MicroBiology MCQs with Answer and Explnation | Chapter 21

Answer: Freeze-drying

Lyophilization, also known as freeze-drying, is a process of removing the moisture content from a product by freezing it and then subjecting it to a vacuum. This method is commonly used for preserving perishable materials, such as food and pharmaceuticals, by extending their shelf life without compromising their quality.

The other options are incorrect:

• Sterilization: Sterilization is a process that aims to eliminate or kill all forms of microbial life, including bacteria, viruses, and spores. It is not the same as lyophilization, which focuses on removing moisture.
• Burning to ashes: Burning to ashes is a destructive process that involves the combustion of materials. Lyophilization, on the other hand, is a non-destructive method that preserves the structure and quality of the material being processed.
• Exposure to formation: “Exposure to formation” is not a recognized term in the context of lyophilization or any related processes. It does not accurately describe the method of freeze-drying.

Answer: Sweating

Sweating is not an example of inflammation. Inflammation is a biological response to harmful stimuli, such as pathogens, damaged cells, or irritants. The classic signs of inflammation are pain, heat, redness, and swelling. Sweating, on the other hand, is a response of the sweat glands to regulate body temperature and is not directly related to the inflammatory process.

The other options are incorrect:

• Pain: Pain is one of the classic signs of inflammation. It occurs due to the activation of pain receptors in response to tissue damage or irritation.
• Heat: Heat is a characteristic feature of inflammation. Increased blood flow to the affected area leads to warmth, contributing to the overall inflammatory response.
• Swelling: Swelling, or edema, is a common manifestation of inflammation. It results from an accumulation of fluid and immune cells at the site of injury or infection.

Answer: Typhidot and widal tests

Typhoid fever is usually diagnosed using a combination of Typhidot and Widal tests. The Typhidot test detects specific antibodies against Salmonella typhi, the bacterium causing typhoid fever, in the blood. The Widal test measures the agglutination (clumping) of antibodies in response to antigens derived from the S. typhi bacteria. Together, these tests help in the accurate diagnosis of typhoid fever.

The other options are incorrect:

• Typhidot test: The Typhidot test is actually a correct option. It is used for diagnosing typhoid fever by detecting antibodies against S. typhi.
• Widal test: The Widal test is also a correct option. It is an agglutination test that helps identify antibodies against S. typhi and is commonly used in the diagnosis of typhoid fever.
• Precipitation test: The precipitation test is not typically used for the diagnosis of typhoid fever. Instead, the Typhidot and Widal tests are more commonly employed for this purpose.

Answer: Obligate anaerobe

Clostridium bacillus is an obligate anaerobe. This means that it is a microorganism that thrives in the absence of oxygen. Obligate anaerobes are unable to grow or survive in the presence of oxygen and may even be killed by exposure to it. Clostridium species, including Clostridium bacillus, are known for their ability to form endospores and are commonly found in environments with low oxygen levels.

The other options are incorrect:

• Facultative anaerobe: Facultative anaerobes can survive in both the presence and absence of oxygen. Clostridium bacillus, however, is an obligate anaerobe and cannot tolerate oxygen.
• Facultative aerobe: Facultative aerobes can grow in the presence or absence of oxygen. Clostridium bacillus, being an obligate anaerobe, does not fall into this category.
• Obligate aerobe: Obligate aerobes require the presence of oxygen for their growth and survival. Clostridium bacillus is an obligate anaerobe and cannot thrive in the presence of oxygen.

Answer: Viridans group

α-hemolytic streptococci are also known as the Viridans group. These bacteria are characterized by their ability to cause incomplete or partial hemolysis (greenish discoloration) on blood agar plates. The Viridans streptococci include various species that are commonly found as part of the normal flora in the human mouth, throat, and gastrointestinal tract.

The other options are incorrect:

• Streptococcus pyogenes: Streptococcus pyogenes is not part of the Viridans group. It is a β-hemolytic streptococcus and is associated with complete hemolysis on blood agar plates. S. pyogenes is known for causing diseases such as strep throat and skin infections.
• Virulence group: “Virulence group” is a general term and does not specifically refer to α-hemolytic streptococci. It is not a recognized term for categorizing this group of bacteria.
• CoNS (Coagulase-Negative Staphylococci): CoNS refers to coagulase-negative staphylococci, which are a group of bacteria, not streptococci. It is unrelated to α-hemolytic streptococci, which belong to the Viridans group.

Answer: MR test and TSI test

The Methyl Red (MR) test and Triple Sugar Iron (TSI) test are used to determine glucose fermentation by bacteria. Both tests are part of a group of biochemical tests used to identify and characterize bacteria based on their metabolic pathways.

The other options are incorrect:

• Methyl Red Test: The Methyl Red test is actually a correct option. It specifically assesses the ability of bacteria to perform mixed acid fermentation of glucose.
• TSI Test: The TSI test is also a correct option. It assesses glucose fermentation as well as lactose and sucrose fermentation, gas production, and hydrogen sulfide production.
• Urease Test: The Urease test is not used to determine glucose fermentation. Instead, it tests the ability of bacteria to hydrolyze urea to produce ammonia. It is not directly related to the assessment of glucose fermentation.

Answer: Prions

Proteins particles that can cause disease are called prions. Prions are abnormal, misfolded proteins that can induce normal proteins in the brain to misfold as well. This misfolding can lead to the accumulation of protein aggregates, causing neurodegenerative diseases, such as Creutzfeldt-Jakob disease in humans and bovine spongiform encephalopathy (BSE) in cattle.

