Insertion sequence elements as mediators of strain diversity in Lactobacillus helveticus.

Area of Science:

• Microbiology
• Genomics
• Bacterial Evolution

Background:

• Lactobacillus helveticus is a key bacterium in dairy fermentation, particularly in cheese production.
• Understanding genomic variations is crucial for characterizing bacterial strains and their functions.
• Insertion sequence (IS) elements are mobile genetic elements that can influence gene expression and genome structure.

Purpose of the Study:

• To investigate the association of IS elements with gene truncation in Lactobacillus helveticus.
• To determine the conservation and genomic distribution of specific IS elements in cheese isolates.
• To explore the evolutionary implications of IS element insertions in L. helveticus.

Main Methods:

• Genomic analysis of Lactobacillus helveticus DPC 4571 to identify IS element insertions.
• PCR amplification using gene-specific and IS element-specific primers to assess IS element presence and location.
• Randomly amplified polymorphic DNA (RAPD)-PCR to generate genotypic profiles of bacterial strains.

Main Results:

• IS elements were found to truncate genes involved in cellobiose transport, acetaldehyde dehydrogenase, and diacetyl reductase.
• The presence of two IS elements correlated with genotypic profiles obtained via RAPD-PCR.
• One IS element interrupting the cellobiose transport gene was conserved across all tested L. helveticus strains.

Conclusions:

• IS element insertions contribute to genetic diversity and functional gene disruption in L. helveticus.
• The conservation of a specific IS element insertion suggests a significant, early evolutionary event in the species.
• This conserved insertion may represent a marker for the early divergence of Lactobacillus helveticus.