Density map of the role of the nodes in the E. coli network that are conserved or deleted in Buchnera, according to the procedure described in . The degree of participation measures the connection of a given node with the nodes from modules other than its own. The within-module degree measures the connection of the node with other nodes within its own module. Peripheral nodes show both low participation and low within-module degree. Non-hub connectors participate significantly and with a low degree of within-module connections, while connector hubs have both high participation and high degree of within-module connections . Connector hubs and non-hub connectors are mainly conserved in the Buchnera network, while the deletion of nodes mainly affects peripheral nodes. The measures are calculated as in , based on the modular division of the E. coli network obtained from the Butland dataset. The scale refers to the number of nodes in each position.