The other options are incorrect:

• Virions: Virions are complete viral particles consisting of genetic material (either DNA or RNA) surrounded by a protein coat. They are not misfolded proteins and are capable of causing infectious diseases.
• Nucleoida: “Nucleoida” is not a recognized term in the context of disease-causing proteins. It appears to be a misspelling or a term not commonly used in biological or medical contexts.
• Bacteriophages: Bacteriophages are viruses that infect bacteria. They are not misfolded proteins but rather entities with genetic material and a protein coat that can infect and replicate within bacterial cells.

Answer: Log phase

Bacteria are most sensitive to antibiotics during the log phase of the growth curve. The log phase, also known as the exponential or growth phase, is characterized by rapid cell division and active metabolic processes. During this phase, bacterial cells are actively synthesizing proteins and replicating their DNA, making them more susceptible to the actions of antibiotics that target these processes.

The other options are incorrect:

• Decline phase:The decline phase, also known as the death or logarithmic decline phase, is characterized by a decrease in the number of viable cells. Bacterial cells during this phase are less sensitive to antibiotics as their metabolic activities decline.
• Lag phase: The lag phase is an initial phase where bacteria are adapting to their environment, and there is minimal growth. During this phase, bacterial cells are not actively dividing, making them less susceptible to antibiotics.
• Stationary phase: The stationary phase is a period of equilibrium where the rate of bacterial cell division equals the rate of cell death. Bacterial cells in the stationary phase may exhibit reduced sensitivity to antibiotics due to decreased metabolic activity.

Answer: Safranin

The staining material for Gram-negative bacteria is Safranin. In the Gram staining technique, Safranin is used as the counterstain or secondary stain that helps visualize Gram-negative bacteria. Gram-negative bacteria retain the counterstain after the decolorization step, appearing pink or red under a microscope.

The other options are incorrect:

• Crystal violet: Crystal violet is the primary stain used in the Gram staining process. It initially stains all bacteria, but in the presence of iodine and alcohol, it is retained by Gram-positive bacteria.
• Carbol fuchsin: Carbol fuchsin is not typically used in the Gram staining technique. It is commonly associated with the acid-fast staining method used to detect acid-fast bacteria like Mycobacterium species.
• Methylene blue: Methylene blue is not used in the Gram staining process. It is a basic dye that is often used for staining various biological specimens but is not part of the Gram staining procedure.

Answer: Escherichia

The bacterium that is most commonly used in genetic engineering is Escherichia coli, often abbreviated as E. coli. E. coli is a gram-negative bacterium that has been extensively studied and manipulated for use in molecular biology and genetic engineering. It is a preferred host organism for the production of recombinant proteins and the cloning of genes due to its well-understood genetics, rapid growth, and ease of manipulation.

The other options are incorrect:

• Staphylococcus: Staphylococcus is not as commonly used in genetic engineering as Escherichia coli. While it has been used in certain applications, E. coli is more widely adopted in genetic engineering research and industrial processes.
• Klebsiella: Klebsiella is not as commonly used as E. coli in genetic engineering. Like other bacteria, it has been studied for various purposes, but E. coli remains the predominant choice for many genetic engineering applications.
• Proteus: Proteus is not commonly used in genetic engineering compared to E. coli. Proteus species are known for their swarming motility and are more associated with clinical infections.

Answer: Moist heat and steam under pressure

In an autoclave, the principle involved is moist heat and steam under pressure. An autoclave is a device used for sterilization by subjecting materials to high-pressure saturated steam. The combination of high pressure and moist heat ensures effective sterilization by killing bacteria, viruses, and other microorganisms, as well as inactivating spores.

The other options are incorrect:

• Dry heat: Dry heat is not the principle involved in an autoclave. Autoclaves use moist heat, which is more effective in killing microorganisms, including spores, compared to dry heat.
• Moist heat: While moist heat is a correct component, the term alone is not sufficient to describe the specific conditions created by an autoclave. Autoclaves use moist heat in the form of steam under pressure for sterilization.
• Steam under pressure: While steam under pressure is a correct component, the term alone doesn’t capture the importance of moist heat. Autoclaves use steam under pressure, but the steam is moist, and the combination with pressure is essential for effective sterilization.

Answer: PCR

Polymerase Chain Reaction (PCR) is not an example of an immuno-diagnostic test. PCR is a molecular biology technique used to amplify and analyze DNA. It is not based on the detection of antibodies or antigens, which are the principles underlying immuno-diagnostic tests.

The other options are incorrect:

• Serum plate agglutination test:The serum plate agglutination test is an immuno-diagnostic test used to detect antibodies or antigens in serum. It involves the clumping (agglutination) of particles in the presence of specific antibodies.
• ELISA (Enzyme-Linked Immunosorbent Assay): ELISA is a classic immuno-diagnostic test that involves the detection of antibodies or antigens using an enzyme-linked detection system. It is widely used in medical diagnostics and research.
• FAT (Fluorescent Antibody Test): The Fluorescent Antibody Test (FAT) is another immuno-diagnostic test that uses fluorescently labeled antibodies to detect the presence of specific antigens in tissues or specimens.

