Isolation of a Novel Plant Growth-Promoting Dyella sp. from 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.