Ferromanganese nodules are an important mineral resource in the seafloor; however, the genetic mechanism is still unknown. The biomineralization of microorganisms appears to promote ferromanganese nodule formation. To investigate the possible mechanism of microbial–ferromanganese nodule interaction, to test the possibility of marine microorganisms as deposition template for ferromanganese nodules minerals, the interactions between Jeotgalibacillus campisalis strain CW126-A03 and ferromanganese nodules were studied. The results showed that strain CW126-A03 increased ion concentrations of Fe, Mn, and other metal elements in solutions at first. Then, metal ions were accumulated on the cells’ surface and formed ultra-micro sized mineral particles, even crystalline minerals. Strain CW126-A03 appeared to release major elements in ferromanganese nodules, and the cell surface may be a nucleation site for mineral precipitation. This finding highlights the potentially important role of biologically induced mineralization (BIM) in ferromanganese nodule formation. This BIM hypothesis provides another perspective for understanding ferromanganese nodules’ genetic mechanism, indicating the potential of microorganisms in nodule formation.