PathwayLinks: Network analysis of metabolic pathways across bacterial organisms in a community

The Human Microbiome Project (HMP) recognizes that several microbiome environments reside within the human body (such as the mouth and the GI tract). HMP is involved in documenting and sequencing bacteria existing in these environments. These environments can be considered to host a community of bacteria, where one bacterium may provide support for the metabolic needs of other bacteria. Publicly available metabolic pathway information exists for many of these organisms, most notably the well-established KEGG database. To predict the metabolic relationships that exist between organisms living in a community, we analyzed publicly available metabolic data and developed a set of procedures whose input is a set of organisms in a community and whose output is a set of predictions of possible metabolic linkages between them. We refer to these procedures collectively as the PathwayLinks procedures, as they find possible links between metabolic pathways. A pilot study was conducted using the well-known Red-Complex of bacteria in the mouth, which is linked to gingivitis. Results indicate that the Citrulline and Protoporphyrin metabolites may link two of the key organisms in the complex. This research shows promise in providing a theoretical basis for predicting metabolic relationships between bacteria living in a community.