Fig. 2. Variovorax (node 55) is a network hub predicted to be important for thiamine production in the bioreactor communities.

a Network analysis based on sparCC correlation across 92 metagenomes was used to predict associations of microorganisms with other members. The nodes with the greatest betweenness centrality were delineated as network hubs and are numbered. Four of these network hubs (b) encode genes for the biosynthesis of thiamine (vitamin B1). Of these four hubs (c) Variovorax (Node) 55 shows the greatest importance for correlated auxotrophic members based on thiamine-hubness metrics which considers the degree, connections to B1-deficient nodes, and the number of connections those B1-deficient nodes have to B1-producers. d Distribution of calculated vitamin hub metric scores of Variovorax (Node 55), given the network shown in a, after randomly assigning 38 nodes within the network the capacity to produce thiamine, over 1000 simulations. e Variovorax is present in communities with many other bacteria able to produce thiamine but is correlated almost exclusively with thiamine auxotrophs within bioreactor communities. The rank abundance curve of the relative abundance of the 44 most prevalent microorganisms in bioreactor sample SCN18_30_10_14_R1_P is shown as an example of this phenomenon.