The effect of antibacterial peptide CM4 of Bombyx mori against E. coll K12 was investigated using scanning electron microscopy(SEM) and transmission electron microscopy (TEM). The ultrastructural changes of E. coli K1...The effect of antibacterial peptide CM4 of Bombyx mori against E. coll K12 was investigated using scanning electron microscopy(SEM) and transmission electron microscopy (TEM). The ultrastructural changes of E. coli K12 were observed by the challenge of the purified antibacterial peptide CM4. The results showed that the antibacterial peptide caused a series of pathological changes on E. coli. SEM and TEM revealed aggregates of bacteria and SEM revealed wrin-kled bacterial surfaces in the early stage. Thereafter, plasmolysis was observed with irregular holes appearing in the two ends of bacteria and the cytoplasmic contents of the cells leaking out. Finally, bacteria became empty vesicles and disintegrated into small fragments subsequently. Comparatively, the bacterial membrane was normal and the bacterial structure remained intact in the control group.展开更多
Comparative genome analysis is performed between Shigella flexneri 2a strain 301 and its close relatives, the nonpathogenic E. Coli K-12 strain MG1655. Result shows that there are 136 DNA segments whose size is larger...Comparative genome analysis is performed between Shigella flexneri 2a strain 301 and its close relatives, the nonpathogenic E. Coli K-12 strain MG1655. Result shows that there are 136 DNA segments whose size is larger than 1000 bp absent from Shigella flexneri 2a strain 301, which is up to 717253 bp in total length. These deleted segments altogether contain 670 open reading frames (ORFs). Prediction of these ORFs indicates that there are 40% genes of unknown function. The other genes of definite functions encode metabolic enzymes, structure proteins, transcription regulatory factors and some elements correlated with horizontal transfer. Here we compare the complete genomic sequences of the two closely related species, which differ in pathogenic phenotype. To our knowledge, this not only reveals the difference of genomic sequence between the two important enteric pathogens for the first time, but also provides valuable clues to further researches in its process of physiological activity, pathogenesis and the evolution of enteric bacteria.展开更多
Nodulation is the predominant cellular defense reaction to bacterial challenges in insects. In this study, third instar larvae of Chrysomya megacephala were injected with bacteria, Escherichia coli K 12 （10^6 CFU/mL...Nodulation is the predominant cellular defense reaction to bacterial challenges in insects. In this study, third instar larvae of Chrysomya megacephala were injected with bacteria, Escherichia coli K 12 （10^6 CFU/mL, 2μL）, immediately prior to injection of inhibitors of eicosanoid biosynthesis, which sharply reduced nodulation response. Test larvae were treated with specific inhibitors ofphospholipase A2 （dexamethasone）, cyclo- oxygenase （indomethacin, ibuprofen and piroxicam）, dual cyclo-oxygenase/lipoxygenase （phenidone） and lipoxygenase （esculetin） and these reduced nodulation except esculetin. The influence of bacteria was obvious within 2 h of injection （5 nodules/larva）, and increased to a maximum after 8 h （with 15 nodules/larva）, and then significantly reduced over 24 h （9 nodules/larva）. The inhibitory influence of dexamethasone was apparent within 2 h of injection （4 vs. 5 nodules/larva）, and nodulation was significantly reduced, compared to control, over 24 h （5 vs. 8 nodules/larva）. Increased dosages of ibuprofen, indomethacin, piroxicam and phenidone led to decreased numbers of nodules. Nodules continued to exist during the pupal stage. However, the effects of dexamethasone were reversed by treating bacteria-injected insects with an eicosanoid-precursor polyunsaturated fatty acid, arachidonic acid. These findings approved our view that eicosanoid can mediate cellular defense mechanisms in response to bacterial infections in another Dipteran insect C. rnegacephala.展开更多
文摘The effect of antibacterial peptide CM4 of Bombyx mori against E. coll K12 was investigated using scanning electron microscopy(SEM) and transmission electron microscopy (TEM). The ultrastructural changes of E. coli K12 were observed by the challenge of the purified antibacterial peptide CM4. The results showed that the antibacterial peptide caused a series of pathological changes on E. coli. SEM and TEM revealed aggregates of bacteria and SEM revealed wrin-kled bacterial surfaces in the early stage. Thereafter, plasmolysis was observed with irregular holes appearing in the two ends of bacteria and the cytoplasmic contents of the cells leaking out. Finally, bacteria became empty vesicles and disintegrated into small fragments subsequently. Comparatively, the bacterial membrane was normal and the bacterial structure remained intact in the control group.
基金supported by the State“973”Key Basic Research Program(Grant No.G1999054103)the State“863”High-Tech Project(Grant No.Z19-02-05-01)+1 种基金Beijing Innovation Engineering(Grant No.955020700)the North China Pharmaceutical Corporation(NCPC)
文摘Comparative genome analysis is performed between Shigella flexneri 2a strain 301 and its close relatives, the nonpathogenic E. Coli K-12 strain MG1655. Result shows that there are 136 DNA segments whose size is larger than 1000 bp absent from Shigella flexneri 2a strain 301, which is up to 717253 bp in total length. These deleted segments altogether contain 670 open reading frames (ORFs). Prediction of these ORFs indicates that there are 40% genes of unknown function. The other genes of definite functions encode metabolic enzymes, structure proteins, transcription regulatory factors and some elements correlated with horizontal transfer. Here we compare the complete genomic sequences of the two closely related species, which differ in pathogenic phenotype. To our knowledge, this not only reveals the difference of genomic sequence between the two important enteric pathogens for the first time, but also provides valuable clues to further researches in its process of physiological activity, pathogenesis and the evolution of enteric bacteria.
文摘Nodulation is the predominant cellular defense reaction to bacterial challenges in insects. In this study, third instar larvae of Chrysomya megacephala were injected with bacteria, Escherichia coli K 12 （10^6 CFU/mL, 2μL）, immediately prior to injection of inhibitors of eicosanoid biosynthesis, which sharply reduced nodulation response. Test larvae were treated with specific inhibitors ofphospholipase A2 （dexamethasone）, cyclo- oxygenase （indomethacin, ibuprofen and piroxicam）, dual cyclo-oxygenase/lipoxygenase （phenidone） and lipoxygenase （esculetin） and these reduced nodulation except esculetin. The influence of bacteria was obvious within 2 h of injection （5 nodules/larva）, and increased to a maximum after 8 h （with 15 nodules/larva）, and then significantly reduced over 24 h （9 nodules/larva）. The inhibitory influence of dexamethasone was apparent within 2 h of injection （4 vs. 5 nodules/larva）, and nodulation was significantly reduced, compared to control, over 24 h （5 vs. 8 nodules/larva）. Increased dosages of ibuprofen, indomethacin, piroxicam and phenidone led to decreased numbers of nodules. Nodules continued to exist during the pupal stage. However, the effects of dexamethasone were reversed by treating bacteria-injected insects with an eicosanoid-precursor polyunsaturated fatty acid, arachidonic acid. These findings approved our view that eicosanoid can mediate cellular defense mechanisms in response to bacterial infections in another Dipteran insect C. rnegacephala.
