Question

Lactococcus lactis ssp. lactis can be differentiated from Lactococcus lactis ssp. cremoris based on

• A. Fermentation of galactose and lactose
• B. Fermentation of galactose and maltose
• C. Arginine hydrolysis and fermentation of galactose
• D. Arginine hydrolysis and fermentation of maltose

Hint:

Lactococcal Subspecies Differentiation:
L. lactis subsp. lactis $\rightarrow$ Arginine Hydrolysis (+), Maltose Fermentation (+), Growth at 40$^\circ\text{C}$ (+).
L. lactis subsp. cremoris $\rightarrow$ Arginine Hydrolysis ($-$), Maltose ($-$), Growth at 40$^\circ\text{C}$ ($-$).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Taxonomic differentiation of dairy lactococcal subspecies: Lactococcus lactis subsp. lactis hydrolyzes arginine (deiminase pathway positive) and ferments maltose/ribose (grows at 40°C and 4% NaCl), whereas subsp. cremoris is negative for these traits.
Key Formula or Approach:
\[ \begin{array}{lcccc} Subspecies \& Arginine Hydrolysis \& Maltose Fermentation \& Growth at 40^\circ\text{C} \& Growth in 4\% NaCl \hline \textit{L. lactis} \text{ ssp. } \textit{lactis} \& \mathbf{+} \& \mathbf{+} \& + \& + \textit{L. lactis} \text{ ssp. } \textit{cremoris} \& \mathbf{-} \& \mathbf{-} \& - \& - \end{array} \]

Step 2: Detailed Explanation:
In starter culture taxonomy and differential physiology of mesophilic lactic streptococci:
- Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris are the primary acid-producing starter strains in cheese and dahi:
1. Arginine Hydrolysis (Arginine Deiminase [ADI] Pathway): Subsp. lactis hydrolyzes L-arginine into citrulline, ornithine, $\text{CO}_2$, and ammonia ($+$, turns medium alkaline); subsp. cremoris cannot hydrolyze arginine ($-$).
2. Maltose (and D-Ribose) Fermentation: Subsp. lactis ferments maltose and ribose ($+$); subsp. cremoris cannot ferment maltose ($-$).
3. Subsp. lactis grows at $40^\circ ext{C}$ and in $4.0\%\text{ NaCl}$; subsp. cremoris fails to grow at $40^\circ ext{C}$ or $4\%\text{ NaCl}$.

Step 3: Final Answer:
Therefore, differentiation is based on Arginine hydrolysis and fermentation of maltose, matching option (D).