Interaction between phosphorus levels and a synthetic bacterial community on the dynamics of soil microbial biodiversity associated with SOM cycling

The low availability of phosphorus (P) in tropical soils limits productivity and soil organic matter (SOM) cycling. The use of synthetic bacterial communities (SynComs) designed for P solubilization and mineralization represents a biotechnological tool that can be used to seek the understanding of soil biochemical processes. This study investigated how the interaction between P levels and the inoculation of a SynCom can modulate the bacterial communities associated with SOM cycling in the maize rhizosphere. The SynCom consisted of isolates from the genera Bacillus, Burkholderia, and Klebsiella, characterized by 16S rRNA gene sequencing. Taxonomic diversity and functional prediction (PICRUSt2) were evaluated from amplicon sequencing data. Subsequent statistical analyses (R software) demonstrated that alpha diversity (Chao1 and Shannon indices) and global community structure (Beta diversity via Bray-Curtis) remained stable (p > 0.05). In contrast, functional prediction screening (evaluating 46 C cycle enzymes, 17 P cycle enzymes, and 19 P metabolic pathways) revealed that the interaction significantly affected (p < 0.05) the polygalacturonase enzyme (pectin degradation). Under P deprivation, the prediction indicated that the introduction of the SynCom possibly decreases the genetic potential of this enzyme compared to the uninoculated treatment. These data demonstrate that modulation in the rhizosphere can occur through fine functional adjustments in organic cycling, without causing massive taxonomic restructurings in the resident microbiome. Furthermore, the results highlight possible pathways that functional prediction as a bioinformatics tool enables for expanding the spectrum of investigation in microbiology associated with soil functioning.