Reconstruction and analysis of the genome-scale metabolic network of Streptococcus bovis B315 involved in lactic acid production in the rumen

Streptococcus bovis has been considered to be one of the starch utilizers and lactate producers in the rumen. By considering the role of S. bovis as main lactic acid producer, a large amount of biological information about this strain has been published. But there has not been a systematic analysis of metabolic capabilities for S. bovis so far. In the present study, the first genome-scale metabolic model of S. bovis (iStr472) was reconstructed based on the genome annotation of S. bovis B315. The model was analyzed in terms of sensitivity, topology and capabilities for utilization of other substrates. Results revealed that iStr472 comprises 694 reactions, 626 metabolites and 472 genes. The majority of reactions were located on the nucleotides metabolic pathway. The metabolic genes of model estimated as 27.6 % of all coding genes. Comparison of two models (iStr472 and ModelSEED) indicated that iStr472 has a higher accuracy and validity than the ModelSEED. The 16 highly connected metabolites were found in the model. The results of reaction deletion presented that the model has 126 vital reactions essential for the organism's growth. According to the model prediction, production of biomass was inversely influenced by lactate production. The iStr472 is also capable of utilizing fructose as carbon source. Taken together, it would be possible to use the predictions of iStr472 as a tool for better understanding the metabolism and metabolic engineering of S. bovis for reduced lactate production in the rumen.