Abstract

With the widespread use of metal organic framework materials (MOF), they inevitably enter the environment and pose potential threats to diverse organisms. Herein, we investigated the impacts of iron-based metal organic framework MIL-53(Fe) on the growth and the activity of nitrogen-fixing bacterium Azotobacter vinelandii. MIL-53(Fe) inhibited bacterial growth at a relatively low concentration (50 mg/L) and almost complete inhibition occurred at 140 mg/L. However, MIL-53(Fe) did not cause cell death even at high concentrations up to 130 mg/L. MIL-53(Fe) did not penetrate the cell wall and no cellular uptake was observed. MIL-53(Fe) lowered nifH gene expression of A. vinelandii, resulting in the attenuation of nitrogen fixation activity. MIL-53(Fe) did not arouse meaningful oxidative damage, but there were significant membrane leakage and pinholes in cell wall, indicating the mechanical damage. In addition, MIL-53(Fe) was stable in aqueous systems without obvious Fe release. After removing MIL-53(Fe) from the culture system, there was recovery of growth and nitrogen fixation activity of A. vinelandii that had initially been exposed to 10–130 mg/L of MIL-53(Fe), implying that the damage caused by MIL-53(Fe) to A. vinelandii was reversible. These findings highlighted the reversible environmental toxicity of MOF materials to microorganisms in the nitrogen cycle.

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