In this study, two bacteria strains were used: A. vinelandii Deutsche Sammlung von Mikroorganismen und Zellkulturen (DSM) 2289 and B. subtilis DSM 10. A. vinelandii was grown in Burk’s medium (BM) (Newton et al., 1953 (link)), whereas B. subtilis was grown in a minimal mineral medium (MM).
Bacterial filtrates were produced as described elsewhere (Ferreira et al., 2019b (link)). Shortly, bacteria were grown in Fe-depleted media until siderophore concentration was stable (72 and 48 h for A. vinelandii and B subtilis, respectively). Bacterial biomass was pelleted by centrifugation, and the supernatant was filtered through a 0.45-µm pore size filter. The resulting filtrate was mixed with corn starch (5 and 15 g L−1 for B. subtilis and A. vinelandii, respectively), which was used as an anticaking agent. Then, the mixture was freeze dried (Labconco FreeZone 2.5 L coupled with a VacuuBrand RC 6 pump, USA). The resulting powder was homogenized and stored at 4°C until use.
Bacterial filtrates were produced as described elsewhere (Ferreira et al., 2019b (link)). Shortly, bacteria were grown in Fe-depleted media until siderophore concentration was stable (72 and 48 h for A. vinelandii and B subtilis, respectively). Bacterial biomass was pelleted by centrifugation, and the supernatant was filtered through a 0.45-µm pore size filter. The resulting filtrate was mixed with corn starch (5 and 15 g L−1 for B. subtilis and A. vinelandii, respectively), which was used as an anticaking agent. Then, the mixture was freeze dried (Labconco FreeZone 2.5 L coupled with a VacuuBrand RC 6 pump, USA). The resulting powder was homogenized and stored at 4°C until use.
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