Phylogenetic organization of bacterial activity

Abstract

Phylogeny is an ecologically meaningful way to classify plants and animals, as closely related taxa frequently have similar ecological characteristics, functional traits and effects on ecosystem processes. For bacteria, however, phylogeny has been argued to be an unreliable indicator of an organism's ecology owing to evolutionary processes more common to microbes such as gene loss and lateral gene transfer, as well as convergent evolution. Here we use advanced stable isotope probing with (13)C and (18)O to show that evolutionary history has ecological significance for in situ bacterial activity. Phylogenetic organization in the activity of bacteria sets the stage for characterizing the functional attributes of bacterial taxonomic groups. Connecting identity with function in this way will allow scientists to begin building a mechanistic understanding of how bacterial community composition regulates critical ecosystem functions.

Figure 1

Phylogenetic tree (based on 16S rRNA gene sequences) and isotope incorporation of bacterial taxa in soil. Bars are proportional to the excess atom fraction of ¹⁸O or ¹³C of each taxon's DNA after incubation with ¹³C-glucose (blue) or H₂¹⁸O in the presence (green) or absence (red) of natural abundance glucose. Tree is colored by the phylogenetic group.

Figure 2

Variation in excess atom fraction of ¹⁸O or ¹³C of each taxon's DNA after incubation with ¹³C-glucose (blue) or H₂¹⁸O in the presence (green) or absence (red) of natural abundance glucose explained by group membership at different taxonomic levels. Values reflect linear model results for groups with a minimum of five member taxa.