Effects on iron nanoparticles on pseudomonas aeruginosa biofilms

Date of Award


Degree Name

M.S. in Biology


Department of Biology


Advisor: Jayne B. Robinson


Iron oxide nanoparticles are among the most commercially important nanoparticles being used in this burgeoning industry. Research has shown iron nanoparticles to have an inhibitory effect against several different genera of bacteria: Staphylococcus, Bacillus and Pseudmonas spp. In this study we looked at the effect of three different sets of Fe3O4 nanoparticles (FeNPs) on the development of Pseudomonas aeruginosa PAO1 biofilms. Two of these NPs are also referred to as SPIONs (superparamagnetic iron oxide nanoparticles). Exposure of cells to these FeNPs at concentrations up to 200μg/ml resulted in an increase in biofilm biomass by 16h under static conditions and a corresponding increase in cell density in the bulk liquid. In contrast, these biofilms had decreased levels of extracellular DNA (eDNA). Fe(II) levels in the supernatants of biofilms formed in the presence of FeNPs exceeded 100μM compared with 20μM in control media without cells. Spent cell supernatants had little effect on Fe(II) levels. Cells also had an effect on the aggregation behavior of these nanoparticles. FeNPs incubated with cells exhibited a decrease in the number and size of FeNP aggregates visible using light microscopy. Additionally, FeNPs incubated with cells were altered in their response upon exposure to a supermagnet. When exposed to a supermagnet FeNPs in fresh media or spent culture supernatants formed large aggregates visible in the light microscope, and could be pelleted in microtitre plate wells. In contrast, FeNPs incubated with cells were unaffected by exposure to the supermagnet and could not be pelleted. The results of this study indicate a need to reconsider the effects of FeNPs on bacterial growth and biofilm formation and the effect the bacterial cells may have on the use and recovery of SPIONs.


Pseudomonas aeruginosa Effect of iron on, Ferric oxide Magnetic properties, Biofilms Inhibitors

Rights Statement

Copyright 2011, author