Microbiology and Immunology MCQs 2026

Which scientist developed the germ theory of disease and pioneered pasteurization

1. ALouis Pasteur✓
2. BRobert Koch✓
3. CAlexander Fleming✓
4. DAntonie van Leeuwenhoek✓

Robert Koch is best known for formulating

1. AThe theory of evolution✓
2. BThe postulates that establish a causal link between a microbe and a disease✓
3. CThe germ theory of pasteurization✓
4. DThe structure of DNA✓

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

1. AType I (immediate) hypersensitivity✓
2. BType II hypersensitivity✓
3. CType III hypersensitivity✓
4. DType IV (delayed) hypersensitivity✓

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

1. ATuberculosis✓
2. BTetanus✓
3. CMalaria✓
4. DCholera✓

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

1. ARobert Hooke✓
2. BAntonie van Leeuwenhoek✓
3. CLouis Pasteur✓
4. DRobert Koch✓

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

1. AT lymphocytes✓
2. BPlasma cells✓
3. CAntibodies circulating in blood✓
4. DMast cells✓

Autoimmune diseases occur when the immune system

1. AMistakenly attacks the body's own healthy cells✓
2. BFails to recognize any pathogens at all✓
3. CProduces excess red blood cells✓
4. DCannot produce any antibodies✓

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

1. ADirectly kill the virus particles✓
2. BDigest bacterial cell walls✓
3. CProduce antibodies against the virus✓
4. DWarn 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. AAntibody✓
2. BInterferon✓
3. CAntigen✓
4. DCytokine✓

The complement system in immunity refers to

1. AA group of hormones regulating blood sugar✓
2. BAntibodies produced by plasma cells✓
3. CA group of blood proteins that enhance the ability to clear pathogens✓
4. DWhite blood cells that engulf bacteria✓

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

1. AEthanol and carbon dioxide through fermentation✓
2. BAntibiotics such as penicillin✓
3. CInsulin through recombinant DNA✓
4. DNitrogen fixation in soil✓

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

1. AMemory cells✓
2. BNeutrophils✓
3. CBasophils✓
4. DErythrocytes✓

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

1. ADNA polymerase to replicate DNA directly✓
2. BRNA polymerase to transcribe DNA✓
3. CReverse transcriptase to convert RNA into DNA✓
4. DLigase to join RNA fragments✓

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

1. AMeasles✓
2. BPoliomyelitis✓
3. CMumps✓
4. DRubella✓

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

1. AEnvelope✓
2. BCapsid✓
3. CCapsule✓
4. DCell wall✓

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

1. AEscherichia and Salmonella✓
2. BBacillus and Clostridium✓
3. CVibrio and Rhizobium✓
4. DMycobacterium and Treponema✓

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

1. AB lymphocytes✓
2. BPlasma cells✓
3. CBasophils✓
4. DCytotoxic T lymphocytes (CD8+)✓

Antibiotic resistance in bacteria primarily arises due to

1. ALoss of a cell wall✓
2. BGenetic mutations and horizontal gene transfer✓
3. CAbsence of ribosomes✓
4. DFormation of a nucleus✓

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

1. ABacteria✓
2. BAlgae✓
3. CViruses✓
4. DPrions✓

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

1. AA pathogen✓
2. BA toxin✓
3. CAn antibody✓
4. DAn allergen✓

Leprosy (Hansen's disease) is caused by

1. AMycobacterium tuberculosis✓
2. BVibrio cholerae✓
3. CClostridium tetani✓
4. DMycobacterium leprae✓

Which cells engulf and destroy pathogens through phagocytosis

1. AMacrophages✓
2. BB lymphocytes✓
3. CPlasma cells✓
4. DRed blood cells✓

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

1. AAcquired immunity✓
2. BHumoral immunity✓
3. CInnate immunity✓
4. DCell-mediated immunity✓

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

1. APrion✓
2. BViroid✓
3. CBacteriophage✓
4. DRetrovirus✓

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

1. AVibrio cholerae✓
2. BClostridium tetani✓
3. CMycobacterium leprae✓
4. DSalmonella typhi✓

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

1. APassive natural immunity✓
2. BPassive artificial immunity✓
3. CActive natural immunity✓
4. DActive artificial immunity✓

