Question

Which statement is not true in relation to Bifidobacteria?

• A. Bifidobacteria are fastidious in their nutritional requirements and need bifidogenic factors for their growth
• B. Bifidobacteria have a G+C content of 55 to 67%
• C. Bifidobacteria are Gram-positive, catalase-positive, nonmotile, gas-producing bacteria
• D. Bifidobacteria are normal inhabitants of intestinal tract of new borns and infants

Hint:

Remember that Bifidobacteria are anaerobic, catalase-negative, and do not produce gas.
Any statement claiming they are catalase-positive or gas-producing is false.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Bifidobacterium is a genus of beneficial, probiotic bacteria that play a critical role in establishing healthy gut microflora, especially in breast-fed infants.

Step 2: Detailed Explanation:
Let us evaluate each statement to identify the incorrect one:
- Statement (A) states that they are fastidious and require bifidogenic factors.
This is true. They have complex nutritional requirements and their growth is stimulated by prebiotics and specific human milk oligosaccharides (bifidogenic factors).
- Statement (B) states that they have a G+C content of \( 55\% \) to \( 67\% \).
This is true. The genus has a high genomic G+C content characteristic of actinobacteria.
- Statement (D) states that they are normal inhabitants of the infant intestinal tract.
This is true. They are among the very first colonizers of the sterile newborn gut.
- Statement (C) states that they are Gram-positive, catalase-positive, nonmotile, and gas-producing.
This is incorrect. While they are Gram-positive and nonmotile, they are strictly anaerobic, catalase-negative (lacking catalase), and do not produce gas during carbohydrate fermentation (they ferment glucose via the unique fructose-6-phosphate shunt without producing \( \text{CO}_2 \)).
Therefore, statement (C) is the incorrect statement.

Step 3: Final Answer:
The statement that is not true is option 3 (Bifidobacteria are Gram-positive, catalase-positive, nonmotile, gas-producing bacteria).