Pseudomonas brassicacearum-Induced Biotite Weathering: Role of Iron Homeostasis and Two Siderophores

Soil bacteria play a crucial role in enhancing mineral weathering, thereby facilitating the release of mineral structural ions into the environment. Pseudomonas brassicacearum NFM421, a root-isolated bacterium, produces two different siderophores in the form of pyoverdine and ornicorrugatin. We studied the interaction between this bacterium and biotite─a natural iron-bearing phyllosilicate─to assess the factors governing siderophore-mediated biogenic weathering. We demonstrated that bacterial Fe is an essential factor driving biotite weathering. Our findings suggested that the lipopeptidic siderophore ornicorrugatin might be more effective than pyoverdine as an iron-bearing mineral weathering agent. This secondary siderophore's production is maintained even when the iron requirement of the bacteria is fulfilled. Moreover, we observed that another mechanism requiring direct physical contact might enable P. brassicacearum to acquire iron structural ions from soil minerals.