Date of Award


Degree Type


Degree Name

Departmental Honors



First Advisor

Dennis Welker


Lactobacillus helveticus is a species of lactic acid bacteria. These bacteria, which produce lactic acid as a major product of carbohydrate metabolism, are used industrially to produce cheese and other fermented dairy products (Ebringer et al., 2008). Many species of lactic acid bacteria also possess probiotic characteristics and when ingested potentially confer increased immune function, regulate gut microbiota, and improve digestion in the host (Reid, 2008). Genetic studies of these probiotic effects and other characteristics of L. helveticus and related species have been hindered by the lack of stably replicating plasmid vectors. Plasmid vectors for several Lactobacillus species have been constructed, but these are often derived from broad host range plasmids and may not be stably maintained over many generations (Fang et al., 2008; Thompson et al., 2001). In L. helveticus specifically, a small number of attempts have been made at adapting plasmid vectors for use in genetic studies, but as the source plasmids were not native to L. helveticus, they were either unable to replicate extrachromosomally or be maintained over many generations (Hagen et al., 2010; Thompson et al., 2001).