Growth and Stress Tolerance Comprise Independent Metabolic Strategies Critical for Staphylococcus aureus Infection

Staphylococcus aureus is an important pathogen that leads to high mor-bidity and mortality. Although S. aureus produces many factors important for patho-genesis, few have been validated as playing a role in the pathogenesis of S. aureus pneumonia. To gain a better understanding of the genetic elements required for S. aureus pathogenesis in the airway, we performed an unbiased genome-wide transposon sequencing (Tn-seq) screen in a model of acute murine pneumonia. We identified 136 genes important for bacterial survival during infection, with a high proportion involved in metabolic processes. Phenotyping 80 individual dele-tion mutants through diverse in vitro and in vivo assays demonstrated that me-tabolism is linked to several processes, which include biofilm formation, growth, and resistance to host stressors. We further validated the importance of 23 muta-tions in pneumonia. Multivariate and principal-component analyses identified two key metabolic mechanisms enabling infection in the airway, growth (e.g., the abil-ity to replicate and form biofilms) and resistance to host stresses. As deep valida-tion of these hypotheses, we investigated the role of pyruvate carboxylase, which was important across multiple infection models and confirmed a connection between growth and resistance to host cell killing. Pathogenesis is conventionally understood in terms of the host-pathogen interactions that enable a pathogen to neutralize a host's immune response. We demonstrate with the important bacte-rial pathogen S. aureus that microbial metabolism influences key traits important for in vivo infection, independent from host immunomodulation. IMPORTANCE Staphylococcus aureus is an important bacterial pathogen that causes significant morbidity and mortality, infecting numerous bodily sites, including the re-spiratory tract. To identify the bacterial requirements for lung infection, we con-ducted a genome-wide screen in a mouse model of acute pneumonia. We discov-ered that metabolic genes were overrepresented in those required for lung infection. In contrast to the conventional view of pathogenesis focusing on immuno-modulation, we demonstrate through phenotyping of deletion mutants in several functional assays that replicative ability and tolerance against host defenses form two key metabolic dimensions of bacterial infection. These dimensions are independ-ent for most pathways but are coupled in central carbon metabolism and highlight the critical role of bacterial metabolism in survival against host defenses during infection.

Automated summary

Studying the genetic elements of Staphylococcus aureus in pneumonia revealed that metabolic genes are crucial for lung infection, with growth and resistance to host defenses being key metabolic dimensions. This highlights the critical role of bacterial metabolism in surviving against host defenses during infection.