(696e) Data-Driven Discovery of Novel Therapeutic Targets through Metabolic Modeling of Staphylococcus Aureus

Authors: 
Islam, M. M., University of Nebraska-Lincoln
Thomas, V. C., University of Nebraska Medical Center
Saha, R., University of Nebraska
Recent trends have recorded a significant rise in community-associated methicillin-resistant Staphylococcus aureus(CA-MRSA) infections. Additionally, most clinical isolates can develop into recalcitrant multiple-antibiotic-resistant and host immune-tolerant biofilm communities, necessitating novel therapeutic strategies for combating S. aureusinfections. Therefore, there has been a steady interest and focus towards understanding how staphylococcal metabolism relates to antibiotic resistance and pathogenesis. In recent years, whole genome sequencing has accelerated the reconstruction of genome-scale metabolic models of several species. However, these models often do not accurately predict biological phenotypes due to inherent insufficiencies, including metabolic gaps, unbalanced reactions, and lack of key physiological information.

We reconstructed the genome-scale metabolic model of S. aureus by combining genome annotation data, reaction stoichiometry and thermodynamic information, and regulation information from biochemical databases and previous strain-specific models 1-7, which were validated though our experimental observations. We then employed our model to identify metabolic-model driven genetic intervention strategies to combat the pathogenic activity of S. aureus. Reactions in the model were elemental and charge balanced. Upon manual and automated gap-filling, the model has 850 metabolic genes, 1437 metabolites and 1718 reactions that include inter-compartment transport and exchange reactions. To resolve the growth and no-growth inconsistencies in the model, we used an automated procedure called GrowMatch to reconcile the inconsistency predictions by suppressing or adding functionalities in the model while maintaining the already identified correct growth and no-growth predictions 8.

The extensive manual curation performed on the draft genome-scale reconstruction resulted in improved prediction capabilities while successfully capturing experimental results on growth inhibition. Our synthetic lethality analyses identified both intuitive and novel multiple gene-knockout strategies for reducing growth of Staphylococcusto a specific predetermined threshold. We performed correlation analyses between the synthetic lethal gene pairs to pinpoint the most probable candidates for genetic manipulations that fight the pathogenicity of S. aureus. We identified some experimentally-observed metabolic bottlenecks in wild-type and mutant growth, and predicted additional growth-inhibiting single- and double-knockouts which can potentially provide a solution to the prevailing antibiotic resistance of this organism.The results serve as a foundation from which to build, modify, and constantly improve, through the incorporation of future “-omics” data, the prediction and evaluation of novel therapeutic targets, thus, enhancing its functional utility and use as a resource to augment staphylococcal research worldwide.

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