A quantitative analysis of Salmonella Typhimurium metabolism during infection

In this thesis, Salmonella metabolism during infection was investigated. The goal was to gain a quantitative and comprehensive understanding of Salmonella in vivo nutrient supply, utilization and growth.
To achieve this goal, we used a combined experimental / in silico approach. First, we generated a reconstruction of Salmonella metabolism ([1], see 2.1). This reconstruction was then combined with in vivo data from experimental mutant phenotypes to build a comprehensive quantitative in vivo model of Salmonella metabolism during infection (unpublished data, see 2.2). The data indicated that Salmonella resided in a quantitatively nutrient poor environment, which limited Salmonella in vivo growth. On the other hand, the in vivo niche of Salmonella was qualitatively rich with at least 45 different metabolites available to Salmonella. We then used the in vivo model of infection to analyze reasons for the preponderance of Salmonella genes with undetectable virulence phenotype (unpublished data, see 2.3). Our data indicated that host supply with diverse nutrients resulted in large-scale inactivity of numerous Salmonella metabolic pathways. This together with extensive metabolic redundancy was the main cause of the massive Salmonella gene dispensability during infection. To verify this hypothesis experimentally, an unbiased method for large scale mutagenesis was developed (unpublished data, see 2.4). Results from 20 Salmonella mutator lines indicate that Salmonella can tolerate at least some 2700 to 3900 mutations, emphasizing again that a vast majority of Salmonella genes are dispensable in a defined environment.