Microbiology and Immunology MCQs 2026

The transfer of genetic material between bacteria through a bacteriophage vector is known as

1. A Transduction ✓
2. B Transformation ✓
3. C Conjugation ✓
4. D Sporulation ✓

Which of the following is a fungal disease affecting humans

1. A Malaria ✓
2. B Tuberculosis ✓
3. C Cholera ✓
4. D Ringworm (Tinea) ✓

Vaccines work primarily by stimulating the production of

1. A Red blood cells ✓
2. B Platelets ✓
3. C Digestive enzymes ✓
4. D Memory cells and antibodies ✓

Malaria is transmitted to humans through the bite of

1. A Female Anopheles mosquito ✓
2. B Female Aedes mosquito ✓
3. C Tsetse fly ✓
4. D Sandfly ✓

Which of the following microorganisms is used in the fermentation of milk into yogurt

1. A Saccharomyces cerevisiae ✓
2. B Rhizobium leguminosarum ✓
3. C Lactobacillus bulgaricus ✓
4. D Escherichia coli ✓

The direct transfer of DNA between two bacteria through a conjugation tube (pilus) is called

1. A Transduction ✓
2. B Transformation ✓
3. C Conjugation ✓
4. D Binary fission ✓

Which of the following bacteria is capable of fixing atmospheric nitrogen in root nodules of leguminous plants

1. A Escherichia coli ✓
2. B Lactobacillus ✓
3. C Rhizobium ✓
4. D Salmonella ✓

Typhoid fever is caused by

1. A Vibrio cholerae ✓
2. B Salmonella typhi ✓
3. C Mycobacterium tuberculosis ✓
4. D Clostridium tetani ✓

Which type of immunity develops after a person recovers from a disease, having produced their own antibodies

1. A Passive natural immunity ✓
2. B Passive artificial immunity ✓
3. C Active natural immunity ✓
4. D Active artificial immunity ✓

Tetanus, characterized by muscle spasms, is caused by a toxin produced by

1. A Vibrio cholerae ✓
2. B Clostridium tetani ✓
3. C Mycobacterium leprae ✓
4. D Salmonella typhi ✓

Which part of the immune system remembers a previously encountered pathogen, enabling a faster response upon re-exposure

1. A Memory cells ✓
2. B Neutrophils ✓
3. C Basophils ✓
4. D Erythrocytes ✓

Which infectious agent consists solely of protein, with no nucleic acid (DNA or RNA) at all

1. A Prion ✓
2. B Viroid ✓
3. C Bacteriophage ✓
4. D Retrovirus ✓

The first line of defense against pathogens, including physical barriers like skin and mucous membranes, is part of

1. A Acquired immunity ✓
2. B Humoral immunity ✓
3. C Innate immunity ✓
4. D Cell-mediated immunity ✓

Which cells engulf and destroy pathogens through phagocytosis

1. A Macrophages ✓
2. B B lymphocytes ✓
3. C Plasma cells ✓
4. D Red blood cells ✓

Leprosy (Hansen's disease) is caused by

1. A Mycobacterium tuberculosis ✓
2. B Vibrio cholerae ✓
3. C Clostridium tetani ✓
4. D Mycobacterium leprae ✓

An allergic reaction occurs when the immune system overreacts to a normally harmless substance called

1. A A pathogen ✓
2. B A toxin ✓
3. C An antibody ✓
4. D An allergen ✓

Which group of microorganisms is characterized by being eukaryotic, unicellular or multicellular, and often photosynthetic

1. A Bacteria ✓
2. B Algae ✓
3. C Viruses ✓
4. D Prions ✓

Antibiotic resistance in bacteria primarily arises due to

1. A Loss of a cell wall ✓
2. B Genetic mutations and horizontal gene transfer ✓
3. C Absence of ribosomes ✓
4. D Formation of a nucleus ✓

Which type of white blood cell directly destroys virus-infected or cancerous cells without antibodies

1. A B lymphocytes ✓
2. B Plasma cells ✓
3. C Basophils ✓
4. D Cytotoxic T lymphocytes (CD8+) ✓

Endospores, which allow certain bacteria to survive harsh conditions, are commonly formed by genera such as

1. A Escherichia and Salmonella ✓
2. B Bacillus and Clostridium ✓
3. C Vibrio and Rhizobium ✓
4. D Mycobacterium and Treponema ✓

The protein coat that encloses the genetic material of a virus is called the

1. A Envelope ✓
2. B Capsid ✓
3. C Capsule ✓
4. D Cell wall ✓

Which of the following diseases can be prevented by the oral polio vaccine (OPV)

1. A Measles ✓
2. B Poliomyelitis ✓
3. C Mumps ✓
4. D Rubella ✓

Retroviruses, such as HIV, are unique because they use the enzyme

1. A DNA polymerase to replicate DNA directly ✓
2. B RNA polymerase to transcribe DNA ✓
3. C Reverse transcriptase to convert RNA into DNA ✓
4. D Ligase to join RNA fragments ✓

Cell-mediated immunity, as opposed to humoral immunity, primarily involves the action of

1. A T lymphocytes ✓
2. B Plasma cells ✓
3. C Antibodies circulating in blood ✓
4. D Mast cells ✓

The first person to observe and describe microorganisms (animalcules) under a microscope was

1. A Robert Hooke ✓
2. B Antonie van Leeuwenhoek ✓
3. C Louis Pasteur ✓
4. D Robert Koch ✓

Which of the following microbial diseases is caused by a protozoan, not a bacterium or virus

