Evidence that nano-TiO2 induces acute cytotoxicity to the agronomically beneficial nitrogen fixing bacteria Sinorhizobium meliloti

2021 ◽  
Author(s):  
Jieping Wang ◽  
Yu Jia ◽  
Joann K. Whalen ◽  
Heather McShane ◽  
Brian T. Driscoll ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Sinorhizobium Meliloti ◽  
Ultra Violet ◽  
Oxygen Species ◽  
Light Conditions ◽  
Nitrogen Fixing ◽  
Nano Tio2 ◽  
Aqueous Dispersions ◽  
Acute Cytotoxicity ◽  
Meliloti Strain

When nano-sized titanium dioxide (nano-TiO2) absorbs ultra-violet (UV-A) radiation, it produces reactive oxygen species that can be toxic to bacteria. We used the agronomically beneficial nitrogen-fixing bacterium Sinorhizobium meliloti strain 1021 as a model microorganism to detect nano-TiO2 toxicity. S. meliloti was exposed to aqueous dispersions of micrometer-sized TiO2 (micron-TiO2, 44 μm) or nanometer-sized TiO2 (nano-TiO2, 21 nm) at nominal concentrations of 0, 100, 300, 600, 900 and 1800 mg TiO2/L. There were fewer viable S. meliloti after exposure to nano-TiO2 under dark and UV-A light conditions. Nano-TiO2 was more toxic to S. meliloti with UV-A irradiation (100% mortality at 100 mg TiO2/L) than under dark conditions (100% mortality at 900 mg TiO2/L). Micron-TiO2 concentrations less than 300 mg TiO2/L had no effect on the S. meliloti viability under dark or UV-A light conditions. Exposure to 600 mg/L or more of micron-TiO2 under UV-A light could also photo-kill S. meliloti cells (100% mortality). Further study is needed to ascertain whether nano-TiO2 interferes with the growth of N2-fixing microorganisms in realistic agricultural environments.

scholarly journals Rapid evaluation of oxygen vacancies-enhanced photogeneration of the superoxide radical in nano-TiO2 suspensions

RSC Advances ◽  
2020 ◽  
Vol 10 (49) ◽  
pp. 29082-29089
Author(s):  
Wanchao Yu ◽  
Fengjie Chen ◽  
Yarui Wang ◽  
Lixia Zhao
Keyword(s):  
Reactive Oxygen Species ◽  
Photocatalytic Degradation ◽  
Oxygen Vacancies ◽  
Superoxide Radical ◽  
Surface Defects ◽  
Reactive Oxygen ◽  
Rapid Evaluation ◽  
Oxygen Species ◽  
Nano Tio2 ◽  
Degradation Of Pollutants

Reactive oxygen species (ROS) play an important role in the photocatalytic degradation of pollutants and are closely related to the surface defects of a semiconductor.

Toxicity of nano-TiO2 on algae and the site of reactive oxygen species production

2015 ◽  
Vol 158 ◽  
pp. 1-13 ◽  
Author(s):  
Fengmin Li ◽  
Zhi Liang ◽  
Xiang Zheng ◽  
Wei Zhao ◽  
Miao Wu ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Reactive Oxygen Species Production ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Nano Tio2 ◽  
Species Production

scholarly journals Effects of Aqueous Dispersions of C60, C70 and Gd@C82 Fullerenes on Genes Involved in Oxidative Stress and Anti-Inflammatory Pathways

2021 ◽  
Vol 22 (11) ◽  
pp. 6130
Author(s):  
Elena V. Proskurnina ◽  
Ivan V. Mikheev ◽  
Ekaterina A. Savinova ◽  
Elizaveta S. Ershova ◽  
Natalia N. Veiko ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Reactive Oxygen Species ◽  
Inflammatory Responses ◽  
Reactive Oxygen ◽  
Fetal Lung ◽  
Lung Fibroblasts ◽  
Heme Oxygenase 1 ◽  
Oxygen Species ◽  
Aqueous Dispersions ◽  
Anti Inflammatory

Background: Fullerenes and metallofullerenes can be considered promising nanopharmaceuticals themselves and as a basis for chemical modification. As reactive oxygen species homeostasis plays a vital role in cells, the study of their effect on genes involved in oxidative stress and anti-inflammatory responses are of particular importance. Methods: Human fetal lung fibroblasts were incubated with aqueous dispersions of C60, C70, and Gd@C82 in concentrations of 5 nM and 1.5 µM for 1, 3, 24, and 72 h. Cell viability, intracellular ROS, NOX4, NFκB, PRAR-γ, NRF2, heme oxygenase 1, and NAD(P)H quinone dehydrogenase 1 expression have been studied. Results & conclusion: The aqueous dispersions of C60, C70, and Gd@C82 fullerenes are active participants in reactive oxygen species (ROS) homeostasis. Low and high concentrations of aqueous fullerene dispersions (AFD) have similar effects. C70 was the most inert substance, C60 was the most active substance. All AFDs have both “prooxidant” and “antioxidant” effects but with a different balance. Gd@C82 was a substance with more pronounced antioxidant and anti-inflammatory properties, while C70 had more pronounced “prooxidant” properties.

scholarly journals OxyR-Dependent Transcription Response ofSinorhizobium melilotito Oxidative Stress

2018 ◽  
Vol 200 (7) ◽  
Author(s):  
Alisa P. Lehman ◽  
Sharon R. Long
Keyword(s):  
Oxidative Stress ◽  
Reactive Oxygen Species ◽  
Sigma Factor ◽  
Sinorhizobium Meliloti ◽  
Reactive Oxygen ◽  
Defense Responses ◽  
Complex Life Cycle ◽  
Oxygen Species ◽  
Content Type ◽  
Infection Threads

ABSTRACTReactive oxygen species such as peroxides play an important role in plant development, cell wall maturation, and defense responses. During nodulation with the host plantMedicago sativa,Sinorhizobium meliloticells are exposed to H2O2in infection threads and developing nodules (R. Santos, D. Hérouart, S. Sigaud, D. Touati, and A. Puppo, Mol Plant Microbe Interact 14:86–89, 2001,https://doi.org/10.1094/MPMI.2001.14.1.86).S. meliloticells likely also experience oxidative stress, from both internal and external sources, during life in the soil. Here, we present microarray transcription data forS. melilotiwild-type cells compared to a mutant deficient in the key oxidative regulatory protein OxyR, each in response to H2O2treatment. Several alternative sigma factor genes are upregulated in the response to H2O2; the stress sigma generpoE2shows OxyR-dependent induction by H2O2, whilerpoH1expression is induced by H2O2irrespective of theoxyRgenotype. The activity of the RpoE2 sigma factor in turn causes increased expression of two more sigma factor genes,rpoE5andrpoH2. Strains with deletions ofrpoH1showed improved survival in H2O2as well as increased levels ofoxyRand total catalase expression. These results imply that ΔrpoH1strains are primed to deal with oxidative stress. This work presents a global view ofS. melilotigene expression changes, and of regulation of those changes, in response to H2O2.IMPORTANCELike all aerobic organisms, the symbiotic nitrogen-fixing bacteriumSinorhizobium melilotiexperiences oxidative stress throughout its complex life cycle. This report describes the global transcriptional changes thatS. melilotimakes in response to H2O2and the roles of the OxyR transcriptional regulator and the RpoH1 sigma factor in regulating those changes. By understanding the complex regulatory response ofS. melilotito oxidative stress, we may further understand the role that reactive oxygen species play as both stressors and potential signals during symbiosis.

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