Dl70 es

The supernatant was recovered by centrifugation (10,000 g for 15 min) and filtered at 0.22µm (GHP Acrodisc 25 mm syringe filter ; PALL). A volume of 10 mL was used to determine the concentrations of K, Na, P, Ca, Mg, Fe and Al in the different treatments. The analyses were done by inductively coupled plasma-atomic emission spectrometry (700 Series ICP-OES, Agilent Technologies). The pH was measured with a pH meter (DL70 ES, Mettler). Chemical analyses were performed for all replicates. The culture supernatant was also analyzed to determine the major organic acids released by the bacteria. These analyses were performed on an ion chromatography with conductivity detection (ICS 3000, Dionex Corp.) associated to an analytical column (IonPac® AS 11 HC, Dionex corp.) according to Balland et al. (2010) . The supernatants were eluted with KOH solutions of varying concentrations (0.9-60 mM) over time (step gradient) with a flow rate of 1.3 mL/min. Synthetic organic acids were used as references (sodium formate, D-gluconic acid, sodium butyrate, pyruvic acid sodium salt, sodium citrate tribasic, sodium oxalate, sodium propionate, sodium acetate, succinic acid disodium salt, DL-malic acid disodium salt, sodium-L-lactate and malonic acid disodium salt).

The 15 mL supernatants were analyzed for nutrients devoid in the initial solution and only present in the introduced mineral particles. The concentrations of Al and Fe in the BHm condition and Ca and P in the NBRIPm condition were determined by inductively coupled plasma-atomic emission spectrometry (700 Series ICP-OES, AGILENT TECHNOLOGIES). The pH was measured with a pH-meter (DL70 ES, METTLER). Chemical analyses were performed in all the independent replicates, except in the noninoculated treatments for which technical replicates were analyzed. Additionally, the mineral particles were collected and a subsample was observed using a Hitachi S2500 scanning electron microscope (SEM).