This study is aimed to explore the toxicity of TiO2 nanoparticles at low concentrations (0.25, 0.50 &amp; 1.00 μg/ml); on five bacterial isolates and their consortium in waste water medium both in dark and UVA conditions. To critically examine the toxic effects of nanoparticles and the response mechanism(s) offered by microbes, several aspects were monitored viz. cell viability, ROS generation, SOD activity, membrane permeability, EPS release and biofilm formation. A dose and time dependent loss in viability was observed for treated isolates and the consortium. At the highest dose, after 24h, oxidative stress was examined which conclusively showed more ROS generation &amp; cell permeability and less SOD activity in single isolates as compared to the consortium. As a defense mechanism, EPS release was enhanced in case of the consortium against the single isolates, and was observed to be dose dependent. Similar results were noticed for biofilm formation, which substantially increased at highest dose of nanoparticle exposure. Concluding, the consortium showed more resistance against the toxic effects of the TiO2 nanoparticles compared to the individual isolates. © 2015 Mathur et al.This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Amitava Mukherjee

Centre for Nanobiotechnology

Vellore Campus

Chandra Sekaran N

Mathur A

Kumari J

Parashar A

Lavanya T

Fulltext

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

PLOS ONE

Sulfate-reducing bacteria are one of the most commonly occurring strains in industrial and waste water samples. TiO2 NPs (titanium dioxide nanoparticles) are an important component of cosmetics and toothpastes and are also useful agents as disinfectants in treatment of wastewater. The study delineates the effect of TiO2 NPs on sulfate-reducing bacteria (Desulphovibrio desulfuricans and Desulfotomaculum nigrificans) and their consortium. The specific growth of these bacteria under UVA, visible light, and dark was found to be exposure dependent. With an increase in the concentration of TiO2 NPs, insignificant changes were observed in the sulfate reduction rate. The specific growth rate of bacteria was reduced upon exposure of 1 μg/mL of TiO2, whereas lower concentrations did not have any significant impact. The exopolymer release, which is indicative of the bacterial defense response, demonstrated a nanoparticle exposure-dependent increase over time, and it was significantly higher in the consortium as compared to individual strains. Similarly, the biofilm thickness and density showed a linear dependence on the NP exposure time. The surface chemical changes of exopolymers were analyzed with help of FT-IR analysis. Distortion of the consortium cells embedded within the biofilm matrix when exposed with the highest exposure dose of NPs and UV was prominent as compared to control cells. The consortium demonstrated enhanced ability to counter stress under all the experimental conditions as compared with the single bacterial strains. The sulfate-reducing potency of these bacteria under low exposure concentrations of TiO2 NPs could be used as a bioremediation tool in wastewater treatment plants. © 2017 Published by Elsevier Ltd.

Journal of Environmental Chemical Engineering

The effect of TiO2 nanoparticles on sulfate-reducing bacteria and their consortium under anaerobic conditions

P25 TiO2 nanoparticles majorly used in cosmetic products have well known detrimental effects towards the aquatic environment. In a freshwater ecosystem, Chlorella and Scenedesmus are among the most commonly found algal species frequently used to study the effects of metal oxide nanoparticles. A comparative study has been conducted herein to investigate differences in the toxic effects caused by these nanoparticles towards the two algae species. The three different concentrations of P25 TiO2 NPs (0.01, 0.1 &amp; 1 μg/mL, i.e., 0.12, 1.25 and 12.52 μM) were selected to correlate surface water concentrations of the nanoparticles, and filtered and sterilized fresh water medium was used throughout this study. There was significant increase (p &lt; 0.001) in hydrodynamic diameter of nanoparticles with respect to both, time (0, 24, 48 and 72 h) as well as concentration under all the exposure conditions. Although, significant dose-dependent morphological (surface area &amp; biovolume) interspecies variations were not observed, it was evident at the highest concentration of exposure within individuals. At 1 μg/mL exposure concentration, a significant difference in toxicity was noted between Chlorella and Scenedesmus under only visible light (p &lt; 0.001) and UVA (p &lt; 0.01) irradiation conditions. The viability data were well supported by the results obtained for oxidative stress induced by NPs on the cells. At the highest exposure concentration, superoxide dismutase and reduced glutathione activities were assessed for both the algae under all the irradiation conditions. Increased catalase activity and LPO release complemented the cytotoxic effects observed. Significant interspecies variations were noted for these parameters under UVA and visible light exposed cells of Chlorella and Scenedesmus species, which could easily be correlated with the uptake of the NPs. © 2016 Elsevier B.V.

