Maintaining stable water quality is one of the key processes for recirculating coral aquaculture. Traditional aquarium systems which mainly utilized a nitrification of nitrifying bacteria attached to the surface of ma...Maintaining stable water quality is one of the key processes for recirculating coral aquaculture. Traditional aquarium systems which mainly utilized a nitrification of nitrifying bacteria attached to the surface of massive artificial filter material are difficult to maintain the oligotrophic conditions necessary for coral aquaculture. This study investigated the removal effects of dissolved inorganic nitrogen(ammonia and nitrate) by live rock(LR), a key component in the "Berlin system" coral aquarium. The expression levels of bacterial functional genes, AOA3,amo A and nos Z, were measured on the exterior and interior of LR. The nitrifying and denitrifying bacterial abundance on LR was quantified and the nitrogen nutrient regulatory effects of LR were evaluated. The results demonstrated that LR mainly removed ammonium(NH_4^+) from the water with a mean efficiency of 0.141 mg/(kg·h), while the removal of nitrate(NO_3~–) was not significant. Bacterial diversity analysis showed that ammonia-oxidizing bacteria(AOB) were the most common bacteria on LR, which accounted for 0.5%–1.4% of the total bacterial population, followed by denitrifying bacteria, which accounted for 0.2% of the total population, and the ammonia-oxidizing archaea(AOA) were the least common type(<0.01%). The low abundance of denitrifying bacteria may be responsible for the poor nitrate(NO_3~–) removal of LR. Thus, other biological filtration methods are needed in coral aquaria to control nitrates generated from nitrification or biological metabolism.展开更多
LRP6,a co-receptor for the morphogen Wnt,aids endocytosis of anthrax complexes.Here we report that Dickkopf1(DKK1)protein,a secreted LRP6 ligand and antagonist,is also a modulator of anthrax toxin sensitivity.shRNA-me...LRP6,a co-receptor for the morphogen Wnt,aids endocytosis of anthrax complexes.Here we report that Dickkopf1(DKK1)protein,a secreted LRP6 ligand and antagonist,is also a modulator of anthrax toxin sensitivity.shRNA-mediated gene silencing or TALEN-mediated gene knockout of DKK1 reduced sensitivity of cells to PA-dependent hybrid toxins.However,unlike the solely inhibitory effect on Wnt signaling,the effects of DKK1 overexpression on anthrax toxicity were bidirectional,depending on its endogenous expression and cell context.Fluorescence microscopy and biochemical analyses showed that DKK1 facilitates internalization of anthrax toxins and their receptors,an event mediated by DKK1-LRP6-Kremen2 complex.Monoclonal antibodies against DKK1 provided dose-dependent protection to macrophages from killing by anthrax lethal toxin(LT).Our discovery that DKK1 forms ternary structure with LRP6 and Kremen2 in promoting PA-mediated toxin internalization provides a paradigm for bacterial exploitation of mechanisms that host cells use to internalize signaling proteins.展开更多
基金The Regional Demonstration of Marine Economy Innovative Development Project under contract No.16PZY002SF18the Xiamen Southern Ocean Research Center Project under contract No.14CZY037HJ11+1 种基金the Guangxi Natural Science Foundation under contract No.2016GXNSFBA380228the China-ASEAN Maritime Cooperation Fund Project under contract No.HX150702
文摘Maintaining stable water quality is one of the key processes for recirculating coral aquaculture. Traditional aquarium systems which mainly utilized a nitrification of nitrifying bacteria attached to the surface of massive artificial filter material are difficult to maintain the oligotrophic conditions necessary for coral aquaculture. This study investigated the removal effects of dissolved inorganic nitrogen(ammonia and nitrate) by live rock(LR), a key component in the "Berlin system" coral aquarium. The expression levels of bacterial functional genes, AOA3,amo A and nos Z, were measured on the exterior and interior of LR. The nitrifying and denitrifying bacterial abundance on LR was quantified and the nitrogen nutrient regulatory effects of LR were evaluated. The results demonstrated that LR mainly removed ammonium(NH_4^+) from the water with a mean efficiency of 0.141 mg/(kg·h), while the removal of nitrate(NO_3~–) was not significant. Bacterial diversity analysis showed that ammonia-oxidizing bacteria(AOB) were the most common bacteria on LR, which accounted for 0.5%–1.4% of the total bacterial population, followed by denitrifying bacteria, which accounted for 0.2% of the total population, and the ammonia-oxidizing archaea(AOA) were the least common type(<0.01%). The low abundance of denitrifying bacteria may be responsible for the poor nitrate(NO_3~–) removal of LR. Thus, other biological filtration methods are needed in coral aquaria to control nitrates generated from nitrification or biological metabolism.
基金supported in part by the National Natural Science Foundation of China(30770465,31070115)the National Basic Research Program of China(2010CB911800)+1 种基金the Peking-Tsinghua Center for Life Sciences(to WenSheng Wei)by an award(HDTRA1-06-C-0039)from the US Defense Threat Reduction Agency(to Stanley N.Cohen)
文摘LRP6,a co-receptor for the morphogen Wnt,aids endocytosis of anthrax complexes.Here we report that Dickkopf1(DKK1)protein,a secreted LRP6 ligand and antagonist,is also a modulator of anthrax toxin sensitivity.shRNA-mediated gene silencing or TALEN-mediated gene knockout of DKK1 reduced sensitivity of cells to PA-dependent hybrid toxins.However,unlike the solely inhibitory effect on Wnt signaling,the effects of DKK1 overexpression on anthrax toxicity were bidirectional,depending on its endogenous expression and cell context.Fluorescence microscopy and biochemical analyses showed that DKK1 facilitates internalization of anthrax toxins and their receptors,an event mediated by DKK1-LRP6-Kremen2 complex.Monoclonal antibodies against DKK1 provided dose-dependent protection to macrophages from killing by anthrax lethal toxin(LT).Our discovery that DKK1 forms ternary structure with LRP6 and Kremen2 in promoting PA-mediated toxin internalization provides a paradigm for bacterial exploitation of mechanisms that host cells use to internalize signaling proteins.
