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Effects of sublethal doses of silver nanoparticles on B acillus subtilis planktonic and sessile cells
Author(s) -
Gambino M.,
Marzano V.,
Villa F.,
Vitali A.,
Vannini C.,
Landini P.,
Cappitelli F.
Publication year - 2015
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/jam.12779
Subject(s) - humanities , library science , art , art history , computer science
Aims Due to their antimicrobial activity, silver nanoparticles (Ag‐ NP s) are being increasingly used in a number of industrial products. The accumulation of Ag‐ NP s in the soil might affect plant growth‐promoting rhizobacteria and, in turn, the plants. We describe the effects of Ag‐ NP s on the soil bacteria Azotobacter vinelandii and Bacillus subtilis . Methods and Results In growth‐inhibition studies, A. vinelandii showed extreme sensitivity to Ag‐ NP s, compared to B. subtilis . We investigated the effects of Ag‐ NP s at subinhibitory concentrations, both on planktonic and sessile B. subtilis cells. As determined by 2,7‐dichlorofluorescein‐diacetate assays, Ag‐ NP s increase the formation of reactive oxygen species in planktonic cells, but not in sessile cells, suggesting the activation of scavenging systems in biofilms. Consistently, proteomic analysis in B. subtilis Ag‐ NP s‐treated biofilms showed increased production of proteins related to quorum sensing and involved in stress responses and redox sensing. Extracellular polysaccharides production and inorganic phosphate solubilization were also increased, possibly as part of a coordinated response to stress. Conclusions At low concentrations, Ag‐ NP s killed A. vinelandii and affected cellular processes in planktonic and sessile B. subtilis cells. Significance and Impact of the Study Re‐direction of gene expression, linked to selective toxicity, suggests a strong impact of Ag‐ NP s on soil bacterial communities.