1. A Tuberculosis ✓
2. B Tetanus ✓
3. C Malaria ✓
4. D Cholera ✓

Which type of hypersensitivity reaction is responsible for anaphylaxis, a severe and rapid allergic reaction

1. A Type I (immediate) hypersensitivity ✓
2. B Type II hypersensitivity ✓
3. C Type III hypersensitivity ✓
4. D Type IV (delayed) hypersensitivity ✓

Robert Koch is best known for formulating

1. A The theory of evolution ✓
2. B The postulates that establish a causal link between a microbe and a disease ✓
3. C The germ theory of pasteurization ✓
4. D The structure of DNA ✓

Which scientist developed the germ theory of disease and pioneered pasteurization

1. A Louis Pasteur ✓
2. B Robert Koch ✓
3. C Alexander Fleming ✓
4. D Antonie van Leeuwenhoek ✓

A vaccine containing a weakened but live form of a pathogen is called a/an

1. A Inactivated vaccine ✓
2. B Toxoid vaccine ✓
3. C Subunit vaccine ✓
4. D Attenuated (live) vaccine ✓

Which of the following best distinguishes gram-positive from gram-negative bacteria under Gram staining

1. A Gram-positive bacteria retain the crystal violet stain and appear purple ✓
2. B Gram-negative bacteria retain the crystal violet stain and appear purple ✓
3. C Gram-positive bacteria lack a cell wall entirely ✓
4. D Gram-negative bacteria have a thicker peptidoglycan layer ✓

The lymphatic organ that filters blood and recycles old red blood cells is the

1. A Thymus ✓
2. B Tonsils ✓
3. C Spleen ✓
4. D Appendix ✓

Which of the following is an example of an autoimmune disease

1. A Malaria ✓
2. B Tuberculosis ✓
3. C Cholera ✓
4. D Rheumatoid arthritis ✓

Autoimmune diseases occur when the immune system

1. A Mistakenly attacks the body's own healthy cells ✓
2. B Fails to recognize any pathogens at all ✓
3. C Produces excess red blood cells ✓
4. D Cannot produce any antibodies ✓

Interferons are proteins released by virus-infected cells that primarily function to

1. A Directly kill the virus particles ✓
2. B Digest bacterial cell walls ✓
3. C Produce antibodies against the virus ✓
4. D Warn neighboring cells and inhibit viral replication ✓

A molecule on the surface of a pathogen that triggers a specific immune response is called a/an

1. A Antibody ✓
2. B Interferon ✓
3. C Antigen ✓
4. D Cytokine ✓

The complement system in immunity refers to

1. A A group of hormones regulating blood sugar ✓
2. B Antibodies produced by plasma cells ✓
3. C A group of blood proteins that enhance the ability to clear pathogens ✓
4. D White blood cells that engulf bacteria ✓

Saccharomyces cerevisiae, commonly known as baker's and brewer's yeast, is used industrially to produce

1. A Ethanol and carbon dioxide through fermentation ✓
2. B Antibiotics such as penicillin ✓
3. C Insulin through recombinant DNA ✓
4. D Nitrogen fixation in soil ✓

The gram staining technique differentiates bacteria based on differences in

1. A Size of bacterial cell ✓
2. B Presence of flagella ✓
3. C Shape of the bacterium ✓
4. D Composition of the cell wall ✓

Which scientist is credited with discovering penicillin, the first antibiotic

1. A Robert Koch ✓
2. B Louis Pasteur ✓
3. C Edward Jenner ✓
4. D Alexander Fleming ✓

The lytic and lysogenic cycles describe the reproduction strategies of

1. A Bacteria ✓
2. B Fungi ✓
3. C Bacteriophages (viruses) ✓
4. D Protozoa ✓

Which type of immunity is provided by antibodies transferred from mother to fetus through the placenta

1. A Active natural immunity ✓
2. B Passive natural immunity ✓
3. C Active artificial immunity ✓
4. D Passive artificial immunity ✓

Tuberculosis is caused by

1. A Vibrio cholerae ✓
2. B Mycobacterium tuberculosis ✓
3. C Salmonella typhi ✓
4. D Clostridium tetani ✓

The process by which bacteria take up free DNA fragments from their surroundings is called

1. A Transformation ✓
2. B Conjugation ✓
3. C Transduction ✓
4. D Binary fission ✓

Which blood cells are primarily responsible for antibody-mediated (humoral) immunity

1. A T lymphocytes ✓
2. B B lymphocytes ✓
3. C Neutrophils ✓
4. D Monocytes ✓

HIV primarily attacks which type of cell in the human immune system

1. A B lymphocytes ✓
2. B Helper T lymphocytes (CD4+) ✓
3. C Red blood cells ✓
4. D Platelets ✓

Edward Jenner is best known for developing the first vaccine against

1. A Rabies ✓
2. B Anthrax ✓
3. C Polio ✓
4. D Smallpox ✓

Which of the following best describes the structure of a typical antibody molecule

1. A Single straight polypeptide chain ✓
2. B Circular plasmid-like structure ✓
3. C Y-shaped molecule with two heavy and two light chains ✓
4. D Spherical protein capsid ✓

Which organ is responsible for the maturation of T lymphocytes

1. A Thymus ✓
2. B Spleen ✓
3. C Liver ✓
4. D Bone marrow ✓

Cholera, characterized by severe watery diarrhea, is caused by

1. A Salmonella typhi ✓
2. B Escherichia coli ✓
3. C Mycobacterium leprae ✓
4. D Vibrio cholerae ✓