Answer: Selective

Staph-110, used for the isolation of Staphylococcus, is an example of a selective medium. Selective media are designed to encourage the growth of specific microorganisms while inhibiting the growth of others. In the case of Staph-110, the medium contains components that selectively promote the growth of Staphylococcus bacteria while suppressing the growth of other types of bacteria.

The other options are incorrect:

• Enrichment: Enrichment media are designed to increase the numbers of specific microorganisms in a sample, usually by providing nutrients that enhance the growth of the target organisms. Staph-110 is selective, not enrichment.
• Differential: Differential media are used to differentiate between different types of microorganisms based on their metabolic activities or other characteristics. Staph-110 is primarily selective, focusing on the isolation of Staphylococcus.
• General purpose: General-purpose media support the growth of a wide range of microorganisms and are not specifically designed to favor the growth of particular types. Staph-110 is selective for Staphylococcus and not a general-purpose medium.

Answer: Transcription

The production of RNA from DNA is called transcription. During transcription, the enzyme RNA polymerase reads the DNA template strand and synthesizes a complementary RNA molecule. This RNA molecule, known as messenger RNA (mRNA), carries the genetic information from the DNA to the ribosomes, where it serves as a template for protein synthesis.

The other options are incorrect:

• Translation: Translation is the process where the information carried by the mRNA is used to synthesize a protein. It occurs at the ribosomes and involves the conversion of the mRNA sequence into a corresponding amino acid sequence.
• RNA splicing: RNA splicing is a post-transcriptional process where non-coding regions (introns) are removed, and coding regions (exons) are joined together to form a mature mRNA. It is not the process of generating RNA from DNA.
• Replication: Replication is the process of copying DNA to produce an identical DNA molecule. It occurs during cell division and is not directly related to the synthesis of RNA from DNA.

Answer: Diphtheria

Metachromatic granules are found in bacteria that cause diphtheria. Diphtheria is caused by the bacterium Corynebacterium diphtheriae. Metachromatic granules are characteristic intracellular granules that stain differently from the surrounding cytoplasm, often appearing reddish or purple when subjected to certain staining techniques.

The other options are incorrect:

• Mycoplasma: Mycoplasma is a type of bacteria, but it does not typically exhibit metachromatic granules. Mycoplasma lacks a cell wall and has a distinct morphology compared to bacteria like Corynebacterium.
• Tuberculosis: Tuberculosis is caused by the bacterium Mycobacterium tuberculosis. Metachromatic granules are not a characteristic feature of Mycobacterium species.
• Tetanus: Tetanus is caused by the bacterium Clostridium tetani. Metachromatic granules are not a typical feature of Clostridium species.

Answer: Robertson cooked-meat medium

Robertson cooked-meat medium is an example of an anaerobic medium. It is specifically designed to provide an oxygen-free environment for the growth of anaerobic bacteria. This medium contains chopped meat, which helps to remove any remaining oxygen and create suitable conditions for anaerobes.

The other options are incorrect:

• Nutrient agar: This is a general-purpose medium that can support the growth of a wide variety of bacteria, including both aerobes and anaerobes. It does not specifically create an anaerobic environment, and therefore, it is not considered an anaerobic medium.
• Selenite F broth: This is an enrichment medium used for the isolation of Salmonella bacteria. It contains a high concentration of selenite, which inhibits the growth of other competing bacteria but allows Salmonella to survive and grow. While it can be used for the initial enrichment of anaerobes, it does not provide a long-term anaerobic environment for their growth.
• MacConkey agar: This is a differential medium used to distinguish between lactose-fermenting and non-lactose-fermenting bacteria. It does not provide an anaerobic environment and is not suitable for the growth of strict anaerobes.

Answer: Scabies

Scabies is not a waterborne disease. It is a parasitic infestation of the skin caused by the Sarcoptes scabiei mite. The mite burrows into the skin, leading to itching and skin irritation. Unlike the other options, scabies is not transmitted through contaminated water.

The other options are incorrect:

• Cholera: Cholera is a waterborne disease caused by the bacterium Vibrio cholerae. It is typically transmitted through the ingestion of contaminated water or food.
• Giardiasis: Giardiasis is a waterborne disease caused by the protozoan parasite Giardia lamblia. It is commonly transmitted through the ingestion of water contaminated with the cysts of the parasite.
• Salmonellosis: Salmonellosis is a bacterial infection caused by various strains of Salmonella bacteria. It can be transmitted through the consumption of contaminated water or food, especially products of animal origin.

Answer: Endemic

The existence of Tuberculosis in the population of Faisalabad is an example of an endemic condition. Endemic refers to the constant presence or usual prevalence of a disease within a specific geographic area or population. In this case, Tuberculosis is consistently present in the population of Faisalabad.

The other options are incorrect:

• Epidemic: An epidemic refers to the occurrence of a disease in a community or region in excess of what is normally expected. It is often characterized by a sudden and widespread outbreak of the disease.
• Pandemic: A pandemic refers to a global outbreak of a disease that affects people across multiple countries or continents. It involves the spread of the disease on a larger scale than an epidemic.
• Sporadic: Sporadic refers to the occurrence of isolated cases or scattered instances of a disease within a population. It does not imply a consistent or regular presence of the disease.

Answer: Fungi

Mycotoxins are toxic compounds produced by certain fungi. These fungi may contaminate food crops, especially under conditions of high humidity and improper storage. Mycotoxins pose a risk to human and animal health when contaminated food products are consumed.

