Calcium regulation of Pseudomonas aeruginosa metabolism.

UNLABELLED: Pseudomonas aeruginosa (Pa), a ubiquitous opportunistic pathogen, is notorious for causing diverse life-threatening infections, including lethal lung infections in patients suffering from cystic fibrosis (CF). Pa's ability to adapt to various environments is largely attributed to its metabolic flexibility and extensive regulatory networks. Understanding the mechanisms driving Pa adaptation during colonization of the airways of CF patients is of critical clinical importance. Previous studies by our group and others have shown that elevated Ca2+, a characteristic feature of CF airways, positively regulates virulence factor production in Pa and triggers its transition to a biofilm mode of growth. To generate further insights into Ca2+-dependent adaptations in this pathogen, we aimed to elucidate the regulatory impact of Ca2+ on its metabolism. To characterize Ca2+-induced metabolic alterations, a global untargeted gas chromatography-mass spectrometry-based metabolomics study was performed for both intracellular and extracellular fractions of mid-log and stationary-phase Pa cultures. The altered metabolites were mapped to specific pathways, and selected transcriptional changes and phenotypic outcomes were assayed. Our findings showed that Ca2+ regulates pathways involved in central carbon metabolism, nucleotide synthesis, the shikimate pathway, and glycogen metabolism in both mid-log- and stationary-phase cells. Furthermore, pathways involved in sequestering iron were induced by Ca2+ during both growth phases. Overall, these results indicate that exposure to elevated Ca2+, as within the CF airways, leads to metabolic adjustments and supports Pa survival in this environment.

IMPORTANCE

Individuals with the genetic disorder, cystic fibrosis (CF), are predisposed to developing chronic, life-threatening Pseudomonas aeruginosa (Pa) infections. Elucidating the mechanisms that mediate the adaptation of Pa to the CF airways is essential for the development of new therapeutics to treat these infections. Previously, we have shown that elevated Ca2+ levels, such as those detected in CF airways, induce the production of multiple virulence factors, contributing to the overall pathogenicity of Pa. Here, we report that Ca2+ regulates Pa metabolism, affecting multiple pathways, including central carbon, nucleotide, and shikimate pathways. These metabolic alterations contribute to significant physiological outcomes, some of which are pertinent to Pa virulence and survival within the host. These findings suggest that Ca2+ can serve as a host factor that plays a significant role in Pa patho-adaptation to CF airways.