Youchao Zhu

A comparison of the effects of copper nanoparticles and copper sulfate on Phaeodactylum tricornutum physiology and transcription

Copper nanoparticles (CuNPs) have been used in a broad range of applications. However, they are inevitably released into the marine environment, making it necessary to evaluate their potential effects on marine phytoplankton. In this study, the short-term (96h) effects of CuNPs and CuSO4 on Phacodactylum tricornutum growth, photosynthesis, reactive oxygen species production and transcription were assessed. It was found that high concentrations (40μM) of CuNPs and CuSO4 significantly inhibited the growth, photosynthesis and induced oxidative stress of P. tricornutum, while lower concentrations caused a hormetic response as indicated by a slight stimulation in algal growth. The high percentage of dissolved Cu (78-100%) in culture medium suggested that the dissolved Cu was the main driver of toxicity during CuNPs treatment. The algal cells upregulated electron transport chain-related genes to produce more energy and restore photosynthesis after 96h of treatment with CuNPs and CuSO4. This study delineates the cellular mechanism behind the toxicity of CuNPs and CuSO4 on marine diatoms.

Physiological and Molecular Response of Arabidopsis thaliana to CuO Nanoparticle (nCuO) Exposure

The widespread application of copper oxide nanoparticles (nCuO) results in ecological risk when nanoparticles enter the environment. This study clarifies the mechanism of nCuO toxicity in Arabidopsis thaliana seedlings via comparison with copper (Cu) ion bioeffects. Under the same culture conditions, Cu2+ ion exposure exerted a stronger inhibitory effect on plant fresh weight and growth and caused stronger oxidative disruption (measured by malondialdehyde, MDA) than nCuO exposure. The Cu2+ ions also showed a stronger induction effect than did nCuO on the activity of antioxidant enzymes and the transcription of antioxidant-related genes. Dissolved Cu2+ ions contributed a minority of the toxicity of nCuO, implying that nCuO itself showed relative strong phytotoxicity. The work presented here will help increase our understanding of the toxicity of metal nanoparticles in plants.

Interacting effect of diclofop-methyl on the rice rhizosphere microbiome and denitrification

A better knowledge of the intertwined effects of herbicides on plant physiology and microbiome as well as nutrient biogeochemical cycles are needed for environmental management. Here we studied the influence of herbicide diclofop-methyl (DM) on the rice root microbiome and its relationship with N cycle. To do so, we exposed rice seedlings to 100 μg/L DM and studied rhizosphere microbiota using MiSeq-pyrosequencing, root exudation by GC-MS, and denitrification activity by 15N isotope-tracing and qRT-PCR. The richness and diversity of rhizosphere microorganisms, significantly increased after DM exposure combined with an increase in root exudation of amino acids, sugars, and fatty acids. Transcription of denitrification-related gene and denitrification rate increased significantly in the rice rhizosphere. Our results suggest that DM strongly influenced the root exudation of bacteria nutrients, which affected root microbiome community and potentially influenced N cycle in rice rhizosphere.

Investigation of Rhizospheric Microbial Communities in Wheat, Barley, and Two Rice Varieties at the Seedling Stage.

The plant rhizosphere microbiota plays multiple roles in plant growth. We investigated the taxonomic and functional variations in the rhizosphere microbial community, examining both prokaryotes and eukaryotes, of four crops at the seedling stage: wheat, barley, and two rice varieties ( indica and japonica) seeded in paddy soil. The diversity of rhizosphere communities in these four species was determined. Results showed that wheat and barley had much stronger selection effects than rice for the rhizosphere microbial community. Functional metagenomic profiling indicated that a series of sequences related to glycan, limonene, and pinene degradation pathways as well as some relatively rare functions related to N or S metabolism were enriched in the rhizosphere soil. We conclude that the four tested crops induced the formation of the microbial community with specific features that may influence the plant growth but stochastic processes also appreciably influenced the functional selection.

Changes in bacterial community structure and antibiotic resistance genes in soil in the vicinity of a pharmaceutical factory.

China is the largest global producer of antibiotics. With the demand for antibiotics increasing every year, it is necessary to assess potential environmental risks and the spread of antibiotic resistance genes (ARGs) associated with antibiotic production. Here, we investigated the occurrence and distribution of ARGs in soil in the vicinity of a pharmaceutical factory. The results showed that antibiotic concentrations were under the detection limit; however, ARGs were present in soil and tended to be enriched near the factory. A significant correlation between the relative abundance of intI-1 and tetracycline ARGs implied that horizontal gene transfer might play an important role in the spread of ARGs. The occurrence of these ARGs could be the results of previous antibiotic contamination. However, the soil bacterial community structure seemed to be more affected by nutrients or other factors than by antibiotics. Overall, this study supports the viewpoint that long-term pharmaceutical activity might have a negative effect on environmental health, thus, underscoring the need to regulate antibiotic production and management.