Crystal structure of a cholera toxin-related heat-labile enterotoxin from E. coli

Examination of the structure of Escherichia coli heat-labile enterotoxin in the AB5 complex at a resolution of 2.3A reveals that the doughnut-shaped B pentamer binds the enzymatic A subunit using a hairpin of the A2 fragment, through a highly charged central pore. Putative ganglioside GM1-binding sites on the B subunits are more than 20A removed from the membrane-crossing A1 subunit. This ADP-ribosylating (A1) fragment of the toxin has structural homology with the catalytic region of exotoxin A and hence also to diphtheria toxin.     

PCR技术检测金黄色葡萄球菌肠毒素D基因

根据金黄色葡萄球菌肠毒素Ｄ基因的序列,设计相应的引物,建立检测金黄色葡萄球菌肠毒素Ｄ基因的ＰＣＲ技术。利用该方法可从含有肠毒素Ｄ基因的金黄色葡萄球菌中扩增出ＰＣＲ产物。扩增产物具有特异性,长为３１６个碱基对。经限制性核酸内切酶ＨｈＩⅠ酶切证实扩增产物为ＳＥＤ基因片段。     

北疆棉花根际微生物对棉花立枯病拮抗作用的研究

从石河子地区棉花根际土壤中采集土样３６份,经室内分离,纯化后获得生长数量占优势的菌株各１０８个共计３２４个,对棉花立枯病的病原菌进行平板双培养法拮抗测定,共筛选出１００个有拮抗活性的菌株,对之进行筛选,比较后,选出拮抗活性较强的９个菌株进行盆栽试验,最后确定了７个拮抗菌株。     

Protein deprivation causes reversible impariment of mucosal immune response to cholera toxoid/toxin in rat gut

Scretory antibodies may be the major defence against mucosal infections, especially those due to viruses and non-invasive pathogens such as Vibrio cholerae and toxinogenic Escherichia coli. The high incidence of mucosal infections in malnourished protein-deficient children may result from defective antibody production, but evidence for this is conflicting. We report here that protein deficiency markedly impairs the mucosal immune reponse to cholera toxiod/toxin (CT), a protein antigen, in rats and that this impairment is rapidly reversed by refeeding.