Abstract. Natural minerals in soil can inhibit the growth of bacteria that protect
organic carbon from decay. However, the mechanism inhibiting the bacterial
growth remains poorly understood. Here, using a series of cultivation
experiments and biological, chemical and synchrotron-based spectral analyses,
we showed that kaolinite, hematite, goethite and ferrihydrite had a
significant inhibitory effect on the growth of the model bacteria
Pseudomonas brassicacearum J12, which was more prominent with a
concentration of 25 mg mL−1 than it was with either 10 or
5 mg mL−1. In contrast, montmorillonite promoted the growth of J12.
Compared to Al-containing minerals, Fe(III)-containing minerals produced more
hydroxyl radical (HO⚫) that has high efficiency for the
inhibition of J12. Moreover, a significant positive correlation between
HO⚫ radical and Fe(II) was found, suggesting that Fe(II)
contributes to the generation of HO⚫. Furthermore, both
micro X-ray fluorescence and X-ray photoelectron spectroscopies indicated
that surface Fe(III) was reduced to Fe(II), which can produce
HO⚫ through the well-known Fenton reaction series. Together,
these findings indicate that the reduced surface Fe(II) derived from
Fe(III)-containing minerals inhibits the growth of Pseudomonas brassicacearum J12 via a free-radical mechanism, which may serve as a
ubiquitous mechanism between iron minerals and all of the heterotrophic
bacteria in view of taxonomically and ecologically diverse heterotrophic
bacteria from terrestrial environments as a vast source of superoxide.
Supplementary material to "Iron minerals inhibit the growth of bacteria via a free-radical mechanism: Implications for soil carbon storage"
