Roles of the alpha-,theta-,and k-toxins in histotoxicity of Clostridium perfringens

点击翻译按钮获取中文摘要

Genes encoding for alpha-and theta-toxins of Clostridium perfringens(type A NCTC 8237)were separately cloned into pHY300PLK and expressed in Bacillus subtilis ISW 1214(spoo^).Levels of both the alpha- and theta-toxins produced by each strain were almost the same as those by C.perfringens. Viability of these two strains within a macrophage was examined using macrophage cell line SV-BP-1.The theta-toxin producing strain increased in number within the macrophage,while the alpha-toxin producing strain decreased similarly to a control.The result indicates that the theta-toxin functions as an antiphagocytic determinant but the alpha-toxin does not.Virulence of the two strains was examined by determining lethal dose against a mouse. When the alpha-toxin producing strain was injected interperitoneally,it was more virulent than the theta-toxin producing strain. On the other hand,the former was less virulent than the latter when injected intravenously. A plasmid carrying the two toxin genes was also constructed.B subtilis carrying this plasmid produced the theta-toxin in large amounts but the alpha-toxin in a very small amount. However,the strain producing the two toxins exhibited mouse lethality to the same extent as the two alpha- and theta-producing strains used in combination, suggesting that a synergistic effect of the two toxins may be enhanced if they are produced by a single cell into microenvironment surrounding a bacterial cell.A 120-KDa C.perfringens collagenase(k-toxin)was found and purified. Its encoding gene was cloned and sequenced. The nucleotide sequence shows that the toxin belongs to Zn metalloproteinase and is homologous to other bacterial proteinase and collagenase.