Isotopologue Profiling of Legionella pneumophila

Abstract

Legionella pneumophila (Lp) is commonly found in freshwa-13 C]glucose showed that the carbohydrate is also used as a substrate to feed the central metabolism. The specific labeling patterns due to [1,2-13 C 2 ]glucose identified the Entner-Doudoroff pathway as the predominant route for glucose utilization. In line with these observations, a mutant lacking glucose-6-phosphate dehydrogenase (⌬zwf) did not incorporate label from glucose at significant levels and was slowly outcompeted by the wild type strain in successive rounds of infection in Acanthamoeba castellanii, indicating the importance of this enzyme and of carbohydrate usage in general for the life cycle of Lp.

Importance of Branched-Chain Amino Acid Utilization in Francisella Intracellular Adaptation

“…Furthermore, the systematic prediction of biosynthetic pathways commonly lost during the specialization toward pathogenesis revealed that many pathogens lost the capacity to biosynthesize several amino acids, consistent with the notion that pathogenic species obtain such nutrients from the host. For example, L. pneumophila is auxotrophic for several amino acids (including Cys, Met, Arg, Thr, Val, Ile, Leu, Phe, and Tyr) (18,48) and thus absolutely depends on efficient strategies to acquire them from the host. Remarkably, although Mycobacterium tuberculosis is prototrophic for all 20 amino acids, it still relies on two membrane transporters to capture aspartate and asparagine to exploit these amino acids as a nitrogen source during infection (19,20).…”

Selective Requirement of the Shikimate Pathway of Legionella pneumophila for Intravacuolar Growth within Human Macrophages but Not within Acanthamoeba

“…Although L. pneumophila triggers elevation of the cellular levels of amino acids (31) that are imported into the LCV (23,32), very little is known about the role of bacterial amino acid biosynthetic pathways in intravacuolar proliferation. The tryptophan auxotroph of the L. pneumophila Philadelphia-1 strain grows at a rate similar to that seen with wild-type (WT) L. pneumophila within human monocytes (36), indicating that the host proteasomal degradation generates sufficient levels of Trp to support intravacuolar bacterial growth.…”

“…Amino acids are the main sources of carbon and energy for intravacuolar proliferation of L. pneumophila (18)(19)(20)(21)(22)(23)(24). However, the basal cellular levels of amino acids are below the threshold needed for proliferation of many intracellular pathogens, including Anaplasma, Francisella, and Legionella spp.…”

“…It has been shown by 13 C labeling that L. pneumophila residing within Acanthamoeba spp. or macrophages imports amino acids from the host cell cytosol into the LCV to be utilized by intravacuolar L. pneumophila (23,32), but the import mechanisms involved remain unknown.…”

“…The growth defect exhibited by the ankB mutant within human monocyte-derived macrophages (hMDM) or amoebae, or in vivo, is totally rescued by supplementation with amino acids (31). Amino acids are the preferred sources of carbon and energy for L. pneumophila, but 7 amino acids (Cys, Met, Arg, Thr, Val, Ileu, and Leu) are essential for the organism (18)(19)(20)(21)(22)(23)(24). It has been shown by 13 C labeling that L. pneumophila residing within Acanthamoeba spp.…”