Genetic designs for product formation in recombinant microbes.
Several new bacterial host-vector systems for Klebsiella, Erwinia, Xanthomonas, Nocardia, and Streptomyces have been developed. With these host-vector systems, a strain of Klebsiella, which overproduces the extracellular starch-debranching enzyme, pullulanase, has been developed. The gene for cholesterol oxidase was cloned and used to develop a strain of Streptomyces lividans that extracellularly produces the enzyme, cholesterol oxidase, which is utilized to process cholesterol and diagnostically. The genes for these two enzymes were sequenced, and several interesting facts about their structures and secretory mechanisms were found. For expression of mammalian gene products, the expression vectors. pYM001 to pYM008, containing the lambda P(R)P(L) promoter, which is controlled by a thermolabile repressor, have been developed. The activities of these promoters were compared in various bacterial strains with the galK monitoring system. E. coli promoters, such as lac, trp, tac, lambda P(R), P(L), and P(R)P(L), were found to be expressed in other enteric bacteria and in Bacillus subtilis. With these expression vectors, the vesicular stomatitis virus-nucleocapsid, monkey metallothionein, and human apolipoprotein A1 genes were expressed in E. coli.
Murooka
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Laboratory of Genetic Engineering, Department of Fermentation Technology, Faculty of Engineering, Hiroshima University, Saijo, Higashi-Hiroshima, Japan.