B094-0010
Phylogenetic conservatism of rhizosphere-competence traits of soil bacteria

Tuesday, 15 December 2020
Poster
Hee jung Cho1,2, Ulas Karaoz2, Kateryna Zhalnina3, Mary K Firestone2,4 and Eoin Brodie4,5, (1)University of California Berkeley, Plant and Microbial Biology, Berkeley, CA, United States, (2)Lawrence Berkeley National Laboratory, Climate and Ecosystem Sciences Division, Berkeley, CA, United States, (3)Lawrence Berkeley National Laboratory, Environmental Genomics and Systems Biology Division, Berkeley, CA, United States, (4)University of California Berkeley, Environmental Science, Policy, and Management, Berkeley, CA, United States, (5)Lawrence Berkeley National Laboratory, Berkeley, CA, United States
Abstract:
Bacterial fitness in the rhizosphere is governed by multiple traits and interactions with co-existing organisms in this soil environment. A growing plant root selects for different groups of bacteria as it moves through the soil, secreting changing combinations of substrates and shedding root debris throughout its development, providing organic C and other substrates for soil bacteria. Rhizosphere-adapted bacteria are a small subset of the soil microbiome suggesting that the traits selected upon are not well-dispersed through bacterial evolutionary history. Traits related to C substrate and nutrient (P, N, S) uptake and utilization, vitamin biosynthesis and antagonism or defense systems have all been reported to contribute to bacterial fitness in the rhizosphere. These traits vary in genetic complexity, and maybe be subject to vertical inheritance, horizontal gene transfer, or gene loss. In this study we evaluate the patterns of conservation in these potential fitness traits. Using a curated database of soil bacterial genomes (n=2731) derived from JGI GOLD we quantified the phylogenetic conservatism of bacterial traits that we hypothesize as being important for increased rhizosphere fitness. Using the consenTRAIT tool we explored how simple and complex traits varied in their conservation, as well as identifying signatures for horizontal gene transfer for recently acquired traits that modulate fitness in this niche.

We found the phylogenetic clustering of rhizosphere fitness to be weak in general, although specific substrate utilization traits related to aromatic organic acids utilization showed greater relatively clustering particularly within the Proteobacteria. This combined with other observations connecting aromatic organic acid utilization to rhizosphere fitness may help explain the frequent enrichment of Proteobacteria in the rhizosphere and help illuminate how plant and microbial traits interact to shape the soil microbiome and its contributions to biogeochemical cycling.

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