Summary of gene and reaction essentiality analysis. (A) Categorization of the reactions present in the model based on their requirement for growth in SIS minimal media supplemented with succinate. About 25% of the reactions in the model are known or predicted to be required for growth under these conditions. (B) Distribution of essential gene products by COG functional classes. The total number of gene products in each class (essential + non-essential) represent only those present in the current model. The percentage of essential proteins in each class is indicated. COG classes depicted are those significantly enriched for essential gene products (p < 0.01, hypergeometric distribution).