Metabolic comparison of lactic acid bacteria; genome-scale model of Streptococcus thermophilus LMG18311.

Pastink, Margreet I Teusink, Bas Hols, Pascal [UCL] Visser, Sanne de Vos, Willem M Hugenholtz, Jeroen

In this report we describe amino acid-metabolism and amino acid-dependency of the dairy bacterium Streptococcus thermophilus LMG18311 and compare that with two other characterized lactic acid bacteria, Lactococcus lactis and Lactobacillus plantarum. Through the construction of a genome-scale metabolic model of S. thermophilus, the metabolic differences between the three bacteria were visualized by direct projection on a metabolic map. The comparative analysis revealed the minimal amino acid auxotrophy (only histidine and methionine or cysteine) of S. thermophilus LMG18311 and the broad variety of volatiles produced from amino acids compared to the other two bacteria. It also revealed the limited number of pyruvate branches, forcing this strain to use the homofermentative metabolism for growth optimization. In addition, some industrially-relevant features could be identified in S. thermophilus such as the unique pathway for acetaldehyde (yoghurt flavour) production and the absence of a complete pentose phosphate pathway.