Nakano M M, Marahiel M A, Zuber P
Department of Botany and Microbiology, Oklahoma State University, Stillwater 74078.
J Bacteriol. 1988 Dec;170(12):5662-8. doi: 10.1128/jb.170.12.5662-5668.1988.
Surfactin is a lipopeptide antibiotic produced by the cells of Bacillus subtilis ATCC 21332. A genetic locus responsible for surfactin production (sfp) was transferred from ATCC 21332 to JH642, a derivative of the standard B. subtilis 168. To study the sfp locus at the molecular level, a Tn917 insertion mutant that was blocked in surfactin production (srf) was isolated. The srf::Tn917 mutation was found to be closely linked to sfp, and both loci mapped by PBS1 phage transduction to the chromosomal region between aroI and mtlB. These studies suggest that JH642, a strain which is not a producer of surfactin (genotypically sfp0), contains at least some of the genes encoding surfactin production. Expression of the srf gene(s) was examined in both sfp and sfp0 cells by assaying beta-galactosidase activity encoded by a promoterless lacZ gene that was fused to the srf::Tn917 insertion. In cells of both strains, srf-directed beta-galactosidase activity increased when cells entered the stationary phase of the growth curve, but the activity in sfp cells was higher than that in sfp0 cells. srf-lacZ expression was partially impaired by a mutation in spo0A. In sfp0 cells, this dependence on the spo0A gene product could be entirely bypassed by an abrB suppressor mutation. In the sfp cells, the abrB mutation could not restore the defect conferred by the spo0A mutation. These data suggest that the sfp locus, which is responsible for surfactin production, alters the transcriptional regulation of srf in JH642 cells.
表面活性素是由枯草芽孢杆菌ATCC 21332细胞产生的一种脂肽抗生素。负责表面活性素产生的基因座（sfp）从ATCC 21332转移到了JH642，JH642是标准枯草芽孢杆菌168的衍生物。为了在分子水平上研究sfp基因座，分离出了一个在表面活性素产生方面受阻的Tn917插入突变体（srf）。发现srf::Tn917突变与sfp紧密连锁，并且这两个基因座通过PBS1噬菌体转导定位到aroI和mtlB之间的染色体区域。这些研究表明，JH642这个不产生表面活性素的菌株（基因型为sfp0）至少包含一些编码表面活性素产生的基因。通过检测由与srf::Tn917插入融合的无启动子lacZ基因编码的β-半乳糖苷酶活性，在sfp和sfp0细胞中研究了srf基因的表达。在两种菌株的细胞中，当细胞进入生长曲线的稳定期时，srf导向的β-半乳糖苷酶活性增加，但sfp细胞中的活性高于sfp0细胞中的活性。spo0A突变会部分损害srf-lacZ的表达。在sfp0细胞中，这种对spo0A基因产物的依赖性可以被abrB抑制突变完全绕过。在sfp细胞中，abrB突变不能恢复spo0A突变导致的缺陷。这些数据表明，负责表面活性素产生的sfp基因座改变了JH642细胞中srf的转录调控。
