The Functional Potential of the Rhizospheric Microbiome of an Invasive Tree Species, Acacia dealbata

Abstract

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.

Metagenomic Functional Shifts to Plant Induced Environmental Changes

“…Proteobacteria , Acidobacteria , and Actinobacteria were the predominant bacterial phyla in both bulk soil and rhizosphere samples. A similar taxonomic profile of soil microbiomes obtained by shotgun metagenome analysis was previously reported (Fonseca et al, 2018; Kamutando et al, 2018). A versatile soil bacteria capable of carbon and nitrogen fixation, Rhodopseudomonas palustris , was the most abundant bacterial species represented by >14% of all high-quality reads (Supplementary Table S3) and Rhodococcus erythropolis capable of degrading, toluene, naphthalene, herbicides, and other environmental pollutants (Curragh et al, 1994), was represented by ∼1% of all high-quality reads.…”

“…It is occupied by highly diverse microbial communities which are structurally and functionally influenced by plant and soil type (Philippot et al, 2013). Many previous studies of the metabolic capabilities of plant-associated microbiomes have identified specific functions linked to plant–microbiomes interaction, such as cell motility and root adhesion, metabolism of nitrogen, carbohydrates and vitamins, and xenobiotic degradation (Bulgarelli et al, 2015; Yan et al, 2017; Kamutando et al, 2018). However, it is not clear how these rhizosphere-specific (RS) functions are incorporated into the overall metabolic capabilities of soil microbiomes in general.…”

Soil biotic and abiotic conditions negate invasive species performance in native habitat

“…Several studies with biogeographic comparison of invasive species in their native range and invaded range focus on the impact of variable soil microbes on plant performance (Callaway and Aschehoug 2000;Hierro et al 2005;Vermeij et al 2009;Volin et al 2010). While there is increased research interest in the microbiome of invasive species (Coats and Rumpho 2014;Kamutando et al 2019;Ramirez et al 2019), there is limited information on the performance of invasive plants in their native habitats and the restrictions posed by the soil characteristics. For example, soil pH has complex effect on plant growth leading to the variation in the distribution of plant species in acidic or calcareous soils.…”

Herbicidal properties of the commercial formulation of methyl cinnamate, a natural compound in the invasive silver wattle (Acacia dealbata)

“…Allelopathy differentially contributes to the invasion process of A. dealbata (Aguilera et al 2015a(Aguilera et al , 2015b(Aguilera et al , 2015cLorenzo et al 2017). However, this invasive species has largely shown a potential allelopathic or phytotoxic effect on different physiological parameters of plants (Aguilera et al 2015a(Aguilera et al , 2015b(Aguilera et al , 2015cLorenzo et al 2008Lorenzo et al , 2010aLorenzo et al , 2011Lorenzo et al , 2016Lorenzo et al , 2019Reigosa and Carballeira 2017a) and soil microbes (Kamutando et al 2019;Lorenzo et al 2013).…”