Rhizosphere soil nutrients and bacterial community diversity of four broad-leaved trees planted under Chinese fir stands with different stocking density levels

Acidobacteria represents an underrepresented soil bacterial phylum whose members are pervasive and copiously distributed across nearly all ecosystems. Acidobacterial sequences are abundant in soils and represent a significant fraction of soil microbial community. Being recalcitrant and difficult-to-cultivate under laboratory conditions, holistic, polyphasic approaches are required to study these refractive bacteria extensively. Acidobacteria possesses an inventory of genes involved in diverse metabolic pathways, as evidenced by their pan-genomic profiles. Because of their preponderance and ubiquity in the soil, speculations have been made regarding their dynamic roles in vital ecological processes viz., regulation of biogeochemical cycles, decomposition of biopolymers, exopolysaccharide secretion, and plant growth promotion. These bacteria are expected to have genes that might help in survival and competitive colonization in the rhizosphere, leading to the establishment of beneficial relationships with plants. Exploration of these genetic attributes and more in-depth insights into the belowground mechanics and dynamics would lead to a better understanding of the functions and ecological significance of this enigmatic phylum in the soil-plant environment. This review is an effort to provide a recent update into the diversity of genes in Acidobacteria useful for characterization, understanding ecological roles, and future biotechnological perspectives.

The rhizosphere microbiome is a central determinant of plant performance. Microbiome assembly has traditionally been investigated from a bottom-up perspective, assessing how resources such as root exudates drive microbiome assembly. However, the importance of predation as a driver of microbiome structure has to date largely remained overlooked. Here we review the importance of protists, a paraphyletic group of unicellular eukaryotes, as a key regulator of microbiome assembly. Protists can promote plant-beneficial functions within the microbiome, accelerate nutrient cycling, and remove pathogens. We conclude that protists form an essential component of the rhizosphere microbiome and that accounting for predator-prey interactions would greatly improve our ability to predict and manage microbiome function at the service of plant growth and health.