The other options are incorrect:

• Bacteria: Bacteria do not produce mycotoxins. Mycotoxins are specifically associated with certain species of fungi and their metabolic byproducts.
• Viruses: Viruses do not produce mycotoxins. Mycotoxins are substances associated with fungal metabolism and are not produced by viral organisms.
• Protozoa: Protozoa, which are single-celled eukaryotic organisms, do not produce mycotoxins. Mycotoxins are primarily associated with the fungal kingdom.

Answer: 72°C

In the polymerase chain reaction (PCR), the extension step is typically done at a temperature of 72 °C. During the extension step, the DNA polymerase enzyme synthesizes a complementary strand of DNA by adding nucleotides to the 3′ end of the primers. The extension temperature of 72 °C is optimal for the activity of the DNA polymerase enzyme commonly used in PCR reactions, such as Taq polymerase.

The other options are incorrect:

• 50-60°C: This temperature range is commonly associated with the annealing step in PCR, where primers bind to the complementary sequences on the target DNA.
• 95°C: 95°C is the temperature used during the denaturation step in PCR. At this temperature, the DNA template is denatured, separating the two strands.
• 37°C: 37°C is often used as a temperature for incubation in some molecular biology techniques, but it is not the temperature for the extension step in PCR.

Answer: IgE

Basophils have receptors for IgE antibodies. IgE antibodies play a crucial role in allergic responses. When an individual is exposed to an allergen, IgE antibodies bind to the surface of basophils and mast cells. Upon subsequent exposure to the same allergen, these IgE-bound cells release histamine and other mediators, contributing to allergic reactions.

The other options are incorrect:

• IgG: Basophils do not have specific receptors for IgG antibodies. IgG antibodies are associated with various immune functions, including opsonization and antibody-dependent cellular cytotoxicity.
• IgA: Basophils do not have specific receptors for IgA antibodies. IgA antibodies are primarily found in mucosal secretions and play a role in mucosal immunity.
• IgD: Basophils do not have specific receptors for IgD antibodies. IgD antibodies are found on the surface of B cells and are involved in the activation of the immune response.

Answer: Proteins

LipoproteinsEnzymes are chemically classified as proteins. Enzymes are biological catalysts that facilitate and accelerate chemical reactions in living organisms. They are composed of amino acids, and their three-dimensional structure is critical for their function. Enzymes play a crucial role in various cellular processes, mediating biochemical reactions necessary for life.

The other options are incorrect:

• Lipids: Lipids are a diverse group of organic compounds that include fats, oils, and phospholipids. Enzymes, however, are not chemically classified as lipids.
• Carbohydrates: Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen. Enzymes are not chemically classified as carbohydrates. They are primarily composed of amino acids.
• Lipoproteins: Lipoproteins are complexes of proteins and lipids. Enzymes are not chemically classified as lipoproteins; instead, they are considered proteins.

Answer: Thermophiles

Thermophiles are microorganisms that thrive at high temperatures, and their optimum growth temperature is greater than 45°C. These organisms are adapted to extreme heat environments, such as hot springs and geothermal areas. They have specific molecular and structural adaptations that allow them to function optimally at elevated temperatures.

The other options are incorrect:

• Mesophilic: Mesophiles have an optimum growth temperature in the moderate range, typically between 20°C and 45°C. They are adapted to environments with moderate temperatures, such as the human body.
• Psychrophiles: Psychrophiles are microorganisms that prefer cold temperatures. Their optimum growth temperature is below 20°C, and they are commonly found in cold environments, such as polar regions.
• Psychrophilic: “Psychrophilic” is an adjective describing organisms that are adapted to cold temperatures, similar to psychrophiles. It is not a specific category of microorganisms with an optimum growth temperature greater than 45°C.

Answer: Helicase

The enzyme that unzips and unwinds the DNA during processes like DNA replication is called helicase. Helicase is responsible for breaking the hydrogen bonds between complementary bases of the DNA strands, allowing the strands to separate and providing access to the DNA template for various enzymatic processes.

The other options are incorrect:

• DNA polymerase: DNA polymerase is an enzyme involved in DNA replication, but its primary function is to synthesize a new complementary strand of DNA based on the existing template strand. It does not unzip or unwind the DNA.
• Primase: Primase is an enzyme that synthesizes short RNA primers on the DNA template, providing a starting point for DNA synthesis by DNA polymerase. It is not directly involved in unzipping or unwinding the DNA.
• Reverse transcriptase: Reverse transcriptase is an enzyme involved in the synthesis of DNA from an RNA template, as observed in retroviruses. It is not typically associated with the unzipping or unwinding of DNA.

Answer: Urease

Helicobacter pylori possesses urease, an enzyme that helps to neutralize stomach acid (HCl) by catalyzing the hydrolysis of urea to produce ammonia and carbon dioxide. The ammonia produced in this process can neutralize the acidic environment around the bacterium, allowing it to survive in the stomach’s harsh conditions.

The other options are incorrect:

• Coagulase: Coagulase is an enzyme produced by some bacteria, particularly Staphylococcus aureus, and is involved in the coagulation of blood plasma proteins. It is not related to neutralizing stomach acid.
• Hyaluronidase: Hyaluronidase is an enzyme that hydrolyzes hyaluronic acid, a component of connective tissue. It is not involved in neutralizing stomach acid and is not a characteristic enzyme of Helicobacter pylori.
• Catalase: Catalase is an enzyme that catalyzes the breakdown of hydrogen peroxide into water and oxygen. It is not directly involved in neutralizing stomach acid and is not a characteristic enzyme of Helicobacter pylori in the context of acid neutralization.

