Fig. 1. Growth curve of planktonic B. licheniformis in the culture medium under anaerobic conditions.

Fig. 2. OCP of X80 steel during 28-day immersing under sterile conditions or in B. licheniformis culture (Error bar: range of variation in measurement for 60 min).

Fig. 3. Pourbaix diagram of $\text{Fe}-{{\text{H}}_{2}}\text{PO}_{4}^{-}/\text{HPO}_{4}^{2-}-{{\text{H}}_{2}}\text{O}$ system based on thermodynamic calculation shown in Table 3. (The abbreviations st and in represent sterile and inoculated, respectively).

Fig. 4. EIS of X80 steel during 28-day immersing under sterile conditions (Left: Nyquist planes; Right: Bode diagrams; Scatter: Raw data; Line: fitting curves).

Fig. 5. EIS of X80 steel during 28-day immersing in B. licheniformis culture (Left: Nyquist planes; Right: Bode diagrams; Scatter: Raw data; Line: fitting curves).

Fig. 6. Fitted charge transfer resistance (Rct) of X80 steel during 28-day immersing under sterile conditions or in B. licheniformis culture.

Fig. 7. Cyclic polarization curves of X80 steel measured 3 d after immersing under sterile conditions or in B. licheniformis culture.

Fig. 8. Sectional morphology and compositions of B. licheniformis/X80 steel interface.

Fig. 9. TEM images of the FIB lift-out slice of B. licheniformis cell on the X80 steel surface.

Fig. 10. Pourbaix diagram of $\text{Fe}-{{\text{H}}_{2}}\text{PO}_{4}^{-}/\text{HPO}_{4}^{2-}-{{\text{H}}_{2}}\text{O}$ system including nitrate reduction based on thermodynamic calculation shown in Table 4.

Fig. 11. Schematic diagram of the mechanism of MIC of X80 steel by B. licheniformis under anaerobic conditions.