title: Effects of sublethal concentrations of silver nanoparticles on Escherichia coli and Bacillus subtilis under aerobic and anaerobic conditions.
abstract: The present work is aimed at comparing the effects of sublethal concentrations of silver nanoparticles (AgNPs) on the growth kinetic, adhesion ability, oxidative stress, and phenotypic changes of model bacteria (Escherichia coli and Bacillus subtilis) under both aerobic and anaerobic conditions. Growth kinetic tests conducted in 96-well microtiter plates revealed that sublethal concentrations of AgNPs do not affect E. coli growth, whereas 1 μg/ml AgNPs increased B. subtilis growth rate under aerobic conditions. At the same concentration, AgNPs promoted B. subtilis adhesion, while it discouraged E. coli attachment to the surface in the presence of oxygen. As determined by 2,7-dichlorofluorescein-diacetate assays, AgNPs increased the formation of intracellular reactive oxygen species, but not at the highest concentrations, suggesting the activation of scavenging systems. Finally, motility assays revealed that 0.01 and 1 μg/ml AgNPs, respectively, promoted surface movement in E. coli and B. subtilis under aerobic and anaerobic conditions. The results demonstrate that E. coli and B. subtilis react differently from AgNPs over a wide range of sublethal concentrations examined under both aerobic and anaerobic conditions. These findings will help elucidate the behavior and impact of engineered nanoparticles on microbial ecosystems.
authors.affiliation: Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente, Università degli Studi di Milano, via Celoria 2, 20133 Milano, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Garuglieri
authors.affiliation: Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente, Università degli Studi di Milano, via Celoria 2, 20133 Milano, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Cattò
authors.affiliation: Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente, Università degli Studi di Milano, via Celoria 2, 20133 Milano, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Villa
authors.affiliation: Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente, Università degli Studi di Milano, via Celoria 2, 20133 Milano, Italy.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Zanchi
authors.affiliation: Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente, Università degli Studi di Milano, via Celoria 2, 20133 Milano, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Cappitelli
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001412:Bacillus subtilis / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D001422:Bacterial Adhesion / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D008124:Locomotion / Q000187:drug effects; D053758:Nanoparticles / Q000378:metabolism*; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000032:analysis; D012834:Silver / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D017382:Reactive Oxygen Species; D012834:Silver