Discovery of cryptolepine derivatives as novel promising agents against phytopathogenic bacteria

To ensure the production of food crops,a series of cryptolepine derivatives were synthesised,after which their antibacterial activities and mechanism of action against three plant pathogens were investigated.Our bioassay results indicated that most of the target compounds displayed potent inhibitory effects against Xanthomonas oryzae(X.oryzae)and Xanthomonas axonopodis pv.citri(X.axonopodis pv.c.).Remarkably,compound 9 exhibited the best in vitro antibacterial activity against X.oryzae,with a minimum inhibitory concentration(MIC)value of 0.78μg·mL^(-1).Compound 2 exhibited the best in vitro antibacterial activity against X.axonopodis pv.c.,with an MIC value of 0.39μg·mL^(-1).These activities were superior to those of copper quinolate(MIC=6.25,25μg·mL^(-1))and thiodiazole copper(MIC=100,200μg·mL^(-1))against X.oryzae and X.axonopodis pv.c.In vivo experiments demonstrated the promising applicability of compound 9 for the control of rice bacterial infections.Furthermore,compound 9 was selected as a candidate to conduct preliminary analyses of the antibacterial mechanisms of cryptolepine derivatives.Scanning electron microscopy and transmission electron microscopy observations,extracellular polysaccharide production,biofilm formation,transcriptomic,quantitative reverse transcription-polymerase chain reaction analyses,and molecular docking assays were performed.Collectively,our findings demonstrated that compound 9 might act via multifarious mechanisms to down-regulate virulence factors and cause cell death.

Underwater glider design based on dynamic model analysis and prototype development

Underwater gliders are efficient mobile sensor platforms that can be deployed for months at a time, traveling thousands of kilometers. Here, we describe our development of a coastal 200 m deep underwater glider, which can serve as an ocean observatory platform operating in the East China Sea. Our glider is developed based on dynamic model analysis: steady flight equilibrium analysis gives the varied range of moving mass location for pitch control and the varied vehicle volume for buoyancy control; a stability analysis is made to discuss the relationship between the stability of glider motion and the location of glider wings and rudder by root locus investigation of glider longitudinal- and lateral-directional dynamics, respectively. There is a tradeoff between glider motion stability and control authority according to the specific glider mission requirements. The theoretical analysis provides guidelines for vehicle design, based on which we present the development progress of the Zhejiang University (ZJU) glider. The mechanical, electrical, and software design of the glider is discussed in detail. The performances of glider key functional modules are validated by pressure tests individually; preliminary pool trials of the ZJU glider are also introduced, indicating that our glider functions well in water and can serve as a sensor platform for ocean sampling.