Bacillus subtilis promotes plant phosphorus (P) acquisition through P solubilization and stimulation of root and root hair growth

Physiologia Plantarum, vol. 176, pp. e14338

Abstract

Bacteria can be applied as biofertilizers to improve crop growth in phosphorus (P)-limited conditions. However, their mode of action in a soil environment is still elusive. We used the strain ALC_02 as a case study to elucidate how Bacillus subtilis affects dwarf tomato cultivated in soil-filled rhizoboxes over time. ALC_02 improved plant P acquisition by increasing the size and P content of P-limited plants. We assessed three possible mechanisms, namely root growth stimulation, root hair elongation, and solubilization of soil P. ALC_02 produced auxin, and inoculation with ALC_02 promoted root growth. ALC_02 promoted root hair elongation as the earliest observed response and colonized root hairs specifically. Root and root hair growth stimulation was associated with a subsequent increase in plant P content, indicating that a better soil exploration by the root system improved plant P acquisition. Furthermore, ALC_02 affected the plant-available P content in sterilized soil differently over time and released P from native P pools in the soil. Collectively, ALC_02 exhibited all three mechanisms in a soil environment. To our knowledge, bacterial P biofertilizers have not been reported to colonize and elongate root hairs in the soil so far, and we propose that these traits contribute to the overall effect of ALC_02. The knowledge gained in this research can be applied in the future quest for bacterial P biofertilizers, where we recommend assessing all three parameters, not only root growth and P solubilization, but also root hair elongation. This will ultimately support the development of sustainable agricultural practices.

Authors 10

1. Camilla Niketa Gadomska Jensen

   University of Copenhagen · Novonesis (Denmark)

   Affiliation as printed

   Department of Plant and Environmental Sciences University of Copenhagen Frederiksberg Denmark

   Plant Health Innovation Novonesis A/S Taastrup Denmark

   Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg, Denmark

   Plant Health Innovation, Novonesis A/S, Taastrup, Denmark

2. Janet Ka Yan Pang

   Technical University of Denmark

   Affiliation as printed

   Bacterial Interactions and Evolution Group, DTU Bioengineering Technical University of Denmark Kgs. Lyngby Denmark

   Bacterial Interactions and Evolution Group, DTU Bioengineering, Technical University of Denmark, Kgs. Lyngby, Denmark

3. Stjepan Krešimir Kračun

   Novonesis (Denmark)

   Affiliation as printed

   R&D Microbial Screening R&D Microbe & Culture Research Novonesis A/S Hørsholm Denmark

4. Birgit Albrecht Svendsen

   Novonesis (Denmark)

   Affiliation as printed

   R&D Microbial Screening R&D Microbe & Culture Research Novonesis A/S Hørsholm Denmark

5. Kristian Fog Nielsen

   Novonesis (Denmark)

   Affiliation as printed

   Biochemical Assays Novonesis A/S Hørsholm Denmark

6. Ákos T. Kovács Aachen Institute of Biology Leiden University Leiden The Netherlands Institute of Biology, Leiden University

   Leiden University · Technical University of Denmark

   Affiliation as printed

   Bacterial Interactions and Evolution Group, DTU Bioengineering Technical University of Denmark Kgs. Lyngby Denmark

   Institute of Biology Leiden University Leiden the Netherlands

   Bacterial Interactions and Evolution Group, DTU Bioengineering, Technical University of Denmark, Kgs. Lyngby, Denmark

   Institute of Biology, Leiden University, Leiden, the Netherlands

7. Lars Moelbak

   Novonesis (Denmark)

   Affiliation as printed

   Plant Health Innovation Novonesis A/S Taastrup Denmark

   Plant Health Innovation, Novonesis A/S, Taastrup, Denmark

8. Lorenzo Fimognari

   Novonesis (Denmark)

   Affiliation as printed

   Plant Health Innovation Novonesis A/S Taastrup Denmark

   Plant Health Innovation, Novonesis A/S, Taastrup, Denmark

9. Steen Husted

   University of Copenhagen

   Affiliation as printed

   Department of Plant and Environmental Sciences University of Copenhagen Frederiksberg Denmark

   Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg, Denmark

10. Alexander Schulz corresponding

    University of Copenhagen

    Affiliation as printed

    Department of Plant and Environmental Sciences University of Copenhagen Frederiksberg Denmark

    Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg, Denmark