Molecular analyses and identifications of new genes to infectious diseases relating with oral biofilm

生物膜的形成与细菌的致病性有关，并且在细菌感染性疾病如龋齿中逃避免疫效应。许多研究者在体外实验中间接研究了口腔生物被膜的形成机制，这与口腔实际情况并不相似。在本研究中，我们试图确定在类似口腔条件下变形链球菌生物膜形成的易感基因。并进一步分析了该基因的表达与宿主基因（e2 f-1）的关系。首次研究了变形链球菌临床菌株在流动细胞系统中生物膜形成强度与基因表达的比较。通过脉冲场凝胶电泳，在从3岁儿童及其母亲的生物膜样品中分离的变形链球菌生物体中鉴定出17种不同的基因组DNA模式。变形链球菌分离株在流动池系统上形成生物膜的能力不同，当用共聚焦激光扫描显微镜（CLSM）检查时，FSC-3和FSC-4菌株分别显示出最大和最小的生物膜形成水平。此外，在FSC-3和FSC-4生物膜的比较中，DNA微阵列结果显示74个基因的差异表达超过4倍。在74个群体感应（quorum sensing，QS）系统基因中，鉴定出60%以上的CSP诱导基因，包括杆菌肽转运ATP结合蛋白bcrA和PTS系统IIA、B、C和D。对bcrA缺陷型菌株的分析显示，与野生型菌株相比，E2 F-1^<-/->小鼠牙齿表面上的生物膜形成和附着显著减少。结果表明，这些基因可能与宿主体内的E2 F-1基因相互作用，参与生物膜的形成。

A biofilm forming is associated with bacterial pathogenicity and escape from immunological effects in bacterial infectious diseases such as dental caries. Many investigators studied indirectly mechanism of oral biofilm in vitro assay, which is not similar to oral condition. In the present study, we attempted to identify susceptible genes for biofilm formation of Streptococcus mutans in similar condition to oral cavity. Further, we analyzed relationship between the gene expression and host gene (e2f-1) that response to byposalivation in mouse. Comparison of the intensity of biofilm formation by S.mutans clinical strains in flow cell system with the gene expression was firstly investigated. Seventeen different patterns of genomic DNA were identified in S.mutans organisms isolated from biofilm samples taken from 3-year-old children and their mothers by pulsed-field gel electrophoresis. The S.mutans isolates showed differing abilities to form biofilms on flow cell system and the FSC-3 and FSC-4 strains showed the greatest and least, respectively, levels of biofilm formation when examined with confocal laser scanning microscopy (CLSM). Further, in a comparison of FSC-3 and -4 biofilms, DNA microarray results showed 74 genes were differentially expressed more than 4-fold. We identified more than 60% CSP-induced genes of 74 in quorum sensing (QS) system, including bacitracin transport ATP-binding protein bcrA and PTS system IIA, B, C and D. Analyses of the bcrA deficient strains showed significant deceasing of biofilm formation and attachment on the tooth surface in E2F-1^<-/-> mouse in comparison with wild strain. Our results showed that these genes may play biofilm formation and interact with E2F-1 gene in host.