Centre for Oral Health Science, Melbourne Dental School, The University of Melbourne, 720 Swanston Street, Victoria 3010, Australia.
J Bacteriol. 2010 Mar;192(5):1332-43. doi: 10.1128/JB.01211-09. Epub 2010 Jan 8.
Porphyromonas gingivalis is a late-colonizing bacterium of the subgingival dental plaque biofilm associated with periodontitis. Two P. gingivalis genes, fimR and fimS, are predicted to encode a two-component signal transduction system comprising a response regulator (FimR) and a sensor histidine kinase (FimS). In this study, we show that fimS and fimR, although contiguous on the genome, are not part of an operon. We inactivated fimR and fimS in both the afimbriated strain W50 and the fimbriated strain ATCC 33277 and demonstrated that both mutants formed significantly less biofilm than their respective wild-type strains. Quantitative reverse transcription-real-time PCR showed that expression of fimbriation genes was reduced in both the fimS and fimR mutants of strain ATCC 33277. The mutations had no effect, in either strain, on the P. gingivalis growth rate or on the response to hydrogen peroxide or growth at pH 9, at 41 degrees C, or at low hemin availability. Transcriptome analysis using DNA microarrays revealed that inactivation of fimS resulted in the differential expression of 10% of the P. gingivalis genome (>1.5-fold; P < 0.05). Notably genes encoding seven different transcriptional regulators, including the fimR gene and three extracytoplasmic sigma factor genes, were differentially expressed in the fimS mutant.
牙龈卟啉单胞菌是一种定植于牙周炎相关龈下菌斑生物膜的迟发细菌。牙龈卟啉单胞菌的两个基因 fimR 和 fimS 预测编码一个由应答调节子（FimR）和传感器组氨酸激酶（FimS）组成的双组分信号转导系统。在本研究中，我们表明 fimS 和 fimR 虽然在基因组上是连续的，但不是一个操纵子的一部分。我们在无纤毛菌株 W50 和纤毛菌株 ATCC 33277 中失活了 fimR 和 fimS，并证明这两个突变体形成的生物膜明显少于其相应的野生型菌株。定量逆转录实时 PCR 显示，纤毛形成基因的表达在 ATCC 33277 的 fimS 和 fimR 突变体中均降低。这两种突变在两种菌株中都没有影响牙龈卟啉单胞菌的生长速度，也没有影响其对过氧化氢的反应，或在 pH9、41°C 或低血红素供应条件下的生长。使用 DNA 微阵列进行的转录组分析表明，fimS 的失活导致 10%的牙龈卟啉单胞菌基因组的差异表达（>1.5 倍；P < 0.05）。值得注意的是，编码七个不同转录调节子的基因，包括 fimR 基因和三个细胞外 sigma 因子基因，在 fimS 突变体中差异表达。
