The Functional Potential of the Rhizospheric Microbiome of an Invasive Tree Species, Acacia dealbata
Plant-microbe interactions mediate both the invasiveness of introduced plant species and the impacts that they have in invaded ecosystems. Although the phylogenetic composition of the rhizospheric microbiome of Acacia dealbata (an invasive Australian tree species) has been investigated, little is known about the functional potential of the constituents of these altered microbial communities. We used shotgun DNA sequencing to better understand the link between bacterial community composition and functional capacity in the rhizospheric microbiomes associated with invasive A. dealbata populations in South Africa. Our analysis showed that several genes associated with plant growth-promoting (PGP) traits were significantly overrepresented in the rhizospheric metagenomes compared to neighbouring bulk soils collected away from A. dealbata stands. The majority of these genes are involved in the metabolism of nitrogen, carbohydrates and vitamins, and in various membrane transport systems. Overrepresented genes were linked to a limited number of bacterial taxa, mostly Bradyrhizobium species, the preferred N-fixing rhizobial symbiont of Australian acacias. Overall, these findings suggest that A. dealbata enriches rhizosphere soils with potentially beneficial microbial taxa, and that members of the genus Bradyrhizobium may play an integral role in mediating PGP processes that may influence the success of this invader when colonizing novel environments.
KeywordsBiological invasions Bradyrhizobium Plant growth-promoting traits Rhizosphere microbiome Shotgun sequencing Tree invasions
We thank Lesley Henderson, Fanus Venter and Emma Steenkamp for the information on A. dealbata populations.
A.V., T.P.M., J.J.LR., D.M.R. and D.A.C. designed the research. C.N.K. and G.K.N performed the research. C.N.K., S.V. and A.V. analysed the data. C.N.K and A.V wrote the manuscript. All authors commented on the manuscript at all stages.
Funding for this research was provided by the National Research Foundation, South Africa (Grant No. CPRR14071676470 to AV).
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