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Toxicity of silver nanoparticles in the bacterium Pseudomonas putida

Dong, Feng (2016)
Ph.D. thesis, University of Birmingham.

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This thesis investigated the toxicity of silver nanoparticles (AgNPs) in the bacterium Pseudomonas putida. It is unclear whether the antimicrobial activities of AgNPs are exclusively mediated by the release of silver ions (Ag\(^+\)) or, instead, are due to combined nanoparticle and ions effects. First, a method to measure dissolved Ag in Ag\(^+\)/AgNPs mixtures was developed by combining aggregation of AgNPs with centrifugation. The AgNP stocks were stored in an anoxic environment. Silver nanoparticles underwent different degrees of aggregation and dissolution in Davis minimal medium. Silver ions had stronger toxicity than AgNPs. The minimum inhibitory concentrations of Ag+ and AgNPs for P. putida steadily increased with increasing initial cell densities. Silver nanoparticles acted as a Ag reservoir, releasing Ag\(^+\) to kill bacteria. The toxicity of AgNPs was dominated by dissolved Ag. In an evolution experiment, P. putida populations evolved for ~500 generations under the treatment of Ag\(^+\) or AgNPs. The mutations in the evolved populations stressed by Ag\(^+\) and AgNPs displayed different patterns. The nonsynonymous mutations in AgNP-stressed populations were mostly associated with cell surface proteins, and Ag\(^+\) stress selected for mutations in cytoplasmic proteins linked to metal metabolism, suggesting different toxicity mechanisms of Ag\(^+\) and AgNPs.

Type of Work:Ph.D. thesis.
Supervisor(s):Kreft, Jan and Valsami-Jones, Eugenia and Lead, Jamie R.
School/Faculty:Colleges (2008 onwards) > College of Life & Environmental Sciences
Department:School of Biosciences
Additional Information:

Publications arising from thesis:

Feng Dong, Eugenia Valsami-Jones, Jan-Ulrich Kreft (2016) New, rapid method to measure dissolved silver concentration in silver nanoparticle suspensions by aggregation combined with centrifugation. Journal of Nanoparticle Research 18(9): 1-12.

Subjects:QD Chemistry
QR Microbiology
Institution:University of Birmingham
ID Code:7085
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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