Global Metabolomic Analysis of a Mammalian Host Infected with Bacillus anthracis

Abstract

bWhereas DNA provides the information to design life and proteins provide the materials to construct it, the metabolome can be viewed as the physiology that powers it. As such, metabolomics, the field charged with the study of the dynamic small-molecule fluctuations that occur in response to changing biology, is now being used to study the basis of disease. Here, we describe a comprehensive metabolomic analysis of a systemic bacterial infection using Bacillus anthracis, the etiological agent of anthrax disease, as the model pathogen. An organ and blood analysis identified approximately 400 metabolites, including several key classes of lipids involved in inflammation, as being suppressed by B. anthracis. Metabolite changes were detected as early as 1 day postinfection, well before the onset of disease or the spread of bacteria to organs, which testifies to the sensitivity of this methodology. Functional studies using pharmacologic inhibition of host phospholipases support the idea of a role of these key enzymes and lipid mediators in host survival during anthrax disease. Finally, the results are integrated to provide a comprehensive picture of how B. anthracis alters host physiology. Collectively, the results of this study provide a blueprint for using metabolomics as a platform to identify and study novel host-pathogen interactions that shape the outcome of an infection. Metabolomics, a quickly emerging "omics" field in systems biology, is the global analysis of small molecules in a biological sample (1). Since the 1950s, the central dogma of biological information has been the transition from genes to transcript to protein (2). Only recently has the use of high-throughput systems biology been used to study the products of protein activity, the metabolites. The metabolome represents all endogenous and exogenous low-molecular-mass (Ͻ1-kDa) molecules present in a biological state, providing an instantaneous "snapshot" of the cell's metabolic and physiological activity (3). Applications of global metabolomic analysis fall into three broad categories: (i) disease diagnosis, (ii) biomarker and drug discovery, and (iii) study of metabolic pathways and their perturbations due to external factors (1). The analysis of altered metabolites has the potential for discovery of new biomarkers, thus providing the possibility of earlier intervention and insights into the mechanisms of diseases (4).The diagnosis of a bacterial infection encompasses an assessment of clinical symptoms, positive culture of an organism from tissues or blood, and/or reliance on often expensive, outsourced molecular methods (5). Metabolomics provides a unique perspective on bacterial infections as it is able to comprehensively characterize a vast number of metabolic changes in response to a biological perturbation within the host (2). In addition to the potential for biomarker discovery, the metabolic profiles obtained from this analysis can give insight into the identity and nature of molecules involved in the immune response, detect alterations in ho...

Heme catabolism in the causative agent of anthrax

“…Bacilli were detected, albeit at several orders of magnitude lower levels, in the original source organ, the lungs, with the triple mutant demonstrating the lowest levels of the two mutant strains, possibly owing to the defect of hmoB mutant growth in macrophages noted previously (Figs , E). Wild‐type bacilli were as virulent and demonstrated similar levels of dissemination to previous studies (Nguyen et al , ). Taken together, these data suggest that HmoA and IsdG play overlapping and important roles in bacillus biology during infection of a mammalian host.…”

“…It should be noted that previous work by others showed the absence of IsdG did not affect growth in macrophages (Skaar et al , ). To test this hypothesis, we utilized MH‐S mouse alveolar macrophage‐like cells in an infection model previously described by our group (Nguyen et al , ). In this infection system, spores of bacilli are seeded onto cultured macrophages in the presence of horse serum, which inhibits the extracellular germination of spores.…”

“…This is unlike other IsdG‐like proteins, which show various degrees of virulence attenuation when deleted in staphylococci (Reniere and Skaar, ). To determine the contribution of these genes to anthrax, we infected 10‐week‐old A/J mice with isogenic strains individually lacking hmoA or hmoB using an inhalational model of anthrax (Nguyen et al , ). Surprisingly, neither HmoA‐deficient nor HmoB‐deficient bacilli demonstrated a difference compared to WT in survival or bacilli levels in the heart, kidney, spleen or liver (Fig.…”

2-Hydroxyglutarate Metabolism Is Altered in an in vivo Model of LPS Induced Endotoxemia

“…However, in septic patients, intense metabolic dysfunction occurs; contributing to sepsis pathophysiology and its sequelae of organ failure (Chioléro et al, 1997). In recent years, metabolic profiling has been explored as a novel means to approach diagnosis, prognosis and monitoring of septic patients (Seymour et al, 2013;Su et al, 2014;Nguyen et al, 2015). Administration of the bacterial endotoxin, lipopolysaccharide (LPS, the outer component of gram-negative bacteria), replicates the physiology and metabolic changes seen in sepsis (Kamisoglu et al, 2015).…”

Type III Secretion Effector VopQ of Vibrio parahaemolyticus Modulates Central Carbon Metabolism in Epithelial Cells

“…Metabolomics, as an emerging analytical platform, has been applied to decipher host physiological perturbation and identify altered metabolic pathways during bacterial infections (24,25). In this study, we investigated the dynamics of the metabolic processes of the epithelial cells during V. parahaemolyticus infection and the role of the VopQ effector of T3SS1 in modulating host cell metabolism using capillary electrophoresis-time of flight mass spectrometry (CE-TOF/MS).…”