Yuan Lihui, Hillman Jeffrey D, Progulske-Fox Ann
Department of Oral Biology and Center for Molecular Microbiology, College of Dentistry, University of Florida, P.O. Box 100424, Gainesville, Florida 32610-0424, USA.
Infect Immun. 2005 Jul;73(7):4146-54. doi: 10.1128/IAI.73.7.4146-4154.2005.
Quorum sensing is a phenomenon defined as gene regulation in response to cell density that regulates various functions in bacteria. The periodontopathogen Porphyromonas gingivalis possesses a luxS gene homologue that may encode a quorum-sensing system. In order to identify genes of P. gingivalis that are regulated by luxS, gene expression analysis was done using microarrays and RNA samples from the W83 wild-type strain and an isogenic luxS mutant, LY2001. The results indicated that 17 open reading frames (ORFs) in LY2001 are upregulated and two are downregulated. Real-time PCR was done to confirm the microarray results. Among the upregulated ORFs is a group of stress-related genes, including htrA, clpB, groEL, dnaK, and the F subunit of alkyl hydroperoxide reductase. This suggested that luxS is involved in stress gene regulation in P. gingivalis. Stress response experiments, including high-temperature survival, resistance to hydrogen peroxide (H2O2), and survival during exposure to low and high pH, were performed on the P. gingivalis wild-type and LY2001 strains. LY2001 had a significantly higher survival rate than did W83 when stressed at 50 degrees C. No difference was found at pH 5, but LY2001 had increased survival compared to W83 at pH 9. LY2001 also survived better than W83 when stressed with 0.35 mM H2O2. These results suggest that luxS might be involved in promoting survival of P. gingivalis in the host by regulating its response to host-induced stresses such as temperature, H2O2, and pH.
群体感应是一种被定义为细菌中响应细胞密度而进行基因调控的现象，它调控着细菌的各种功能。牙周病原体牙龈卟啉单胞菌拥有一个luxS基因同源物，该同源物可能编码一种群体感应系统。为了鉴定受luxS调控的牙龈卟啉单胞菌基因，使用微阵列以及来自W83野生型菌株和同基因luxS突变体LY2001的RNA样本进行了基因表达分析。结果表明，LY2001中有17个开放阅读框（ORF）上调，2个下调。进行了实时PCR以确认微阵列结果。上调的ORF中有一组与应激相关的基因，包括htrA、clpB、groEL、dnaK以及烷基过氧化氢还原酶的F亚基。这表明luxS参与了牙龈卟啉单胞菌的应激基因调控。对牙龈卟啉单胞菌野生型和LY2001菌株进行了应激反应实验，包括高温存活、对过氧化氢（H2O2） 的抗性以及在低pH和高pH暴露期间的存活情况。在50摄氏度应激时，LY2001的存活率显著高于W83。在pH 5时未发现差异，但在pH 9时，LY2001的存活率相对于W83有所提高。在用0.35 mM H2O2应激时，LY2001的存活情况也优于W83。这些结果表明，luxS可能通过调节牙龈卟啉单胞菌对宿主诱导的应激（如温度、H2O2和pH）的反应，参与促进其在宿主体内的存活。
