Effects of humic acid on the interactions between zinc oxide nanoparticles and bacterial biofilms

Kai Ouyang; Xiao Ying Yu; Yunlin Zhu; Chunhui Gao; Qiaoyun Huang; Peng Cai

doi:10.1016/j.envpol.2017.07.003

Effects of humic acid on the interactions between zinc oxide nanoparticles and bacterial biofilms

Kai Ouyang, Xiao Ying Yu, Yunlin Zhu, Chunhui Gao, Qiaoyun Huang, Peng Cai

Research output: Contribution to journal › Article › peer-review

44 Scopus citations

Abstract

The effects of humic acid (HA) on interactions between ZnO nanoparticles (ZnO NPs) and Pseudomonas putida KT2440 biofilms at different maturity stages were investigated. Three stages of biofilm development were identified according to bacterial adenosine triphosphate (ATP) activity associated with biofilm development process. In the initial biofilm stage 1, the ATP content of bacteria was reduced by more than 90% when biofilms were exposed to ZnO NPs. However, in the mature biofilm stages 2 and 3, the ATP content was only slightly decreased. Biofilms at stage 3 exhibited less susceptibility to ZnO NPs than biofilms at stage 2. These results suggest that more mature biofilms have a significantly higher tolerance to ZnO NPs compared to young biofilms. In addition, biofilms with intact extracellular polymeric substances (EPS) showed higher tolerance to ZnO NPs than those without EPS, indicating that EPS play a key role in alleviating the toxic effects of ZnO NPs. In both pure ZnO NPs and ZnO-HA mixtures, dissolved Zn²⁺ originating from the NPs significantly contributed to the overall toxicity. The presence of HA dramatically decreased the toxicity of ZnO NPs due to the binding of Zn²⁺ on HA. The combined results from this work suggest that the biofilm maturity stages and environmental constituents (such as humic acid) are important factors to consider when evaluating potential risks of NPs to ecological systems.

Original language	English
Pages (from-to)	1104-1111
Number of pages	8
Journal	Environmental Pollution
Volume	231
DOIs	https://doi.org/10.1016/j.envpol.2017.07.003
State	Published - 2017
Externally published	Yes

Funding

This work was supported by the National Natural Science Foundation of China ( 41522106 ), the National Key Research Program of China ( 2016YFD0800206 ), and the National Basic Research Program of China ( 2015CB150504 ). Dr. X-Y Yu is grateful to the Pacific Northwest National Laboratory Earth and Biological Sciences Mission Seed Laboratory Directed Research and Development fund ( 90001 ) for support. Appendix A

Funders	Funder number
Laboratory Directed Research and Development	90001
Pacific Northwest National Laboratory
National Natural Science Foundation of China	41522106
Basic Research Program of Jiangsu Province	2015CB150504
Zhengzhou Tobacco Research Institute, China National Tobacco Corporation	2016YFD0800206

Keywords

Different stages of maturity
Dissolved Zn
Humic acid
Pseudomonas putida KT2440 biofilm
Zinc oxide nanoparticle

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title = "Effects of humic acid on the interactions between zinc oxide nanoparticles and bacterial biofilms",

abstract = "The effects of humic acid (HA) on interactions between ZnO nanoparticles (ZnO NPs) and Pseudomonas putida KT2440 biofilms at different maturity stages were investigated. Three stages of biofilm development were identified according to bacterial adenosine triphosphate (ATP) activity associated with biofilm development process. In the initial biofilm stage 1, the ATP content of bacteria was reduced by more than 90% when biofilms were exposed to ZnO NPs. However, in the mature biofilm stages 2 and 3, the ATP content was only slightly decreased. Biofilms at stage 3 exhibited less susceptibility to ZnO NPs than biofilms at stage 2. These results suggest that more mature biofilms have a significantly higher tolerance to ZnO NPs compared to young biofilms. In addition, biofilms with intact extracellular polymeric substances (EPS) showed higher tolerance to ZnO NPs than those without EPS, indicating that EPS play a key role in alleviating the toxic effects of ZnO NPs. In both pure ZnO NPs and ZnO-HA mixtures, dissolved Zn2+ originating from the NPs significantly contributed to the overall toxicity. The presence of HA dramatically decreased the toxicity of ZnO NPs due to the binding of Zn2+ on HA. The combined results from this work suggest that the biofilm maturity stages and environmental constituents (such as humic acid) are important factors to consider when evaluating potential risks of NPs to ecological systems.",

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doi = "10.1016/j.envpol.2017.07.003",

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AU - Cai, Peng

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AB - The effects of humic acid (HA) on interactions between ZnO nanoparticles (ZnO NPs) and Pseudomonas putida KT2440 biofilms at different maturity stages were investigated. Three stages of biofilm development were identified according to bacterial adenosine triphosphate (ATP) activity associated with biofilm development process. In the initial biofilm stage 1, the ATP content of bacteria was reduced by more than 90% when biofilms were exposed to ZnO NPs. However, in the mature biofilm stages 2 and 3, the ATP content was only slightly decreased. Biofilms at stage 3 exhibited less susceptibility to ZnO NPs than biofilms at stage 2. These results suggest that more mature biofilms have a significantly higher tolerance to ZnO NPs compared to young biofilms. In addition, biofilms with intact extracellular polymeric substances (EPS) showed higher tolerance to ZnO NPs than those without EPS, indicating that EPS play a key role in alleviating the toxic effects of ZnO NPs. In both pure ZnO NPs and ZnO-HA mixtures, dissolved Zn2+ originating from the NPs significantly contributed to the overall toxicity. The presence of HA dramatically decreased the toxicity of ZnO NPs due to the binding of Zn2+ on HA. The combined results from this work suggest that the biofilm maturity stages and environmental constituents (such as humic acid) are important factors to consider when evaluating potential risks of NPs to ecological systems.

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Effects of humic acid on the interactions between zinc oxide nanoparticles and bacterial biofilms

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