Comprehensive understanding the impacts of dietary exposure to polyethylene microplastics on genetically improved farmed tilapia (Oreochromis niloticus): tracking from growth, microbiota, metabolism to gene expressions.

Microplastics (MPs) pollution has been recognized as a threat to sustainable fisheries due to the risks of MPs contamination in the process of feed production and susceptibility of fish to ingest MPs from the aquatic environment. In this study, we applied comprehensive approaches to investigate the impacts of polyethylene microplastics (PE-MPs) on juvenile genetically improved farmed tilapia (GIFT, Oreochromis niloticus) through 9-week dietary exposure based on growth performance, gut microbiota, liver metabolism, and gene expressions in brain and liver tissues. Dietary exposure to two kinds of PE-MPs with different median size (27 µm and 63 µm, respectively) concentration-dependently decreased weight gain (WG), while increased feed conversion ratio (FCR) and hepatosomatic index (HSI) of the tilapia. Dietary administration of PE-MPs also significantly reduced the activities of intestinal protease and amylase. PE-MPs particles of the larger size groups (63 µm) were mainly detected in feces, but those of the smaller ones (27 µm) tended to be accumulated in intestine. PE-MPs ingestion resulted in the alteration of gut microbiota composition, with Fusobacteria, Verrucomicrobia and Firmicutes as the overrepresented bacterial taxa. Metabolomic assays of liver samples in fish fed the diets containing 8 % of PE-MPs revealed the particle size-specific variations in composition of differential metabolites and metabolism pathways such as amino acid and glycerophospholipid metabolism. Gene expressions of brain and liver samples were analyzed by RNA-seq. Photoperiodism and circadian rhythm were the representative biological processes enriched for the differentially expressed genes (DEGs) identified from the brain. Citrate cycle (TCA cycle) was the most enriched pathway revealed by a joint transcriptomic and metabolic pathway analysis for the liver, followed by propanoate and pyruvate metabolism. Furthermore, an integration analysis of the gut microbiome and liver transcriptome data identified significant associations between several pathogenic bacteria taxa and immune pathways. Our findings demonstrated that the sizes and concentrations of PE-MPs are critically related to their toxic impacts on microbiota community, metabolism, gene expressions and thus fish growth.

Elevated atmospheric CO2 might increase the health risk of long-term ingestion of leafy vegetables cultivated in residual DDT polluted soil.

Residual dichlorodiphenyltrichloroethane (DDT) in the environment and a continuously increasing atmospheric carbon dioxide (CO2) concentration are two issues that have received a lot of attention. This study was conducted using a pot experiment to investigate the interactive effects of elevated CO2 and DDT on the uptake of DDT, the physiological responses and the resulting health risks in three vegetables. These vegetables included Brassica juncea var. foliosa Bailey (B. Bailey), Brassica campestris L. var. communis Tsen et Lee Suzhou Qing (B. Lee) and Brassica campestris L. ssp. pekinensis (Lour.) Olsson Chun Dawang (B. Olsson). Two levels of CO2 and four DDT treatment levels were set up. Results showed 5 mg kg-1 DDT significantly reduced the shoot biomass of B. Bailey when compared to 0 mg kg-1 DDT treatment under ambient CO2 condition. Elevated CO2 concentration stimulated the growth of B. Bailey and B. Lee, increased the DDT uptake in the shoots of both vegetables and the values of some photosynthesis indices, and triggered the activity of peroxidase and catalase in the shoots when compared to the related ambient CO2 treatment. Elevated CO2 concentration increased the values of hazard indexes for non-carcinogenic and cancer risks of all vegetables when compared to the individual ambient CO2 treatment (each of vegetable has an ambient CO2 treatment), especially for B. Bailey (increase amplitude of 123.81%-127.78% at 5 mg kg-1 DDT). Long-term ingestion with these DDT-polluted vegetables might result in an elevated carcinogenic risk and elevated atmospheric CO2 may enhance the non-carcinogenic and carcinogenic risks.

Burkholderia metalliresistens sp. nov., a multiple metal-resistant and phosphate-solubilising species isolated from heavy metal-polluted soil in Southeast China.

