Essential metabolism for a minimal cell.

Area of Science:

• Synthetic biology
• Metabolic network reconstruction
• Minimal genome research

Background:

• JCVI-syn3A is a robust minimal cell with a compact genome (543 kbp) and 493 genes.
• Its precursor, *Mycoplasma mycoides capri*, offers extensive experimental data for network modeling.

Purpose of the Study:

• To construct a comprehensive metabolic network model for the JCVI-syn3A minimal cell.
• To compare in silico predictions with in vivo experimental data, including gene essentiality and mutagenesis.
• To identify knowledge gaps and propose future research directions for understanding the minimal genome.

Main Methods:

• Assembled a metabolic network using available experimental data from *Mycoplasma mycoides capri*.
• Validated the model against genome-scale in vivo transposon mutagenesis data.
• Compared in silico gene essentiality with in vivo essentiality and proteomics data.

Main Results:

• Achieved near-complete metabolic network reconstruction (98% of reactions supported).
• Model showed good agreement with in vivo mutagenesis experiments (MCC = 0.59).
• Identified high in vivo essentiality (92%) for genes in the reconstruction, exceeding in silico predictions (79%).

Conclusions:

• The metabolic model provides a coherent understanding of JCVI-syn3A's minimal metabolism.
• Discrepancies between model predictions and experimental data highlight areas for further investigation, including gene function and potential gene removals.
• Identification of 30 essential genes with unclear functions will drive research into novel biological mechanisms beyond core metabolism.