Bacterial tropism analysis

Anaerobic cultivation was performed according to the instructions of the Leibniz Institute DSMZ [79]. The Hungate anaerobic culture tube and Coy anaerobic chamber (Coy Laboratory Products, USA) were used in this experiment. BP01R2 was precultured in M9 minimal medium (248510; Becton Dickinson, USA) for 24 h, and then washed three times using the same method before use as an inoculant. The inoculant density was set at OD₆₀₀ = 0.01; the cultivation volume was 5 ml, and the culture was carried out by shaking at 120 rpm and 37°C. M9 minimal medium supplemented with 2 mM MgSO₄ (131-00405; FUJIFILM Wako, Japan), 0.1 mM CaCl₂ (21 075; Sigma-Aldrich, USA), 10 mM NaNO₃ (195-02545; FUJIFILM Wako, Japan), and 0.01% L-tryptophan (A10230; Alfa Aesar, USA) was prepared as a general incubation medium. Extra glucose was tested as an organic carbon resource at concentrations (w/v) of 0.4%, 0.2%, 0.04%, and 0%; the tube headspace gas was composed of either sterile air or 90% H₂ plus 10% CO₂ (N₂). Growth curves were measured at OD₅₉₅ using the PARADIG detection platform (Beckman, USA) or a Sunrise absorbance microplate reader (Tecan, Austria).