中文摘要：

普城沙雷氏菌（Serratia plymuthica）G3分离自小麦内茎，是一种可产生多种抗菌因子和植物激素的内生细菌。目前对S．plymuthicaG3的两个群体感应系统spll／splR与SpsR／SpsI的了解仍十分有限。构建了2个N-乙酰基高丝氨酸内酯信号合成酶编码基因splI和spsI突变菌株及互补菌株，并检测了其生物表型。结果发现spsI、splI突变后，对细菌信号分子合成有一定的影响，蛋白酶活性明显降低。通过对突变体和互补菌株的泳动性分析发现，splI负调控G3的运动性，而spsl正调控G3的运动性。

英文摘要：

An endophytie strain G3 of Serratia plymuthica isolated from the stems of wheat can be used as biocontrol agent against variety of phytopathogeuic fungi due to its ability to produce several antifungal factors, as well as plant auxin indole-3-acetic acid （IAA）. So far, our knowledge about the two Quorum sensing （QS） systems （SplI/SplR and SpsR/SpsI） in S. plymuthica G3 is still very limited. In this study, strain G3 was used as the model organism, splI and spsl mutants in G3 through gene-replacement strategy were con- structed. The phenotypic analysis of G3 and its derivatives revealed that mutation of spsI and splI slightly affected the biosysthesis of bacterial signal molecules N-acylhomoserine lactones （ AHLs）, However, these tow mutants significantly decreased the protease activity in comparision with the wild type G3. Furthermore, swimming assay of the mutants and the complementary strains showed that splI negatively regulated the swimming motility of G3, in contrast, spsl positively controlled the swimming motility of strain G3. These findings provided a basis for further studies of the two QS systems in Serratia.