BSc Third Year (Sem 5 & 6) Microbiology – Daily Revision MCQ (English Medium)
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Which pair of bacteria is the standard starter culture for yoghurt (curd) production?
Chapter 2: Fermented Foods, Probiotics and Prebiotics
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Answer: B. Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus
These two lactic acid bacteria grow together in milk, ferment lactose to lactic acid and give yoghurt its sourness and texture.In the HTST (high temperature short time) method, milk is pasteurised at:
Chapter 3: Dairy Microbiology
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Answer: D. 71.7 °C (about 72 °C) for 15 seconds
HTST = 71.7 °C for 15 s; 63 °C for 30 min is the holding (LTH) method, 135–140 °C for a few seconds is UHT, and 121 °C for 15 min is autoclaving.Which bacterium fixes nitrogen symbiotically in the root nodules of leguminous plants?
Chapter 4: Soil Microbiology and Biofertilizers
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Answer: A. Rhizobium
Rhizobium forms root nodules on legumes and fixes N₂ there; Azotobacter fixes nitrogen free-living, and Nitrosomonas oxidises ammonia to nitrite.Which organism is the standard indicator of faecal contamination of drinking water?
Chapter 6: Water and Sewage Microbiology
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Answer: C. Escherichia coli
E. coli lives in the human and animal gut, so finding it (coliform test) in water shows faecal pollution and possible pathogens.Industrially, penicillin is produced mainly by fermentation using:
Chapter 7: Industrial Fermentation
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Answer: B. Penicillium chrysogenum
High-yielding strains of P. chrysogenum are used for penicillin; S. griseus makes streptomycin and A. niger is used for citric acid.Which staining method is used to detect Mycobacterium tuberculosis in a sputum smear?
Chapter 11: Bacterial Diseases of Humans
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Answer: A. Ziehl–Neelsen (acid-fast) staining
The waxy mycolic-acid wall of Mycobacterium holds carbol fuchsin even after acid-alcohol, so the bacilli show as red acid-fast rods.HIV mainly infects and destroys which cells of the human immune system?
Chapter 12: Viral Diseases of Humans
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Answer: D. CD4⁺ helper T cells
HIV binds the CD4 receptor on helper T cells; their steady loss weakens immunity and leads to AIDS.Malaria, caused by Plasmodium, is transmitted to humans by the bite of:
Chapter 13: Fungal and Protozoal Diseases of Humans
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Answer: C. The female Anopheles mosquito
The female Anopheles injects sporozoites of Plasmodium while feeding; Aedes spreads dengue and Culex spreads filariasis.Which DNA sequence is recognised and cut by the restriction enzyme EcoRI?
Chapter 14: Genetic Engineering
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Answer: A. GAATTC
EcoRI cuts the palindrome 5′-G↓AATTC-3′ leaving sticky ends; GGATCC is BamHI, AAGCTT is HindIII and CCCGGG is SmaI.The heat-stable DNA polymerase used in PCR (Taq polymerase) is obtained from:
Chapter 15: Molecular Techniques: PCR, Blotting and DNA Sequencing
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Answer: D. Thermus aquaticus
Taq polymerase comes from the hot-spring bacterium Thermus aquaticus, so it survives the ~94 °C denaturation step of every PCR cycle.
BSc Third Year (Sem 5 & 6): MCQ in other subjects
All questions are written by PadhaiNotes in our own words from the common syllabus of Maharashtra universities (NEP). Your own university's syllabus may differ a little.