Microbial Implication of Iron Oxide Nanoparticles

Abstract

Magnetite nanoparticles (Fe3O4) designed for remediation will be intentionally released into the environment; however, little is known regarding their impact on bacterial populations. Research was conducted to 1) investigate the effect of Fe3O4 nanoparticles on bacterial growth in culture media and 2) evaluate the effect of Fe3O4 nanoparticles on bacterial survival in natural stream water. The effect of commercial and lab-prepared Fe3O4 nanoparticles was examined through growth experiments and observation of cell-nanoparticle interactions. Fe3O4 nanoparticles at 0.3, 0.6, and 1.0 g Fe/L were not inhibitory to the four organisms tested. Scanning electron microscopy was performed on precipitates formed in E. coli culture to examine the cell-nanoparticle interactions. Nanoparticles covered cell surfaces, but no damage to cell integrity was observed. Stabilized magnetite nanoparticles at 0.01 g Fe/L did not affect bacterial survival in stream water. Bacterial growth indicated by [3H]thymidine incorporation, however, decreased in the presence of nanoparticle suspensions. Growth inhibition was attributed to background electrolytes and nanoparticles themselves. Overall, magnetite nanoparticles did not affect bacteria in culture media or natural waters enough to indicate significant risk. Our results suggest that stabilized magnetite nanoparticles interact with bacterial surfaces without causing damage sufficient to inhibit cell growth.