essential for their function.
• Binder of cell structure: Cell structure is maintained by a variety of proteins and other molecules. Minor elements can play a role in binding these molecules together, but this is not their primary function.
• Building blocks of important amino acids: Amino acids are the building blocks of proteins. While some amino acids do contain minor elements, these elements are not essential for their structure or function.

Answer: Schroeter and Gessard

Pseudomonas aeruginosa was first named by Schroeter and Gessard in the 19th century. These scientists were among the early researchers who identified and characterized this bacterium.

The other answer choices are incorrect:

• Edward Jenner: Edward Jenner was an English physician who developed the smallpox vaccine.
• Louis Pasteur: Louis Pasteur was a French scientist who made significant contributions to the fields of microbiology and immunology.
• Robert Koch: Robert Koch was a German physician and microbiologist who discovered several important pathogens, including Mycobacterium tuberculosis, the bacterium that causes tuberculosis.

Answer: Invasiveness

The ability of a pathogen to spread in the host tissues after establishing the infection is known as invasiveness. This characteristic refers to the pathogen’s capacity to penetrate and move within the host’s tissues beyond the initial site of infection, potentially leading to more extensive colonization and the potential for systemic infection.

The other answer choices are incorrect:

• Adhesion: Adhesion is the ability of a pathogen to attach to host cells, which is an initial step in the infection process but does not necessarily lead to invasion.
• Toxigenicity: Toxigenicity is the ability of a pathogen to produce toxins, which can damage host cells and tissues but do not directly contribute to invasion.

Answer: Attenuation

The reduction of virulence in a pathogen is known as attenuation. Attenuation refers to the process by which a pathogen’s virulence or disease-causing ability is decreased or weakened, often intentionally, to create vaccines or weakened strains for study. This weakened state allows the pathogen to be used safely in vaccine development or research while still eliciting an immune response without causing severe disease.

The other answer choices are incorrect:

• Exaltation: Exaltation is the opposite of attenuation, and it refers to an increase in a pathogen’s virulence. This can occur through natural selection or through genetic manipulation.
• None of these: While attenuation is the most specific term for the reduction of virulence, other terms, such as “weakening” or “modification,” can also be used in a broader sense.

Answer: Fail to reproduce on artificial meida

Mycoplasmas are the smallest and simplest self-replicating bacteria. They lack a cell wall, which makes them osmotically sensitive and difficult to cultivate in the laboratory. Mycoplasmas require specialized media that contain sterols and other nutrients that are not found in standard growth media.

The other answer choices are incorrect:

• Are resistant to penicillin: Mycoplasmas are susceptible to penicillin and other antibiotics that target bacterial cell walls.
• Stain well with Gram’s stain: Mycoplasmas do not stain well with Gram’s stain because they lack a cell wall. They are typically classified as Gram-negative bacteria, but they do not retain the Gram stain dye.
• Have a rigid cell wall: Mycoplasmas are unique among bacteria in that they lack a cell wall. This makes them very flexible and resistant to osmotic stress.

Answer: Landsteiner and Weiner

The Rh factor of the blood was discovered by Karl Landsteiner and Alexander S. Wiener. They identified the Rh factor in the mid-20th century, expanding on Landsteiner’s earlier work in blood typing and the discovery of ABO blood groups. Their research led to the identification of the Rh factor, which plays a crucial role in blood transfusions and maternal-fetal compatibility.

The other answer choices are incorrect:

• Moss: William Moss was an English physician who made significant contributions to the study of malaria.
• Janskey: Karl Landsteiner was an Austrian biologist who first described the ABO blood group system in 1901.
• Louis Pasteur: Louis Pasteur was a French scientist who made significant contributions to the fields of microbiology and immunology.

Answer: Log

Bacterial cells are typically at their metabolic peak during the log (logarithmic or exponential) phase of growth. This phase is characterized by rapid and exponential growth as the bacteria actively divide and reproduce, utilizing available nutrients optimally. The metabolic activity and growth rate are at their highest during this phase before the population growth starts to plateau in the stationary phase due to nutrient depletion and accumulation of waste products.

The other phases of bacterial growth are:

• Lag phase: The lag phase is a period of slow growth or no growth at all. During this phase, the cells are adapting to their new environment and preparing for exponential growth.
• Stationary phase: The stationary phase is a period in which the growth rate of the cells slows down or stops altogether. This can happen due to a lack of nutrients, a buildup of waste products, or other environmental factors.
• Decline phase: The decline phase is a period in which the cells begin to die. This can happen due to a lack of nutrients, a buildup of waste products, or other environmental factors.

