Genetics and Physiology of Lactic Acid Bacteria

Group leader: Jan Martinussen 

The main objective of the group is to understand the genetics and physiology of Lactic Acid Bacteria in order to predict their behavior in different environmental settings. We want to provide the foundation for intelligent development of starter cultures in the industry and subsequent efficient exploitation in the dairies. Lactic Acid Bacteria are a group of Gram-positive bacteria with a huge impact on the Danish society due to their role as dairy workhorses responsible for billions of kroner in turnover: moreover, they are key organisms in the gut microbiota, contributing to health of the Danish population. Lactococcus lactis is by mass and marked value the most important among the lactic acid bacteria used by the dairy industry. Since this organism has been studied by a substantial number of research groups, it has reached a status as the model organism for fermentative gram-positive microorganisms. 
This research group has a strong foundation in molecular biology and bacterial physiology, and has been working with lactic acid bacteria for more than 25 years. The work has been focused on control and regulation of the nucleotide metabolism, but recently, the study of exopolysaccharide biosynthesis has been included. 
Nucleotide metabolism
Apart from being building blocks for RNA and DNA, purine and pyrimidine nucleotides contribute to virtually all cellular processes either as coenzymes used in the biosynthesis of proteins, phospholipids and polysaccharides, or as energy carriers in most metabolic pathways. They are also exploited as intracellular signaling molecules, having profound impact on cell metabolism. 
Exopolysaccharide (EPS) biosynthesis
Exopolysaccharides are extremely important biomolecules; in dairy products like yoghurt, they provide the texture and rheological properties, whereas in environmental settings like the gastro-intestinal tract, they provide protection against bacteriophages, antibiotics and the immune system. Bacterial exopolysaccharide production depends on the genetic makeup and precursor availability in the bacterial cell. We will unravel the fundamental molecular background for exopolysaccharide production.


Jan Martinussen
DTU Bioengineering
+45 45 25 24 98