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Transforming Streptococcus thermophilus with genomic DNA from Streptococcus salivarius

Lamy, Toine
(2024)

Files

Lamy_23231800_2024.pdf
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Details

Supervisors
Patrice Soumillion ; Pierre Morsomme
Faculty
Faculté des bioingénieurs
Degree label
Master [120] : bioingénieur en chimie et bioindustries, à finalité spécialisée
Abstract
Streptococcus thermophilus (Sth) is a lactic acid bacterium widely used in the food industry, particularly in dairy fermentation, and is recognized as Generally Recognized As Safe (GRAS). Due to its stable environment in milk, Sth has undergone genetic regression, losing the ability to ferment certain sugars despite possessing relevant genes as pseudogenes. This study aims to explore the potential of transforming Sth with genomic DNA from Streptococcus salivarius (Ssa), a related species capable of metabolizing a diverse range of carbohydrates. The project involved confirming phenotypes of Sth LMD-9 and Ssa HSISS4, transforming Sth with Ssa DNA, and evaluating the efficiency of this transformation. The genomes of successful transformants were characterized using PCR, Sanger sequencing. Transformations led to isolates capable of metabolizing galactose, trehalose, or maltose. Galactose metabolism was the most frequently acquired capability, though only one Gal+ clone one five integrated Ssa sequences. For trehalose metabolism, homologous recombination likely occurred in clones, as evidenced by identical regions to Ssa. No successful gene amplification was achieved for maltose metabolism. Wholegenome sequencing results are pending, which will further elucidate the genetic changes.