Bitespiramycin (biotechnological spiramycin, Bsm) is a new 16-membered macrolide antibiotic produced by Streptomyces spiramyceticus WSJ-1 integrated exogenous genes. The gene cluster for Bsm biosynthesis consists of two parts: spiramycin biosynthetic gene cluster (92 kb) and two exogenous genes including 4"-O-isovaleryltransferase gene (ist) and a positive regulatory gene (acyB2) from S. thermotolerans. Four putative regulatory genes, bsm2, bsm23, bsm27 and bsm42, were identified by sequence analysis in the spiramycin gene cluster. The inactivation of bsm23 or bsm42 in S. spiramyceticus eliminated spiramycin production, while the deletion of bsm2 and bsm27 did not abolish spiramycin biosynthesis. The acyB2 gene, homologous with bsm42 gene, cannot recover the spiramycin production in Δbsm42 mutant. The high expression of bsm42 significantly increased the spiramycin production, but overexpression of bsm23 inhibited its production in Δbsm23 and wild-type strain. Bsm23 was shown to be involved in the regulation of the expression of bsm42 and acyB2 by electrophoretic mobility shift assays. The bsm42 gene was also positive regulator for ist expression inferred from the improved yield of 4"-isovalerylspiramycins in the S. lividans TK24 biotransformation test, but adding bsm23 decreased the production of 4ʹʹ-isovalerylspiramycins. These results demonstrated Bsm42 was a pathway-specific activator for spiramycin or Bsm biosynthesis, but overexpression of Bsm23 alone was adverse to produce these antibiotics although Bsm23 was essential for positive regulation of spiramycin production.

必特螺旋霉素（b iotechnological小号PIRA米霉素，BSM）是一种新的16-元大环内酯抗生素所产生链霉菌spiramyceticus WSJ-1整合的外源基因。对于生物合成的Bsm基因簇由两个部分组成：螺旋霉素生物合成基因簇（92 KB）和两个外源基因，包括4" -O-isovaleryltransferase基因（IST）和正调节基因（acyB2从）S. thermotolerans四个假定的调节在spiramycin基因簇中通过序列分析鉴定了bsm2，bsm23，bsm27和bsm42基因。bsm23或bsm42在S. spiramyceticus消除螺旋霉素生产，同时删除BSM2和bsm27没有废除螺旋霉素生物合成。与bsm42基因同源的acyB2基因无法恢复Δbsm42突变体中的螺旋霉素生产。bsm42的高表达显着增加了螺旋霉素的生产，但bsm23的过表达抑制了它在Δbsm23和野生型菌株中的生产。已显示Bsm23参与bsm42和acyB2表达的调节通过电泳迁移率变化分析。所述bsm42基因也为正调节IST从4" -isovalerylspiramycins在改进的产率推断表达变青链霉菌TK24的生物转化试验，但加入bsm23生产4''-isovalerylspiramycins降低。这些结果证明Bsm42是一个特定途径活化剂对于螺旋霉素或Bsm生物合成而言，尽管Bsm23对于积极调节螺旋霉素的产生是必不可少的，但是仅Bsm23的过表达不利于产生这些抗生素。