Typhoid fever is caused by

1. AVibrio cholerae✓
2. BSalmonella typhi✓
3. CMycobacterium tuberculosis✓
4. DClostridium tetani✓

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

1. AEscherichia coli✓
2. BLactobacillus✓
3. CRhizobium✓
4. DSalmonella✓

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

1. ATransduction✓
2. BTransformation✓
3. CConjugation✓
4. DBinary fission✓

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

1. ASaccharomyces cerevisiae✓
2. BRhizobium leguminosarum✓
3. CLactobacillus bulgaricus✓
4. DEscherichia coli✓

Malaria is transmitted to humans through the bite of

1. AFemale Anopheles mosquito✓
2. BFemale Aedes mosquito✓
3. CTsetse fly✓
4. DSandfly✓

Vaccines work primarily by stimulating the production of

1. ARed blood cells✓
2. BPlatelets✓
3. CDigestive enzymes✓
4. DMemory cells and antibodies✓

Which of the following is a fungal disease affecting humans

1. AMalaria✓
2. BTuberculosis✓
3. CCholera✓
4. DRingworm (Tinea)✓

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

1. ATransduction✓
2. BTransformation✓
3. CConjugation✓
4. DSporulation✓

Cholera, characterized by severe watery diarrhea, is caused by

1. ASalmonella typhi✓
2. BEscherichia coli✓
3. CMycobacterium leprae✓
4. DVibrio cholerae✓

Which organ is responsible for the maturation of T lymphocytes

1. AThymus✓
2. BSpleen✓
3. CLiver✓
4. DBone marrow✓

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

1. ASingle straight polypeptide chain✓
2. BCircular plasmid-like structure✓
3. CY-shaped molecule with two heavy and two light chains✓
4. DSpherical protein capsid✓

Edward Jenner is best known for developing the first vaccine against

1. ARabies✓
2. BAnthrax✓
3. CPolio✓
4. DSmallpox✓

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

1. AB lymphocytes✓
2. BHelper T lymphocytes (CD4+)✓
3. CRed blood cells✓
4. DPlatelets✓

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

1. AT lymphocytes✓
2. BB lymphocytes✓
3. CNeutrophils✓
4. DMonocytes✓

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

1. ATransformation✓
2. BConjugation✓
3. CTransduction✓
4. DBinary fission✓

Tuberculosis is caused by

1. AVibrio cholerae✓
2. BMycobacterium tuberculosis✓
3. CSalmonella typhi✓
4. DClostridium tetani✓

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

1. AActive natural immunity✓
2. BPassive natural immunity✓
3. CActive artificial immunity✓
4. DPassive artificial immunity✓

The lytic and lysogenic cycles describe the reproduction strategies of

1. ABacteria✓
2. BFungi✓
3. CBacteriophages (viruses)✓
4. DProtozoa✓

Which scientist is credited with discovering penicillin, the first antibiotic

1. ARobert Koch✓
2. BLouis Pasteur✓
3. CEdward Jenner✓
4. DAlexander Fleming✓

The gram staining technique differentiates bacteria based on differences in

1. ASize of bacterial cell✓
2. BPresence of flagella✓
3. CShape of the bacterium✓
4. DComposition of the cell wall✓

Which of the following is an example of an autoimmune disease

1. AMalaria✓
2. BTuberculosis✓
3. CCholera✓
4. DRheumatoid arthritis✓

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

1. AThymus✓
2. BTonsils✓
3. CSpleen✓
4. DAppendix✓

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

1. AGram-positive bacteria retain the crystal violet stain and appear purple✓
2. BGram-negative bacteria retain the crystal violet stain and appear purple✓
3. CGram-positive bacteria lack a cell wall entirely✓
4. DGram-negative bacteria have a thicker peptidoglycan layer✓

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

1. AInactivated vaccine✓
2. BToxoid vaccine✓
3. CSubunit vaccine✓
4. DAttenuated (live) vaccine✓