Soil nutritional status and biogeography influence rhizosphere microbial communities associated with the invasive tree Acacia dealbata

Abstract

Invasiveness and the impacts of introduced plants are known to be mediated by plant-microbe interactions. Yet, the microbial communities associated with invasive plants are generally poorly understood. Here we report on the first comprehensive investigation of the bacterial and fungal communities inhabiting the rhizosphere and the surrounding bulk soil of a widespread invasive tree, Acacia dealbata. Amplicon sequencing data indicated that rhizospheric microbial communities differed significantly in structure and composition from those of the bulk soil. Two bacterial (Alphaproteobacteria and Gammaproteobacteria) and two fungal (Pezizomycetes and Agaricomycetes) classes were enriched in the rhizosphere compared with bulk soils. Changes in nutritional status, possibly induced by A. dealbata, primarily shaped rhizosphere soil communities. Despite a high degree of geographic variability in the diversity and composition of microbial communities, invasive A. dealbata populations shared a core of bacterial and fungal taxa, some of which are known to be involved in N and P cycling, while others are regarded as plant pathogens. Shotgun metagenomic analysis also showed that several functional genes related to plant growth promotion were overrepresented in the rhizospheres of A. dealbata. Overall, results suggest that rhizosphere microbes may contribute to the widespread success of this invader in novel environments.

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

“…In this study, based on shotgun metagenomic data, we substantiated and expanded the preliminary analysis performed by Kamutando et al [14] to better describe the genetic capacity of the bacterial communities in bulk and rhizosphere soil samples obtained from different A. dealbata populations. We also discuss several bacterial plant growth-promoting (PGP) traits.…”

“…Un-invaded natural ecosystems often have depleted nitrogen levels, hence bacteria that fix nitrogen may improve the competitive ability of these trees when growing in areas with poor nitrogen nutrition [52], thereby promoting their invasiveness [50,53]. It is therefore expected for such beneficial microbes to be enriched by their invasive host plants, as has been shown for A. dealbata [14].…”

“…Rhizosphere and non-rhizosphere (bulk) soil samples were collected as described previously [14]. Briefly, samples were collected from eight sites located in the grassland biome of South Africa.…”

“…These invasions also affect soil microbial community structure and composition by altering nutrient pools through processes like excessive leaf litter inputs (carbon) and biological nitrogen fixation (nitrogen) [13]. While the microbiome of A. dealbata has been characterized [14] and found to be enriched in bacteria of the classes Alpha-and Gammaproteobacteria, and in fungi of the classes Pezizomycetes and Agaricomycetes, the functional potential of these microbial communities remains unexplored. However, certain a priori hypotheses can be formulated for invasive legumes.…”

The first Taxus rhizosphere microbiome revealed by shotgun metagenomic sequencing

“…Compared with bulk soil, rhizosphere is significantly rich in genes associated with xenobiotic degradation and metabolism, and carbohydrate metabolism . In CAZy level 1 annotation, 14,232 Unigenes were identified as “Glycoside Hydrolases (GH),” followed by “Glycosyl Transferases” (GT; 9847), “Carbohydrate‐Binding Modules” (CBM; 6766), “Carbohydrate Esterases”(CE; 1632), “Auxiliary Activities” (AA; 1607), and “Polysaccharide Lyases” (PL; 318).…”