Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA, USA.
J Bacteriol. 2012 Jun;194(11):2781-90. doi: 10.1128/JB.06780-11. Epub 2012 Feb 10.
Biofilms of microbial cells encased in an exopolymeric matrix can form on solid surfaces, but how bacteria sense a solid surface and upregulate biofilm genes is largely unknown. We investigated the role of the Bacillus subtilis signal peptidase, SipW, which has a unique role in forming biofilms on a solid surface and is not required at an air-liquid interface. Surprisingly, we found that the signal peptidase activity of SipW was not required for solid-surface biofilms. Furthermore, a SipW mutant protein was constructed that lacks the ability to form a solid-surface biofilm but still retains signal peptidase activity. Through genetic and gene expression tests, the non-signal peptidase role of SipW was found to activate biofilm matrix genes specifically when cells were on a solid surface. These data provide the first evidence that a signal peptidase is bifunctional and that SipW has a regulatory role in addition to its role as a signal peptidase.
微生物细胞被胞外聚合基质包裹形成的生物膜可以在固体表面形成，但细菌如何感知固体表面并上调生物膜基因在很大程度上仍是未知的。我们研究了枯草芽孢杆菌信号肽酶 SipW 的作用，它在固体表面形成生物膜方面具有独特的作用，而在气液界面则不需要。令人惊讶的是，我们发现 SipW 的信号肽酶活性对于固体表面生物膜的形成并不是必需的。此外，构建了一种 SipW 突变蛋白，它丧失了形成固体表面生物膜的能力，但仍保留信号肽酶活性。通过遗传和基因表达测试，发现 SipW 的非信号肽酶作用在细胞位于固体表面时，特异性地激活生物膜基质基因。这些数据首次提供了证据，证明信号肽酶具有双重功能，SipW 除了作为信号肽酶外，还具有调节作用。