Answer: Kochler & Milston

The hybridoma technique was developed by Köhler and Milstein. They introduced this revolutionary method in the mid-1970s, leading to the production of monoclonal antibodies. This technique involves the fusion of antibody-producing B lymphocytes with immortalized myeloma cells, creating hybrid cells called hybridomas capable of producing a specific type of antibody indefinitely.

The other answer choices are incorrect:

• Niel’s Jerne: Niels Kaj Jerne was a Danish immunologist who made significant contributions to our understanding of the immune system. He is best known for developing the network theory of the immune system.

Answer: Primary electrons

Secondary electrons are produced when the primary electron beam interacts with the atoms in the specimen. The primary electron beam knocks electrons out of the atoms in the specimen, and these electrons are then ejected from the specimen.

• Secondary electrons are used to create images in scanning electron microscopes (SEMs). SEMs use a focused electron beam to scan the surface of a specimen. The secondary electrons that are ejected from the specimen are detected and used to create an image of the surface of the specimen.
• Primary electrons are the electrons that are emitted from the tungsten filament in the electron microscope. They are accelerated through a vacuum and focused by magnetic lenses onto the specimen.
• Tertiary electrons are produced when secondary electrons interact with the atoms in the specimen. They are much less common than secondary electrons and are not used to create images in electron microscopes.

Answer: All of the above

The virulence of a pathogen is typically measured by several methods, and various parameters can be used to assess virulence. These can include:

1. LD50 (Lethal Dose 50): This measures the dose required to kill 50% of the individuals or organisms exposed to the pathogen.
2. MLD (Minimum Lethal Dose): Similar to LD50, MLD is the lowest dose of a pathogen that causes death in experimental animals.
3. ID50 (Infectious Dose 50): This measures the dose required to infect 50% of individuals or organisms exposed to the pathogen.

Answer: Von perquit

Serum sickness was discovered by Clemens von Pirquet and Béla Schick in 1906. They were Austrian and Hungarian pediatricians, respectively, who were studying the effects of antitoxin on children with diphtheria.

Von Pirquet and Schick noticed that some children who received antitoxin developed a delayed-type hypersensitivity reaction, characterized by fever, rash, joint pain, and other systemic symptoms. They called this reaction “serum sickness.”

Serum sickness is now known to be an immune complex-mediated hypersensitivity reaction that can occur in response to a variety of foreign proteins, including those found in antitoxin, vaccines, and other medications.

Answer: Binary fission

Mycoplasma typically reproduces through a process known as binary fission. This method involves the division of a single cell into two identical daughter cells. Mycoplasma lack a rigid cell wall, and during binary fission, they elongate and then split into two separate cells.

The other answer choices are incorrect:

• Binary fusion is a type of sexual reproduction in which two haploid cells fuse to form a diploid zygote. This process does not occur in mycoplasmas.
• Bursting: Bursting is a type of cell death in which the cell ruptures and releases its contents. This is not a mode of reproduction.
• Budding: Budding is a type of asexual reproduction in which a new cell grows out from the side of a parent cell. This is not a common mode of reproduction in mycoplasmas.

Answer:

Bacillus anthracis, the bacterium responsible for anthrax, was isolated by Robert Koch in 1876. Koch’s work on anthrax was crucial in establishing the principles of microbiology and demonstrating the relationship between specific bacteria and particular diseases, laying the groundwork for the germ theory of disease.

The other answer choices are incorrect:

• Leewenhoek: Antony van Leeuwenhoek was a Dutch scientist who is considered to be the “father of microbiology.” He is best known for his invention of the microscope, which allowed him to observe and describe microorganisms for the first time.
• Louis Pasteur: Louis Pasteur was a French scientist who made significant contributions to the fields of microbiology and immunology. He is credited with developing the rabies vaccine and the pasteurization process.

Answer: Hyaluronidase

Among the enzymes listed, hyaluronidase acts as a spreading factor. Hyaluronidase is an enzyme produced by certain bacteria that facilitates the degradation of hyaluronic acid, a component of connective tissue. By breaking down hyaluronic acid, hyaluronidase enables the bacteria to spread through tissues more easily by disrupting the extracellular matrix, aiding in their invasiveness.

The other answer choices are incorrect:

• DNase: DNase is an enzyme that breaks down DNA.
• Catalase: Catalase is an enzyme that breaks down hydrogen peroxide.
• Coagulase: Coagulase is an enzyme that causes blood to clot.