NHC Key Laboratory of Biotechnology of Antibiotics, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China.
CAMS Key Laboratory of Synthetic Biology for Drug Innovation, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, China.
Microbiol Res. 2020 Nov;240:126532. doi: 10.1016/j.micres.2020.126532. Epub 2020 Jun 27.
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 4''-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.
比西霉素（生物技术螺旋霉素，Bsm）是由链霉菌螺旋体 WSJ-1 整合外源基因产生的一种新型 16 元大环内酯抗生素。Bsm 生物合成基因簇由两部分组成：螺旋霉素生物合成基因簇（92kb）和两个外源基因，包括来自嗜热链霉菌的 4"-O-异戊酰基转移酶基因（ist）和一个正调控基因（acyB2）。在螺旋霉素基因簇中，通过序列分析鉴定了四个假定的调控基因 bsm2、bsm23、bsm27 和 bsm42。在链霉菌中敲除 bsm23 或 bsm42 会消除螺旋霉素的产生，而敲除 bsm2 和 bsm27 并不会完全阻止螺旋霉素的生物合成。acyB2 基因与 bsm42 基因同源，不能恢复 bsm42 突变体中的螺旋霉素产量。bsm42 的高表达显著增加了螺旋霉素的产量，但 bsm23 的过表达抑制了 bsm23 和野生型菌株中的螺旋霉素产量。电泳迁移率变动分析表明，bsm23 参与了 bsm42 和 acyB2 表达的调控。bsm42 基因也是 ist 表达的正调控因子，这可以从 S. lividans TK24 生物转化试验中 4"-异戊酰基螺旋霉素产量的提高推断出来，但添加 bsm23 会降低 4''-异戊酰基螺旋霉素的产量。这些结果表明 Bsm42 是螺旋霉素或 Bsm 生物合成的途径特异性激活剂，但单独过表达 Bsm23 不利于产生这些抗生素，尽管 Bsm23 是螺旋霉素产量正调控所必需的。
