Effects of cell-to-cell communication on Pseudomonas aeruginosa biofilm alginate biosynthesis

當微生物細胞吸附在含有水分的 固體表面時，微生物會繼續生長複 製，同時也會製造胞外的聚合物，這 種由細胞及其胞外聚合物所組成且具 有生物活性的薄膜就是所謂的生物 膜。生物膜的形成會增加質量、熱量 及動量輸送的阻力，影響整體系統的 效率;會與吸附的表面起生物或化學 反應，造成腐蝕的現象;也會感染醫療 器材，危害人體的健康。生物膜防治 係微生物在人為系統造成危害中最困 擾人們的一個問題，主要因為生物膜 胞外聚合物會影響輸送效率。胞外聚 合物的存在，使得使用抑制微生物生 長的化學物質效果不盡理想。一般而 言，大致要500 到1000 倍濃度的化學 殺菌劑或抗生素才能達到跟懸浮細胞 同樣的殺菌效果，而這種高劑量在實 際應用上卻不可行。胞外聚合物影響 生物膜輸送現象係指微生物抑制劑在 生物膜中被胞外聚合物中和或吸附較 其擴散為快，與生物膜細胞起作用的 微生物抑制劑遠低於原先的劑量。目 前已知細胞與細胞間的聯繫是靠 homoserine lactones (HSL)這一類的物 質。其中綠膿桿菌的野生株 ( Pseudomonas aeruginosa PAO1)已被 鑑定出兩種基因lasI及rhlI和HSL 的 合成有關。P. aeruginosa生物膜的胞外 聚合物主要成份之一是藻酸鹽，而藻 酸鹽的生成與algC基因的表現有關。 本計畫將探討algC基因的表現是否受 到細胞對細胞之聯繫的影響。As microbial cells attached to solid surfaces with moisture, microbial cells will grow, duplicate and produce extracellular polymers; the collective surface community with biological activity referred to as a biofilm. The formation of biofilms will lead to increase the transfer resistance of mass, heat and momentum, and thus reduce the efficiency of overall systems; biological and chemical reaction with attached surfaces and cause corrosion; and infection of medical devise and health risk. The decrease in transfer efficiency is the major reason to lead the biofilm problems. The existence of extracellular polymers has limited the effect of chemical biocides against biofilms. It typically requires 500 to 1000 times of higher concentrations to achieve the same degree of killing as in suspended cultures. Transport limitation is attributed to the neutralization of the antimicrobial agent in the biofilm faster than it can diffuse in. Scientists have known that cells can communicate with each other via homeseine lactones (HSL). Two genes ( lasI and rhlI) with the capability of biosynthesizing HSL have been identified from wild type of Pseudomonas aeruginosa PAO1. The primary extracellular polymers of P. aeruginosa are alginates whose biosynthesis is related to the expression of algC. This proposal will study the effects of cell-to-cell communication on the gene expression of algC