Crude extract of maggots:Antibacterial effects against Escherichia coli,underlying mechanisms,separation and purification

AIM:To investigate the antibacterial effects of a crude extract of maggots against Escherichia coli(E.coli) and the underlying mechanisms,and to separate and purifythe crude extract of maggots to assess the antibacterial effects of the active ingredients in the crude extract.METHODS:Different concentrations of the crude extract of maggots were incubated with E.coli(O157:H7) and cultured.The optical density(OD) was measured at different time points to plot the OD-T curve.The effects of different concentrations of the crude extract on bacterial membrane permeability were determined by fluorescence probe technique.The effects of different concentrations of the crude extract on plasmid DNA replication were determined by agarose gel electrophoresis.DEAE-Sepharose ion exchange chromatography and Sephacryls-200 HR gel filtration chromatography were used to separate and purify the crude extract of maggots.The molecular weight of proteins in the purified crude extract was determined by SDS-PAGD electrophoresis,and its antibacterial effects were determined by turbidimetric method.RESULTS:The antibacterial effects of the crude extract of maggots at concentrations > 0.5 mg/m L were significant.The antibacterial effects of the crude extract at concentrations of 1.0,1.5 and 2.0 mg/m L did not differ significantly.Fluorescence probe analysis showed that the rate of membrane permeability change was 1223.1% in bacteria incubated with 2 mg/m L of the crude extract,and 1300.0% in those incubated with 80 mg/m L of the crude extract.Plasmid DNA was undetectable in E.coli incubated with 2 and 80 mg/m L of the crude extract.A low molecular weight protein band(about 15 k Da) was detected in the crude extract of maggots and eluent,but not in eluant,from DEAE-Sepharose ion exchange chromatography.The antibacterial effects of the crude extract of maggots and eluent were superior to those of eluant,with the antibacterial effects of eluents being better than those of the crude extract of maggots.Of 24 tubes offiltrates,the antibacterial effects of filtrates in tubes 4,5 and 11 were significantly higher than those of the control.The molecular weight of the protein in filtrates in tubes 4,5 and 11 was about 15 k Da.CONCLUSION:The crude extract of maggots exhibits obvious,dose-dependent antibacterial effects.The crude extract exerts antibacterial effects by changing the bacterial membrane permeability and inhibiting plasmid DNA replication.The prote in that has antibacterial effects in the crude extract of maggots has a molecular weight of about 15 k Da.

Will China achieve its 2060 carbon neutral commitment from the provincial perspective?

China has pledged to peak carbon emissions before 2030 and strive to achieve carbon neutrality before 2060.However,the significant variations of provincial carbon emissions make it unclear whether they can jointly fulfill the national carbon peak and neutrality goal.Thus,this study predicts the emission trajectories at provincial level in China by employing the extended STIRPAT(Stochastic Impacts by Regression on Population,Affluence,and Technology)model to see the feasibility and time of reaching peak carbon emissions and carbon neutrality.We found that most provinces can achieve peak emission before 2030 but challenging to achieve carbon neutrality before 2060,even considering the ecological carbon sink.The provincial neutrality time is concentrated between 2058 and 2070;the sooner the carbon emission peaks,the earlier the carbon neutral will be realized.The aggregated carbon emissions at provincial level show that China can achieve its carbon emission peak of 9.64-10.71 Gt before 2030,but it is unlikely to achieve the carbon neutrality goal before 2060 without carbon capture,utilization,and storage(CCUS).With high CCUS development,China is expected to achieve carbon neutrality in 2054-2058,irrespective of the socio-economic scenarios.With low CCUS development,China's carbon neutrality target will be achieved only under the accelerated-improvement scenario,while it will postpone to 2061 and 2064 under the continued-improvement and the business-as-usual scenarios,respectively.