# DBT JRF 2022 — Question 60

Exam: DBT JRF 2022 · Section: B · Topic: Microbiology › Probiotics & Gut Microbiome · Difficulty: Medium

## Question

A probiotic is a live microorganism that is claimed to confer a health benefit by altering the indigenous microflora of the intestinal tract. Which one of the following bacteria has been used widely in probiotics?

## Options

- **A.** Klebsiella pneumonie
- **B.** Pseudomonas putida
- **C.** Lactobacillus lactis
- **D.** Escherichia coli

## Answer

Option C

## Explanation

Lactobacillus lactis in the GI tract: Lactobacillus lactis is a Gram-positive, lactic acid bacterium widely used in: • Fermented dairy products (yogurt, cheese, buttermilk) • Probiotics In the GI tract: • Colonises the intestinal mucosa and competes with pathogens for adhesion sites and nutrients. • Produces lactic acid → lowers local pH → inhibits growth of pathogenic bacteria. • Produces bacteriocins (e.g., nisin) that kill other bacteria. • Stimulates mucosal immune responses. Health benefits: • Reduces incidence of antibiotic-associated diarrhea • May reduce risk of colorectal cancer • Improves lactose tolerance Answer: Lactobacillus lactis colonises the GI tract beneficially, producing lactic acid to inhibit pathogens.

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