Aquatic Toxicology

Differential effects of P25 TiO2 nanoparticles on freshwater green microalgae: Chlorella and Scenedesmus species

Abstract The aim of the current study was to explore the different modes of the cytotoxicity effects of titania nanoparticles (TiO2 NPs) towards the dominant waste water isolate Exiguobacterium acetylicum at an exposure dose of ≤1 μg/mL in the sterilized and filtered waste water already containing 0.770 ± 0.02 μg/mL dissolved Ti4+ ions, under different conditions (UVA, Visible Light and Dark). The aggregation behaviour of TiO2 NPs in the experimental matrix was studied for 0.25, 0.5 and 1 μg/mL concentrations at different time intervals (0, 6 and 12 h). The reduction in cell viability under UVA was significantly more than that of other two conditions, i.e., dark and visible light. At 1 μg/mL of titania NPs for an exposure period of 6 h the cell viability with respect to control was found to be as follows: UVA (11.1 ± 0.33%) &lt;visible light (83.8 ± 1.3%) &lt;dark (84 ± 1.3%). The generation of oxidative stress (hydroxyl and superoxide radicals) was more in the bacterial cells exposed to UVA condition as compared to the cells exposed to visible light and dark condition. A significant increase in the membrane permeability was noted under UVA conditions in comparison to that in dark and visible light conditions. The fluorescence microscopy confirmed cell damage due to exposure to the nanoparticles. The scanning electron microscopy (SEM) analysis demonstrated the morphological distortion in the nanoparticle treated bacterial cells. The adsorption and further internalization of nanoparticles were confirmed by transmission electron microscopy (TEM) and elemental analysis. © 2015 Elsevier Ltd.

Cytotoxicity of titania nanoparticles towards waste water isolate Exiguobacterium acetylicum under UVA, visible light and dark conditions

Indigenous isolates from the waters of chromite mining sites at Sukinda Valley, Orissa, India, showed a considerable enhancement in Cr (VI) bioreduction rate through adaptation and consortia development. On the basis of 16S-rRNA sequencing, these isolates were identified as Bacillus subtilis VITSUKMW1, Acinetobacter junii VITSUKMW2, and Escherichia coli VITSUKMW3. The native isolates showed a high tolerance at 500-1000 mg L-1 of Cr (VI). An increase in the reduction rate from 0.199-0.477 mg L-1 h-1 to 0.5-1.16 mg L-1 h-1 at 5-20 mg L -1 of initial Cr (VI) concentration was achieved by the adapted isolates. An increase in the growth rate and Cr (VI) reduction rate [0.86-2.6813 mg L-1 h-1 at 5-100 mg L-1 of initial Cr (VI) concentration] was observed in the ternary consortium of adapted isolates. The FT-IR spectra revealed the active participation of the bacterial surface groups in the reduction. The development of sequential processes (native → adapted → consortia) employing Cr (VI) tolerant isolates, proves to be a potential bioremediation strategy for specific chromite mine sites.

Industrial & Engineering Chemistry Research

Hexavalent Chromium Bioremoval through Adaptation and Consortia Development from Sukinda Chromite Mine Isolates

PLoS ONE

Listeria monocytogenes Behaviour in Presence of Non-UV-Irradiated Titanium Dioxide Nanoparticles

BioMed Research International

Oxidative Stress Induces Endothelial Cell Senescence via Downregulation of Sirt6

Journal of Colloid and Interface Science

Exopolysaccharides protect Synechocystis against the deleterious effects of Titanium dioxide nanoparticles in natural and artificial waters

Decreased Phototoxic Effects of TiO₂ Nanoparticles in Consortium of Bacterial Isolates from Domestic Waste Water

Journal	PLOS ONE
Publisher	Public Library of Science (PLoS)
ISSN	19326203
Open Access	Yes