Answer: Excess CO²

Capnophiles are bacteria that grow best in an environment with a high concentration of carbon dioxide (CO²), typically exceeding 5%. The excess CO² helps them with various metabolic processes and creates a more favorable environment for their growth.

The other options are incorrect:

• Small percentage of CO²: Capnophiles typically require a much higher CO² concentration than the normal atmospheric level (0.04%) for optimal growth.
• Excess of O²: Most capnophiles are microaerophilic, meaning they require a small amount of oxygen for respiration. Excess oxygen can be harmful to them.
• Absence of O²: Capnophiles are not obligate anaerobes and require some oxygen for survival. They cannot grow in the complete absence of oxygen.

Answer: Unbroken skin

The first line of defense in the body is the physical and chemical barrier provided by unbroken skin. Intact skin serves as a protective barrier that prevents the entry of pathogens into the body. The skin, along with mucous membranes, forms the body’s primary defense against external microorganisms.

The other options are incorrect:

• Antibody molecules: Antibody molecules are part of the immune response and constitute the second line of defense. Antibodies are produced in response to the recognition of antigens and are involved in specific immune reactions.
• Antigen molecules: Antigen molecules are substances that can trigger an immune response. While antigens are important for immune recognition, they are not the first line of defense. The physical barrier of unbroken skin is the initial protective measure.
• Phagocytic cells: Phagocytic cells, such as macrophages and neutrophils, are components of the immune system that engulf and digest pathogens. They are part of the second line of defense, responding after the initial physical and chemical barriers.

Answer: Staphylococcus aureus

Toxic shock syndrome (TSS) is caused by the toxin produced by Staphylococcus aureus, particularly the strain known for producing the toxic shock syndrome toxin-1 (TSST-1). TSS is a rare but potentially severe condition characterized by fever, rash, low blood pressure, and multi-organ dysfunction.

The other options are incorrect:

• Streptococcus pyogenes: Streptococcus pyogenes is associated with various infections, but it is not the causative agent of toxic shock syndrome. TSS is specifically linked to the toxin produced by Staphylococcus aureus.
• Vibrio cholerae: Vibrio cholerae is the bacterium responsible for causing cholera, a disease characterized by severe diarrhea and dehydration. It is not associated with toxic shock syndrome.
• Proteus vulgaris: Proteus vulgaris is a bacterium that can be found in various environments, including the human gastrointestinal tract. It is not known for causing toxic shock syndrome.

Answer: Isopropanol

Isopropanol is commonly used to precipitate DNA during DNA extraction. When isopropanol is added to a DNA solution, it induces the precipitation of DNA strands. The precipitated DNA can then be collected by centrifugation, washed, and further processed for various molecular biology applications.

The other options are incorrect:

• SDS (Sodium Dodecyl Sulfate): SDS is a detergent often used in DNA extraction procedures, but it is not used specifically for DNA precipitation. SDS is commonly used to break down cell membranes and denature proteins.
• Phenol: Phenol is used in DNA extraction for DNA purification and removal of proteins, but it is not used for DNA precipitation. Phenol is more commonly associated with DNA extraction procedures involving phenol-chloroform extraction.
• EDTA (Ethylenediaminetetraacetic acid): EDTA is a chelating agent often used in DNA extraction to sequester divalent metal ions. It is not used for DNA precipitation but helps prevent the degradation of DNA by metal-dependent nucleases.

Answer: Hospitals

Nosocomial infections, also known as healthcare-associated infections (HAIs), are acquired from hospitals or other healthcare facilities. These infections occur as a result of medical interventions, procedures, or contact with healthcare settings. Nosocomial infections can be caused by various microorganisms and may affect patients, healthcare workers, or visitors.

The other options are incorrect:

• Plants: Nosocomial infections are not acquired from plants. The term “nosocomial” specifically refers to infections associated with healthcare environments.
• Animals: Nosocomial infections are not acquired from animals. The primary source is the healthcare environment, where patients may come into contact with infectious agents during medical care.
• Community: Nosocomial infections are distinct from community-acquired infections. Community-acquired infections are those acquired outside healthcare settings, while nosocomial infections specifically originate within healthcare facilities.

Answer: Measles

The virus family responsible for causing mumps is also associated with measles. Both mumps and measles are caused by viruses belonging to the Paramyxoviridae family. Mumps is caused by the mumps virus, and measles is caused by the measles virus, both of which are enveloped RNA viruses.

The other options are incorrect:

• Hepatitis: Hepatitis is caused by various viruses, including hepatitis A, B, C, D, and E. It is not caused by the virus family associated with mumps.
• Rabies: Rabies is caused by the Rabies lyssavirus, which belongs to the Rhabdoviridae family. It is not caused by the same virus family as mumps.
• Smallpox: Smallpox is caused by the variola virus, a member of the Poxviridae family. It is not caused by the virus family associated with mumps.

Answer: Malignant tumors of skin or mucus membrane

Carcinoma refers to malignant tumors that arise from epithelial tissues, including the skin and mucous membranes. Epithelial tissues cover the body surfaces, line organs, and form glands. Carcinomas are the most common type of cancer and can occur in various organs, such as the skin, lungs, colon, and other tissues derived from epithelial cells.

