Challenging the impact of consortium diversity on bioaugmentation efficiency and native bacterial community structure in an acutely PAH-contaminated soil.

Polycyclic aromatic hydrocarbons (PAHs) are priority pollutants. We studied the effect of bioaugmentation using three allochthonous bacterial consortia with increasing diversity: SC AMBk, SC1, and SC4, on the structure and functionality of an artificially and acutely PAH-contaminated soil microbiome. The PAH supplementation increased substrate availability, allowing the inocula to efficiently degrade the supplemented PAHs after 15 days of incubation, become temporarily established, and modify the number of total interactions with soil residents. Sphingobium and Burkholderia, both members of the inoculants, were the major contributors to functional KOs (KEGG orthologs) linked to degradation and were differentially abundant genera in inoculated microcosms, indicating their competitiveness in the soil. Hence, bioaugmentation efficiency relied on them, while further degradation could be carried out by native microorganisms. This is one of the first studies to apply three inocula, designed from naturally occurring bacteria, and to study their effect on the soil's native community through ANCOM-BC. We revealed that when a resource that can be used by the inoculant is added to the soil, a high-diversity inoculant is not necessary to interact with the native community and establish itself. This finding is crucial for the design of microbiome engineering in bioremediation processes.