A metal-resistant and phosphate-solubilising bacterium, designated as strain D414(T), was isolated from heavy metal (Pb, Cd, Cu and Zn)-polluted paddy soils at the surrounding area of Dabao Mountain Mine in Southeast China. The minimum inhibitory concentrations of heavy metals for strain D414(T) were 2000 mg L(-1) (Cd), 800 mg L(-1) (Pb), 150 mg L(-1) (Cu) and 2500 mg L(-1) (Zn). The strain possessed plant growth-promoting properties, such as 1-aminocyclopropane-1-carboxylate assimilation, indole production and phosphate solubilisation. Analysis of 16S rRNA gene sequence indicated that the isolate is a member of the genus Burkholderia where strain D414(T) formed a distinct phyletic line with validly described Burkholderia species. Strain D414(T) is closely related to Burkholderia tropica DSM 15359(T), B. bannensis NBRC E25(T) and B. unamae DSM 17197(T), with 98.5, 98.3 and 98.3 % sequence similarities, respectively. Furthermore, less than 34 % DNA-DNA relatedness was detected between strain D414(T) and the type strains of the phylogenetically closest species of Burkholderia. The dominant fatty acids of strain D414(T) were C14:0, C16:0, C17:0 cyclo and C18:1 ω7c. The DNA G+C content was 62.3 ± 0.5 mol%. On the basis of genotypic, phenotypic and phylogenetic data, strain D414(T) represents a novel species, for which the name Burkholderia metalliresistens sp. nov. is proposed, with D414(T) (=CICC 10561(T) = DSM 26823(T)) as the type strain.

[Effects of intercropping different crops with maize on the Cd uptake by maize].

A greenhouse experiment was conducted to investigate the effects of intercropping 7 kinds of crops on the Cd uptake by maize (Zea mays L.). The results showed that most intercrops had no significant effects on the growth of maize, only with purple haricot reduced the maize biomass by 32.2% of the control. Legume crops enhanced the total quantity of Cd in maize in a great magnitude, and chickpea worked most efficiently, which doubled the Cd quantity in maize. The 7 intercrops showed different capability of Cd uptake, among which, rape and amaranth absorbed larger amount of Cd, with a Cd level of 53.9 mg x kg(-1) and 51.0 mg x kg(-1) in their aboveground parts, respectively, and of 91.8 mg x kg(-1) in amaranth root when the soil Cd content was 3 mg x kg(-1) soil. There was an interaction between maize and intercrops in Cd uptake. Legumes absorbed smaller amount of Cd but significantly increased the Cd uptake by maize, while amaranth was in adverse. Rape had a higher level of Cd concentration in its shoot, but reduced the Cd in aboveground part of maize. It was indicated that if maize was used for phytoremediation of Cd-contaminated soil, a higher efficiency of Cd removal could be achieved by intercropping it with legumes. Rape and amaranth could be the two promising plants for phytoremediation because of their high Cd accumulation.

Effect of fertilizer and water content on N2O emission from three plantation soils in south China.

The effects of fertilizers and water content on N2O emission were studied using the three most typical plantation soils. Soil incubations were performed and fertilization and water content treatments were designed. At 25% of saturated water content(SWC), N2O emissions from the soil treated with urea, KNO3, (NH4)2 SO4 and KH2 PO4 were compared at application rates of 0, 100, 200, 300 and 500 kg/hm2. At 80% of SWC, similar experiments were carried out but at only one application rate(500 kg/hm2). N2O emissions at various water contents(20%, 35%, 50%, 65%, 80% and 100% of SWC) were studied. At low water content(25% of SWC), neither nitrogen nor phosphorus(or potassium) fertilizers led to a high level of N2O emission, which generally ranged from 2.03 to 29.02 microg/(m2 x h). However, at high water content(80% SWC), the fertilizers resulted in much greater N2O emission irregardless of soil tested. The highest N2O emission rates after 24 h of water addition were 1233 microg/(m2 x h) for S. superba soil, 1507 microg/(m2 x h) for P. elliottii soil and 1869 microg/ (m2 x h) for A. mangium soil respectively. N2O emission from soils treated with urea, (NH4)2 SO4 and KH2 PO4 immediately dropped to a low level but steadily increased to a very high level for the soil treated with KNO3. High NO3- content was a basis of high level of N2O emission. N2O emission rates from soils peaked shortly after flooding, rapidly dropping to a very low level in soil from non-legume plantations, but lasting for a relatively long period in soil from legume plantations. When soil water content increased equaling to or higher than 65%, the accumulated N2O emission over a period of 13 d ranged from 20.21-29.78 mg/m2 for S. superba, 30.57-70.12 mg/m2 for P. elliottii and 300.89-430.51 mg/m2 for A. mangium. The critical water content was 50% of SWC, above which a high level of N2O emission could be expected, and below which very little N2O emissions were detected. The results suggest that, at low water content (< 50% of SWC), the fertilization practice is safe with regard to N2O emissions, but at high water content (> 50% of SWC), nitrogen fertilizer in the form of nitrate could yield a 100-fold increase in N2O emissions. Legume plantations like A. mangium should be avoided in low lands which could easily suffer from flooding or poor drainage.