The other options are incorrect:

• Malignant tumors of the connective tissue: Malignant tumors of the connective tissue are referred to as sarcomas, not carcinomas. Sarcomas arise from tissues such as bone, muscle, or cartilage.
• Malignant tumors of the colon: Malignant tumors of the colon are specifically known as colorectal cancer or adenocarcinoma of the colon. The term “carcinoma” alone does not refer specifically to colon cancer.
• Malignant tumors of the lungs: Malignant tumors of the lungs are often categorized as lung cancer, with the most common type being non-small cell lung carcinoma (NSCLC) or small cell lung carcinoma (SCLC). Carcinoma alone can refer to lung cancer, but it is a broad term encompassing various epithelial malignancies.

Answer: Closed system

Batch fermentation is also called a closed system. In batch fermentation, a specific quantity of nutrient medium is inoculated with microorganisms, and the entire content is incubated without the addition of fresh medium or removal of spent medium during the process. The fermentation occurs in a closed vessel, and the system is not continuously fed or emptied during the fermentation process.

The other options are incorrect:

• Open system: An open system involves continuous exchange of nutrients and waste products with the external environment. In batch fermentation, the system is closed, and there is no continuous exchange during the fermentation process.
• Sub-merger system: “Sub-merger system” is not a commonly used term in the context of fermentation. The correct term for a system where microorganisms are submerged in a liquid medium is “submerged system” or “submerged fermentation.”
• Continuous system: Continuous fermentation involves a continuous flow of fresh medium into the fermentation vessel and the removal of spent medium, providing a continuous supply of nutrients and removal of products. Batch fermentation, on the other hand, is a closed system without continuous feeding or removal.

Answer: In dark field microscope

111

Live bacterial cells can be examined using a dark field microscope. In dark field microscopy, the specimen is illuminated with light that does not directly enter the objective lens, creating a dark background. This allows observation of live and unstained bacterial cells, enhancing their visibility without the need for staining.

The other options are incorrect:

• After Gram staining: Gram staining is a technique used to differentiate bacterial cells based on their cell wall characteristics. It involves the use of different stains and is typically applied to fixed bacterial cells. It is not suitable for observing live bacterial cells.
• After special staining: Special staining techniques, such as acid-fast staining or spore staining, are often applied to fixed and stained bacterial cells to highlight specific structures or characteristics. These techniques are not primarily used for observing live cells.
• Acid-fast staining: Acid-fast staining is a specific staining technique used to identify acid-fast bacteria, such as Mycobacterium species. It is not typically applied to live bacterial cells but to fixed and stained specimens.

Answer: Pentamer

IgM antibodies exist in a pentameric structure. IgM is the first antibody class produced during an immune response and is composed of five monomeric subunits connected by a J chain. This pentameric structure contributes to its effective role in agglutination and complement activation.

The other options are incorrect:

• Monomer: IgM antibodies are not monomers. Monomers refer to single units of a protein. IgM is a polymer composed of multiple monomeric subunits.
• Dimer: IgM antibodies are not dimers. Dimers consist of two subunits, while IgM is a larger pentameric structure.
• Trimer: IgM antibodies are not trimers. Trimers consist of three subunits, whereas IgM has a pentameric structure with five subunits.

Answer: 5′ AGGCCT 3’

A palindrome is a sequence of nucleotides or amino acids that reads the same forward and backward on complementary strands. The sequence “5′ AGGCCT 3’” is a palindrome because its reverse complement is the same as the original sequence (“3′ TCCGGT 5’”).

The other options are incorrect:

• 5′-GATTA-3′: This sequence is not a palindrome. Its reverse complement is “3′-AATCT-5′,” which is not the same as the original sequence.
• 5′-GACTTT-3′: This sequence is not a palindrome. Its reverse complement is “3′-CTGAAA-5′,” which is not the same as the original sequence.
• 5′-GACCAA-3′: This sequence is not a palindrome. Its reverse complement is “3′-CTGGTT-5′,” which is not the same as the original sequence.

Answer: Log phase

Bacterial cells are at their metabolic peak during the log phase (also known as the exponential phase). In the log phase, bacteria experience rapid and exponential growth. During this phase, the rate of cell division is maximal, and the population size increases rapidly. Metabolism is highly active as bacteria utilize nutrients for energy and cellular processes.

The other options are incorrect:

• Lag phase: The lag phase is characterized by a period of adjustment where bacteria adapt to their new environment. Metabolic activity is low during this phase as cells prepare for active growth.
• Stationary phase: The stationary phase follows the log phase and is characterized by a stabilization of the population size due to resource limitations. Metabolic activity decreases, and cell division is balanced by cell death.
• Decline phase: The decline phase occurs when the environmental conditions are no longer suitable for bacterial growth. During this phase, the population size decreases, and metabolic activity declines as cells may die or become dormant.

Answer: Penicillin

Penicillin is an antibiotic that primarily acts on bacterial cell walls. It inhibits the synthesis of peptidoglycan, a crucial component of the bacterial cell wall. By interfering with cell wall formation, penicillin weakens the cell wall structure, leading to cell lysis and death. Penicillin is effective against a wide range of bacteria, especially those that are actively growing and dividing.

