Organic carbon availability limiting microbial denitrification in the deep vadose zone

Microbes in the deep vadose zone play an essential role in the mitigation of nitrate leaching; however, limited information is available on the mechanisms of microbial denitrification due to sampling difficulties. We experimentally studied the factors that affect denitrification in soils collected down to 10.5 meters deep along the soil profile. After an anoxic pre-incubation, denitrification rates moderately increased and the N₂ O/(N₂ O + N₂ ) ratios declined while the microbial abundance and diversity did not change significantly in most of the layers. Denitrification rate was significantly enhanced and the abundance of the denitrification genes was simultaneously elevated by the increased availability of organic carbon in all studied layers, to a greater extent in the subsurface layers than in the surface layers, suggesting the severe scarcity of carbon in the deep vadose zone. The genera Pseudomonas and Bacillus, which are made up of a number of species that have been previously identified as denitrifiers in soil, were the major taxa that respond to carbon addition. Overall, our results suggested that the limited denitrification in the deep vadose zone is not because of the lack of denitrifiers, but due to the low abundance of denitrifiers which is caused by low carbon availability.

Abstract P4-07-11: MicroRNA-367a promotes tumor growth and stemness potential by targeting FBXW7 in breast cancer

Increasing studies showed that MicroRNAs (miRNAs)participate in the carcinogenesis and progression of breast cancer, but the specific mechanism of miRNAs in breast cancer needs to be furtherexplored. in this study, wefound that miR-367a was significantly up-regulated in breast cancer tissue samples and cell lines, compared to paired normal tumor-adjacent samples and MCF-10A. meanwhile, Kaplan–Meier analysis demonstrated high miR-367a expression was evidently correlated with poor prognostic features of breast cancer. overexpression of miR-367a remarkably promoted proliferation, cell cycle,inhibited apoptosis ratios and stem-like capacity of breast cancer cells in vitro, whilesilencing the expression of miR-367a dramaticallyreversed these cellular events .in addition,In vivo studies showed that knockdown of miR-367a inhibited tumor growth of breast cancer ,moreover, F-box and WD repeat domain-containing 7 (FBXW7) was identified as a direct target genes of miR-367a, as miR-367a directly bound to the 3'untranslated region of FBXW7 . Notably, alterations of FBXW7 levels abrogated the effects of miR-367a on breast cancer cell proliferation, cell cycle, apoptosis and stemness potential. In conclusion,evidence from this study demonstrated that miR-367amay serve as a novel prognostic indicator for breast cancer patients andexerts tumor promotion,at least in part, by inhibiting FBXW7.

Key words: miR-367a, FBXW7, breast cancer, tumor growth, stem-like capacity.

Citation Format: Xiao G, Zhang J, Sun X, Qin S, Zhang B, Liu D, Liu J, Ren H. MicroRNA-367a promotes tumor growth and stemness potential by targeting FBXW7 in breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-07-11.

Perturbation-free measurement of in situ di-nitrogen emissions from denitrification in nitrate-rich aquatic ecosystems

Increased production of reactive nitrogen (Nr) from atmospheric di-nitrogen (N₂) has greatly contributed to increased food production. However, enriching the biosphere with Nr has also caused a series of negative effects on global ecosystems, especially aquatic ecosystems. The main pathway converting Nr back into the atmospheric N₂ pool is the last step in the denitrification process. Despite several attempts, there is still a need for perturbation-free methods for measuring in situ N₂ fluxes from denitrification in aquatic ecosystems at the field scale. Such a method is needed to comprehensively quantify the N₂ fluxes from aquatic ecosystems. Here we observed linear relationships between the δ¹⁵N-N₂O signatures and the logarithmically transformed N₂O/(N₂+N₂O) emission ratios. Through independent measurements, we verified that the perturbation-free N₂ flux from denitrification in nitrate-rich aquatic ecosystems can be inferred from these linear relationships. Our method allowed the determination of field-scale in situ N₂ fluxes from nitrate-rich aquatic ecosystems both with and without overlaying water. The perturbation-free in situ N₂ fluxes observed by the new method were almost one order of magnitude higher than those by the sediment core method. The ability of aquatic ecosystems to remove Nr may previously have been severely underestimated.

Influence of dietary rapeseed meal levels on growth performance, organ health and standardized ileal amino acid digestibility in meat ducks from 15 to 35 days of age

This study was conducted to investigate the effects of dietary rapeseed meal (RSM) inclusion levels on growth performance, organ health and standardized ileal amino acid digestibility (SIAAD) in meat ducks from 15 to 35 days of age. Six hundred and eighty 15-days-old ducks were randomly allotted to five treatments based on body weight. Five isonitrogenous and isoenergetic diets were formulated on a digestible amino acid basis by replacing 0% (the control), 25%, 50%, 75% and 100% (based on fresh) of protein from soya bean meal (SBM) with protein from RSM. The corresponding levels of RSM in experimental diets were 0%, 6.66%, 13.32%, 19.98% and 26.64% respectively. With increasing dietary RSM levels, body weight (BW) and average daily gain (ADG) linearly decreased (p < 0.001), whereas feed-to-gain ratio (F: G) linearly increased (p = 0.0078). Ducks fed the diets with 13.32% or more RSM had significantly lower (p < 0.05) BW, ADG and ADFI, or higher F: G than ducks fed the control diet. The maximum limit of dietary RSM supplementation was estimated to range from 4.27% to maximize ADG for 15 to 35 days to 11.69% to maintain feed intake for 15 to 35 days on the basis of a broken-line model. At day35, the 4th primary wing feather length and SIAAD (except for Met, Thr and Val) linearly decreased (p < 0.001), and the thyroid glands weight (% of BW) linearly increased (p < 0.05) with increasing dietary RSM levels. Ducks fed the RSM inclusion diets had significantly lower (p < 0.0001) serum aspartate aminotransferase (AST) and alanine transaminase (ALT) activities than ducks fed the control diet. These results suggested that the maximum limit of dietary RSM containing 7.57 μmol/g glucosinolates was estimated to be 4.27% to avoid growth reduction.