Salmonella enterica Serovar Typhimurium Mutants Unable To Convert Malate to Pyruvate and Oxaloacetate Are Avirulent and Immunogenic in BALB/c Mice

Abstract

Previously, we showed that the Salmonella enterica serovar Typhimurium SR-11 tricarboxylic acid (TCA) cycle must operate as a complete cycle for full virulence after oral infection of BALB/c mice (M. Tchawa Yimga, M. P. Leatham, J. H. Allen, D. C. Laux, T. Conway, and P. S. Cohen, Infect. Immun. 74:1130-1140, 2006). In the same study, we showed that for full virulence, malate must be converted to both oxaloacetate and pyruvate. Moreover, it was recently demonstrated that blocking conversion of succinyl-coenzyme A to succinate attenuates serovar Typhimurium SR-11 but does not make it avirulent; however, blocking conversion of succinate to fumarate renders it completely avirulent and protective against subsequent oral infection with the virulent serovar Typhimurium SR-11 wild-type strain (R. Mercado-Lubo, E. J. Gauger, M. P. Leatham, T. Conway, and P. S. Cohen, Infect. Immun. 76:1128-1134, 2008). Furthermore, the ability to convert succinate to fumarate appeared to be required only after serovar Typhimurium SR-11 became systemic. In the present study, evidence is presented that serovar Typhimurium SR-11 mutants that cannot convert fumarate to malate or that cannot convert malate to both oxaloacetate and pyruvate are also avirulent and protective in BALB/c mice. These results suggest that in BALB/c mice, the malate that is removed from the TCA cycle in serovar Typhimurium SR-11 for conversion to pyruvate must be replenished by succinate or one of its precursors, e.g., arginine or ornithine, which might be available in mouse phagocytes.

The Pyruvate-Tricarboxylic Acid Cycle Node

“…For instance, deletions in the pyruvate pathway have been shown to alter the SPI1-mediated gene expression and infectivity of the Salmonella enterica serovar typhimurium (79). Furthermore, it has been reported that Salmonella mutants that are unable to convert malate to pyruvate and oxaloacetate are avirulent and immunogenic in BALB/c mice (80) and that an incomplete TCA cycle increases the survival of Salmonella during infection (81). Moreover, in Pseudomonas aeruginosa, mutations in TCA cycle enzymes have been shown to affect the type III secretion system of the pathogen (82), and regulators of Staphylococcus aureus responding to TCA cycle-associated metabolic changes have also been implicated in virulence control (83).…”

Anaerobic Respiration of Escherichia coli in the Mouse Intestine

“…Streptomycin-treated mice have been used since 1954 to overcome the colonization resistance that prevents colonization of conventional animals by experimentally introduced enteric bacteria (7). We have made extensive use of the streptomycin-treated mouse model to study nutritional factors that govern colonization of the mouse large intestine by E. coli and Salmonella enterica serovar Typhimurium (3,8,16,18,30,31,34,35,48,49,51,52). Treatment of mice with streptomycin selectively removes facultatively anaerobic E. coli bacteria, enterococci, streptococci, lactobacilli, and anaerobic lactobacilli and bifidobacteria without changing the overall populations of anaerobes, including Bacteroides and Eubacterium (25).…”

Echinacea purpurea Extract Affects the Immune System, Global Metabolome, and Gut Microbiome in Wistar Rats

“…2-Hydroxybutyrate, the metabolic product of threonine, also was found up-regulated in our results. Ornithine acted as a precursor into the immune response (Mercado-Lubo et al, 2009). Glutamate can stimulate the immune system and aspartate is an incomplete degradation product of glutamate in immune cells (Yoshida et al, 1987).…”