PCA analysis of the soil characteristics from the 40 soils samples (numbered black circles) that were used for bacterial isolation.

<p>The percentages show how much variation is explained by each principal component. The soils with higher pH, organic matter (OM), potassium (K), phosphorus (P), and clay (Clay) contents are plotted to the right. There are three clusters along the first principal component (PC1) that grouped the soils by overall richness. Based on these clusters, all 40 of the soil samples were classified according to their overall soil richness: poor, average or rich. The appropriate soil richness was attributed to each bacterial isolate (according to its origin) before further analysis. Supervised statistics of these data on <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116020#pone.0116020.s001" target="_blank">S1 Fig</a>.