Different Impact of Suspended Al2O3 Nanoparticles on Microbial Communities: Formation of 2D-Networks (Without Humic Acids) or 3D-Colonies (With Humic Acids)

SARTORI, DAMIÁN RODRÍGUEZ; MIÑÁN, ALEJANDRO G.; GONZALEZ, MÓNICA C.; FERNÁNDEZ LORENZO DE MELE, MÓNICA A.

MICROBIAL ECOLOGY

SPRINGER

Año: 2022

0095-3628

The use of metal-based and, particularly, Al2O3 nanoparticles (Al2O3-NP) for diverse purposes is exponentially growing.However, the growth of such promissory market is not accompanied by a parallel extensive investigation related to the impactof this pollution on groundwater and biological systems. Pseudomonas species, ubiquitous, environmentally critical microbes,frequently respond to stress conditions with diverse strategies that generally include extracellular polymeric substances(EPS) formation. The aim of this study is to report that changes in the aqueous environment, particularly, the addition ofAl2O3-NP without and with humic acids, induce different adaptive strategies of Pseudomonas aeruginosa early biofilms. Tothis purpose, early biofilms were incubated in diluted culture media without (control) and with Al2O3-NP, and with humicacids (HA-control, HA-Al2O3-NP) for 24 h. 3D colonies with EPS strings and isolated bacteria in their surroundings weredetected in the control biofilms. Unlikely, an unusual adaptive behaviour was developed in the presence of Al2O3-NP. Bacteria opt to disassemble the 3D arrangements and to implement a 2D network promoting morphological and size changesof bacterial cells (small coccoid shapes). Remarkably, this strategy allows their temporarily non-EPS-depending survivalwithout decreasing the number of cells. This behaviour was not observed with ZnO-NP, HA-Al2O3-NP, or HA-ZnO-NP.Physicochemical analysis revealed that HA were adsorbed on Al2O3-NP and promoted the Al(III) ions complexation. Thissupports the hypothesis that the reduction of toxicity of Al ions and the 3D colony formation in the presence of HA-Al2O3-NP is promoted by the complexation of the metal ions with HA components