Tactic response of bacteria to zero-valent iron nanoparticles

8 páginas.-- 6 figuras.-- 33 referencias.-- Appendix A. Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.envpol.2016.01.093

The microbial assessment of pollutant toxicity rarely includes behavioral responses. In this study, we investigated the tactic response of Pseudomonas putida G7, a representative of soil bacterium, towards engineered zero-valent iron nanoparticles (nZVIs), as a new end-point assessment of toxicity. The study integrated the characterization of size distribution and charge of nZVIs and tactic reaction response by means of inverted capillary assay and computer-assisted motion analysis of motility behavior. Iron nanoparticles (diameter ≤ 100 nm) were prepared in the absence of oxygen to prevent aggregation, and then exposed in aerobic conditions. We first demonstrate that iron nanoparticles can elicit a negative tactic response in bacteria at low but environmentally-relevant, sub-lethal concentrations (1-10 μg/L). Cells were repelled by nZVIs in the concentration gradients created inside the capillaries, and a significant increase in turning events, characteristic of negative taxis, was detected under exposure to nZVIs. These tactic responses were not detectable after sustained exposure of the nanoparticles to oxygen. This new behavioral assessment may be prospected for the design of sensitive bioassays for nanomaterial toxicity.

Support for this research was provided by the Spanish Ministry of Economy and Competitiveness (CGL2010-22068-C02-01 and CGL2013-44554-R), Spanish Ministry of Education, Culture and Sport (mobility program for visiting scientists), and the Andalusian Government (RNM 2337). The authors also thank Prof. Peter J. Dobson, from The Queens College, Oxford, for useful discussions on this work and Mr Jonathan Jones (School of Chemistry) from the University of Bristol for performing TEM analysis.

Peer reviewed