Abstract
The application of Biolog EcoPlate™ for community-level physiological profiling of soils is well documented; however, the functional diversity of aquatic bacterial communities has been hardly studied. The objective of this study was to investigate the applicability of the Biolog EcoPlate™ technique and evaluate comparatively the applied endpoints, for the characterisation of the effects of metal oxide nanoparticles (MONPs) on freshwater microbial communities. Microcosm experiments were run to assess the effect of nano ZnO and nano TiO2 in freshwater at 0.8–100 mg/L concentration range. The average well colour development, substrate average well colour development, substrate richness, Shannon index and evenness, Simpson index, McIntosh index and Gini coefficient were determined to quantify the metabolic capabilities and functional diversity. Comprehensive analysis of the experimental data demonstrated that short-term exposure to TiO2 and ZnO NPs affected the metabolic activity at different extent and through different mechanisms of action. TiO2 NPs displayed lower impact on the metabolic profile showing up to 30% inhibition. However, the inhibitory effect of ZnO NPs reached 99% with clearly concentration-dependent responses. This study demonstrated that the McIntosh and Gini coefficients were well applicable and sensitive diversity indices. The parallel use of general metabolic capabilities and functional diversity indices may improve the output information of the ecological studies on microbial communities.
Highlights
ZnO at 100 mg/L concentration resulted in the highest inhibition (60 ± 21%), followed by the lower nano zinc oxide (nZnO) doses such as 20 mg/L, 4 mg/L and 0.8 mg/L nZnO, which caused 48 ± 20%, 23 ± 5% and 12 ± 1% inhibition compared to control, respectively
In line with studies about the effects of nanomaterials in aquatic and terrestrial systems performed with different methods we found a concentration- and time-dependent effect of nZnO on bacterial community [15,49,52]
By experimenting with TiO2 and ZnO NPs in freshwater lab-scale microcosms, it was shown that nTiO2 weakly influences microbial community, while ZnO nanoparticles have a strong effect on the metabolic activity and functional diversity of the microbiome
Summary
Nano titanium dioxide (nTiO2 ) and nano zinc oxide (nZnO) belong to the anthropogenic engineered metal oxide nanoparticles (MO-ENPs), the production and use of which was estimated to increase exponentially during the years owing to their extensive application in medicine, electronics, cosmetic and textile industry [4,5], but recently in modern agriculture [6]. The likeliness of nTiO2 and nZnO release into the environment is higher than that of other ENPs, given their high global production and consumption volume among the MONPs [7] and the several transport pathways. Once released into the aquatic environment, MONPs have been reported to be involved in homo- and hetero-aggregation followed by precipitation or sedimentation and accumulation [12,13,14,15]
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