The other options are incorrect:

• Chloramphenicol: Chloramphenicol inhibits bacterial protein synthesis by binding to the bacterial ribosome. It does not directly target the cell wall.
• Rifampin: Rifampin acts on bacterial RNA polymerase, inhibiting the transcription of RNA. It is not primarily involved in disrupting bacterial cell walls.
• Polymyxins: Polymyxins disrupt bacterial cell membranes. They interact with lipopolysaccharides in the outer membrane of Gram-negative bacteria, leading to membrane damage. Polymyxins do not directly target cell walls.

Answer: Proteus vulgaris

Proteus vulgaris is a motile bacterium. Motility in bacteria often involves the presence of flagella, which are whip-like structures that enable movement. Proteus vulgaris is known for its characteristic swarming motility on solid agar surfaces, displaying a rapid and coordinated movement.

The other options are incorrect:

• Klebsiella pneumoniae: Klebsiella pneumoniae is typically non-motile. It lacks flagella and is not known for active movement.
• Bacillus anthracis: Bacillus anthracis is generally non-motile. Although some species of Bacillus are motile, Bacillus anthracis lacks flagella.
• Shigella flexneri: Shigella flexneri is non-motile. It is an intracellular pathogen that causes bacillary dysentery, and its movement within the host is not reliant on flagellar motility.

Answer: Chemotaxis

Chemotaxis refers to the migration of leukocytes (white blood cells) in response to specific chemicals or signals, guiding them toward the site of injury or infection. These chemicals, known as chemoattractants, help direct the movement of leukocytes to areas where their presence is needed for immune responses.

The other options are incorrect:

• Specific immunity: Specific immunity, also known as adaptive or acquired immunity, involves the specific recognition and targeting of pathogens by immune cells. It is characterized by the actions of antibodies and lymphocytes and is not specifically related to the directed movement of leukocytes toward a site of injury.
• Phagocytosis: Phagocytosis is the process by which cells, including leukocytes, engulf and digest foreign particles, such as bacteria. While phagocytosis is part of the immune response, it does not specifically refer to the directed movement of leukocytes in response to chemical signals.
• Inflammation: Inflammation is a complex biological response to injury or infection, involving various processes, including vasodilation, increased permeability, and recruitment of immune cells. Chemotaxis is a specific aspect of the inflammatory response that directs leukocytes toward the site of injury or infection.

Answer: Female Aedes

Female Aedes mosquitoes serve as vectors to transmit the Dengue virus to humans. The Aedes mosquitoes, particularly Aedes aegypti and Aedes albopictus, are known vectors for various arboviruses, including the Dengue virus. Only female mosquitoes feed on blood, and during this blood-feeding process, they can acquire and subsequently transmit the Dengue virus to humans.

The other options are incorrect:

• Male Culex: Male mosquitoes, including male Culex mosquitoes, do not feed on blood. They primarily feed on plant nectar and do not play a role in the transmission of Dengue virus.
• Male Aedes: Similar to male Culex mosquitoes, male Aedes mosquitoes do not feed on blood. They primarily feed on plant nectar and are not involved in the transmission of Dengue virus.
• Female Culex: While female Culex mosquitoes can serve as vectors for other diseases such as West Nile virus, they are not typically associated with the transmission of the Dengue virus.

Answer: Microaerophilic

Microaerophilic organisms are those that grow best in environments with a low concentration of oxygen, typically lower than atmospheric levels. They require oxygen for growth but thrive in conditions where the oxygen concentration is lower than what is present in the atmosphere.

The other options are incorrect:

• Anaerobic: Anaerobic organisms do not require oxygen for growth and can grow in the absence of oxygen. They can be harmed or inhibited by the presence of oxygen.
• Facultative anaerobic: Facultative anaerobic organisms can grow in the presence or absence of oxygen. They are adaptable and can switch between aerobic and anaerobic metabolism based on the availability of oxygen.
• Obligate aerobes: Obligate aerobes require oxygen for their growth and survival. They cannot grow in the absence of oxygen and may be harmed by anaerobic conditions.

Answer: Neutrophils

Neutrophils primarily function as phagocytic cells. They are a type of white blood cell (leukocyte) and are essential components of the immune system. Neutrophils are highly effective at engulfing and digesting bacteria, fungi, and other foreign particles through a process called phagocytosis. They play a crucial role in the innate immune response.

The other options are incorrect:

• B-lymphocytes: B-lymphocytes are a type of white blood cell involved in adaptive immunity. They are responsible for producing antibodies and are not primarily phagocytic cells.
• T-lymphocytes: T-lymphocytes, or T cells, are also part of adaptive immunity. They play a central role in cell-mediated immunity and are not primarily involved in phagocytosis.
• Eosinophils: Eosinophils are white blood cells that are involved in the immune response against parasitic infections and allergies. While they have some phagocytic activity, it is not their primary function.

Answer: All of these

Acquired immunity is a broad term encompassing both natural and artificial immunity, as well as active and passive immunity. Here’s a breakdown:

• Natural immunity: This is acquired through exposure to pathogens, either by directly contracting a disease or through contact with weakened or inactive forms of the pathogen. This exposure triggers the immune system to develop antibodies and other immune cells specific to that pathogen, providing protection against future infections.
• Artificial immunity: This is acquired through vaccination. Vaccines contain weakened or inactive forms of pathogens or their components, which stimulate the immune system to develop immunity without causing the actual disease.
• Active immunity: This is acquired when the individual’s immune system actively responds to an antigen (a foreign substance), either through natural exposure or vaccination. This leads to the production of antibodies and other immune cells specific to that antigen, providing long-term protection.

