Nationat lnstitute ( ゾ Agro −Eni/ironmental Sciences ,3 −1・ 1 Kan ・ nondai , Tszaleuba , 305 / aPan StreP わ M3 」 'es are gram − positive soil bacteria that undergo a complex cycle of mor − phological differentiati 〔 } n , Thelr genome consists of single circular chromosomes whose size is approximately 104 kb . As they produce various kinds of antibiotics , they have attracted the attentions of researchers for many years. Recently, recombinant DNA techniques in Streptomyces have been developed

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... d gene cloning has made it posslble to carry out the experiments with Strep to myces which were impossible before. In the first part of this article , detailed accounts on the cloning experiments are given . The factors which should be considered in selecting host strains and vectors are listed . Genome fluidity of streptomycetes has been studied extel ユ sively . Most of the Stre . μ o 履 γ'彡splasmids possess a transfer function, which contributes to the exchange of genetic inforlnation between strains . Some important phenotypic traits can be lost due to extensive deletions inciuding structural genes for phenotypic traits stlldied along wlth considerable amplification of genorne segments , In studying the mechanism of integration of the plasmid SCPI into the S . coelicolor chromosome , a sequence of about 2kb was found to be present both on the 5. coelicoior chromosome and on SCP1 . This DNA segment was found to be