Isolation of a novel plant growth-promoting Dyella sp. from a Danish natural soil

Environmental soils are natural reservoirs of unexplored microbes, including potentially beneficial microbes to improve plant performance. Here, we isolated 75 bacterial strains from surface-sterilized roots of Arabidopsis thaliana (Arabidopsis) grown in a natural soil derived from an alder swamp. Culture-dependent isolation of individual strains from the roots followed by monoassociation-based screening identified seven bacteria that promoted Arabidopsis seedling weight. Of those, we identified a new species from the Dyella genus which increased biomass of tomato and Arabidopsis seedlings in agar as well as the shoot biomass of Arabidopsis grown in both the alder swamp soil and potting soil. Dyella sp. A4 specifically promoted the elongation of lateral roots without affecting lateral root number and primary root elongation. The new Dyella sp. A4 expands the toolbox of biostimulants for plant growth promotion via modulating root architecture.