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Category: Microbial Genetics and Molecular Biology
Virulence Plasmids of Spore-Forming Bacteria, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817732/9781555812652_Chap19-1.gif /docserver/preview/fulltext/10.1128/9781555817732/9781555812652_Chap19-2.gifAbstract:
Spore-forming bacteria are the causative agents of some of the most dramatic life-threatening human and animal infections and toxemias, including diseases such as tetanus, botulism, gas gangrene, pseudomembranous colitis, and anthrax. This chapter reviews the current state of knowledge of virulence plasmids of the Clostridia and the bacilli. Although other pathogens are mentioned, the focus is on the major human pathogens, Clostridium perfringens and Bacillus anthracis, primarily because most is known about virulence plasmids in these species. The major toxins involved in C. perfringens type A-mediated gas gangrene, the α-toxin and perfringolysin O, together with other extracellular toxins such as collagenase and hyaluronidase, are chromosomally encoded. Along with tetanus, botulism, and gas gangrene, anthrax is one of the four classical diseases that are caused by spore-forming bacteria. Expression of the plasmid-determined toxin genes in Bacillus thuringiensis is coordinately regulated with the sporulation process and therefore clearly involves chromosomal regulatory genes. Toxin-producing strains often carry multiple cry genes and large amounts of the δ-endotoxins are produced in stationary phase, to the extent that the crystalline inclusion may account for more than 20% of the cell's dry weight.
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Regulation of anthrax toxin production and capsule biosynthesis in B. anthracis. Only relevant genes on pXO1 and pXO2 are shown. Neither the plasmids nor the genes are drawn to scale. The arrows indicate transcriptional activation, the bars indicate transcriptional repression.
Regulation of anthrax toxin production and capsule biosynthesis in B. anthracis. Only relevant genes on pXO1 and pXO2 are shown. Neither the plasmids nor the genes are drawn to scale. The arrows indicate transcriptional activation, the bars indicate transcriptional repression.
Genetic location of toxins and extracellular enzymes of C. perfringens
Genetic location of toxins and extracellular enzymes of C. perfringens