Answer: Nitrification

The formation of nitrate from ammonia is called “nitrification.” Nitrification is a two-step biological oxidation process carried out by specific groups of bacteria. In the first step, ammonia (NH3) is oxidized to nitrite (NO2-) by ammonia-oxidizing bacteria. In the second step, nitrite is further oxidized to nitrate (NO3-) by nitrite-oxidizing bacteria. Both of these processes contribute to the nitrogen cycle in soil and aquatic environments.

The other options are incorrect:

• Ammonification: Ammonification is the process by which organic nitrogen, such as proteins and amino acids, is converted into ammonia or ammonium ions. It is a step in the decomposition of organic matter.
• Denitrification: Denitrification is the process by which nitrate (NO3-) is reduced to nitrogen gas (N2) or other nitrogen oxides. It is a microbial process that returns nitrogen to the atmosphere.
• Nitrogen fixation: Nitrogen fixation is the conversion of atmospheric nitrogen (N2) into ammonia or related compounds. This process is carried out by nitrogen-fixing bacteria and is essential for making nitrogen available to plants.

Answer: Presynaptic terminal of spinal cord

The main site of action of the tetanus toxin is the presynaptic terminal of the spinal cord. Tetanus toxin, produced by the bacterium Clostridium tetani, acts at the neuromuscular junction. It interferes with the release of inhibitory neurotransmitters, such as gamma-aminobutyric acid (GABA) and glycine, leading to uncontrolled muscle contractions or spasms characteristic of tetanus.

The other options are incorrect:

• Muscle fibers:Tetanus toxin does not directly target muscle fibers. Its primary action occurs at the level of the neuromuscular junction, affecting neurotransmitter release.
• Neuromuscular junction: While the neuromuscular junction is involved, the tetanus toxin specifically acts on the presynaptic terminal of the spinal cord, disrupting the normal regulation of inhibitory neurotransmitters.
• Postsynaptic terminal of spinal cord: The primary site of action of tetanus toxin is the presynaptic terminal of the spinal cord, not the postsynaptic terminal. It interferes with the release of neurotransmitters before the synaptic cleft.

Answer: Transformation

The acquisition of naked DNA by intact bacteria is called “transformation.” In this process, bacteria take up external DNA fragments from their environment and incorporate them into their own genome. This phenomenon is a natural mechanism observed in some bacteria, allowing them to acquire new genetic material, often in the form of plasmids or genomic DNA.

The other options are incorrect:

• Transduction: Transduction involves the transfer of genetic material between bacteria using bacteriophages (viruses that infect bacteria) as vectors. It is not related to the direct uptake of naked DNA from the environment.
• Transcription: Transcription is the process by which genetic information in DNA is used to synthesize RNA. It is a cellular process occurring within the bacterial cell and is not related to the uptake of external DNA.
• Conjugation: Conjugation involves the direct transfer of genetic material (usually plasmids) from one bacterial cell to another through a physical bridge known as a pilus. It is different from transformation, which involves the uptake of free DNA from the environment.

Answer: Ligase

T4 DNA ligase is an enzyme that joins fragments of DNA by catalyzing the formation of phosphodiester bonds between the 3′-hydroxyl group of one nucleotide and the 5′-phosphate group of the next nucleotide. This enzyme is essential for various techniques in molecular biology, such as DNA cloning and gene sequencing.

The other options are incorrect:

• Restriction enzyme: Restriction enzymes are endonucleases that cut DNA at specific sequences. Their function is opposite to the function of ligases.
• Polymerase: Polymerases are enzymes that synthesize new DNA strands by adding nucleotides to a growing chain. While they work with DNA, they do not directly join fragments of DNA.
• Integrase: Integrases are enzymes that insert DNA fragments into specific locations in the genome. Their function is different from ligases, which can join any compatible DNA fragments.

Answer: Fimbriae

Fimbriae are thin, hair-like appendages protruding from the surface of bacterial cells. They play a crucial role in attachment and colonization of surfaces. Fimbriae enable bacteria to adhere to host tissues, surfaces, or other cells, promoting the establishment of infections or biofilms.

The other options are incorrect:

• Sex pilli: Sex pili (or sex fimbriae) are structures involved in bacterial conjugation, a process of horizontal gene transfer between bacterial cells. They are distinct from fimbriae and serve a different function.
• Capsule: Capsules are outer protective layers composed of polysaccharides or proteins. While capsules contribute to bacterial virulence and protection, they are not thin appendages for attachment like fimbriae.
• Cell wall: The bacterial cell wall provides structural support and protection. It is not directly involved in attachment and colonization like fimbriae.

Answer: Sterilization

Sterilization is the process of killing or eliminating all microorganisms, including both vegetative (actively growing) and sporing states. It aims to render an object or environment completely free of viable microbes, ensuring the absence of bacteria, viruses, fungi, and their spores.

The other options are incorrect:

• Disinfection: Disinfection refers to the reduction of microbial populations to a level that is considered safe for public health. It may not eliminate all microbial forms, including spores.
• Pasteurization: Pasteurization is a process of heat treatment used to reduce the number of viable microorganisms in food and beverages, but it does not achieve the complete elimination of all microbial life, including spores.
• Antisepsis: Antisepsis involves the application of antiseptic agents to living tissues to reduce or prevent the growth of microorganisms. It is not the complete elimination of all microorganisms, as seen in sterilization.