Effect Of Usual Chemical Pesticides And Antibiotics On Bacillus Thuringiensis

As one of important branch of micro-pesticide. Bacillus thuringiensis (Bt) are widely used in controlling pests on agriculture , forest , sanitation and so on. And notable effects in economic society and zoology were obtained. In micro-controlling, B1 has showed its unsubstitute state. On the basis of microbiology, the research work is on the problems about conservation and. application of preparation of Bt. The effects of chemistry pesticides when blended with Bt and antibiotics as antisepsis on spore and parasporal crystal of Bt were studied.The effects of 9 kinds of 4 species (pyrethroid compounds, organic phosporus compounds, carbamate compounds and killing-mite compounds) of chemical pesticides on spore and parasporal crystal of CH strain of Bacillus thuringiensis were studied when the two kind of pesticides were blended to control pests. The results of the present study showed that these chemical insecticides had different effects on Bt spore and insecticidal crystal protein (ICP). The analysis of SDS-PAGE showed that pyrethroid compounds and organic phosporus compounds could do good to ICP of Bt. Dichlorvos was very harmful to parasporal crystals. The reason of the latter may be: (1)the P=O configuration of the efficient content of dichlorvos may oxygenize ICP so that the activity of ICP was destroyed: (2)some reducing agent in the dichlorvos preparation would do great harm to ICP. Methomyl, dicofol and pyridaben hadn't obvious effects on ICP. Among the nine insecticides studied, deltamethrin. chlorpyrifos. dicofol and pyridaben had no harmful effects and they may be mixed with Bt as composite preparation; Beta-cypermethrin. cyhalothrin. methomyl and phoxim may be temporarily mixed with Bt for use. Dichlorvos can't be mixed with Bt as composite preparation or temporarily mixed with Bt for use.On the contagion of preparation and the decrease of toxin in Suspension Concentrate (SC), fourteen kinds of medical antibiotics were studied about their effects on prohibiting the revegetation of spores and parasporal crystals as antisepsis. Theresults showed that these antibiotics had different effects on Bt spore and ICP. The optimal antibiotics for controlling spore revegetation were ncrythromycin and ciprofloxacin hydrochloride, both at 0.5 u g/ml. Oflixacin and ofloxacin needed higher doses, at 5 u g/ml in liquid which could control spores growth for 96h. The others were above 30 u g/ml to take effect. The spores treated with these antibiotics could bourgeon when the antibiotic was diluted or eliminated. SDS-PAGE and bioassay showed that Oflixacin , erythromycin , ofloxacin and ciprofloxacin hydrochloride did not destroyed parasporal crystal. Ofloxacin had better preservation among the four antibiotics. After the fermented liquid added with ofloxacin was stored at 45℃ for four days, the percent of the original activity remained was 96.2%. According to the laboratory research, the author thought that some kinds of antibiotics could prohibit the growth of spore and some other saprophyte when antibiotic was used as antisepsis in SC. Thus, some antibiotics can replace chemical-synthesizing antisepsis which may contaminate air, water in great extent. Meanwhile. these antibiotics can also retain the stabilization of SC better.