Alternative lactose catabolic pathway in Lactococcus lactis IL1403.

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Genetics

Background:

• Lactococcus lactis is a key bacterium in dairy fermentation.
• Understanding lactose assimilation is vital for optimizing industrial processes.
• Previous knowledge on specific genes governing lactose metabolism in L. lactis IL1403 was limited.

Purpose of the Study:

• To identify genes essential for lactose assimilation in Lactococcus lactis subsp. lactis lactis IL1403.
• To characterize the role of specific genes, such as ccpA and bglS, in lactose metabolism.
• To investigate the enzymatic activity of BglS and its contribution to lactose hydrolysis.

Main Methods:

• Isolation of beta-galactosidase phenotype-negative mutants using negative selection on solid media with lactose and X-Gal.
• Gene disruption techniques to study the function of identified genes (ccpA, bglS, Leloir pathway genes).
• Analysis of phospho-beta-galactosidase activity in gene-disrupted mutants.

Main Results:

• Several genes essential for lactose assimilation were identified, including ccpA, bglS, and Leloir pathway genes.
• Disruption of these genes confirmed their essential role in lactose metabolism.
• BglS was identified as the major enzyme responsible for lactose hydrolysis in L. lactis IL1403, exhibiting both phospho-beta-glucosidase and phospho-beta-galactosidase activity.

Conclusions:

• The study elucidates critical genetic components for lactose assimilation in L. lactis IL1403.
• BglS plays a central role in lactose hydrolysis, independent of strong CcpA control.
• These findings provide valuable insights into the molecular mechanisms of lactose metabolism in lactic acid bacteria.