Center for Medical, Agricultural and Veterinary Entomology, USDA-ARS, Gainesville, FL, USA.
J Chem Ecol. 2009 Aug;35(8):878-92. doi: 10.1007/s10886-009-9670-0. Epub 2009 Aug 4.
Caenorhabditis elegans, a bacterivorous nematode, lives in complex rotting fruit, soil, and compost environments, and chemical interactions are required for mating, monitoring population density, recognition of food, avoidance of pathogenic microbes, and other essential ecological functions. Despite being one of the best-studied model organisms in biology, relatively little is known about the signals that C. elegans uses to interact chemically with its environment or as defense. C. elegans exudates were analyzed by using several analytical methods and found to contain 36 common metabolites that include organic acids, amino acids, and sugars, all in relatively high abundance. Furthermore, the concentrations of amino acids in the exudates were dependent on developmental stage. The C. elegans exudates were tested for bacterial chemotaxis using Pseudomonas putida (KT2440), a plant growth promoting rhizobacterium, Pseudomonas aeruginosa (PAO1), a soil bacterium pathogenic to C. elegans, and Escherichia coli (OP50), a non-motile bacterium tested as a control. The C. elegans exudates attracted the two Pseudomonas species, but had no detectable antibacterial activity against P. aeruginosa. To our surprise, the exudates of young adult and adult life stages of C. elegans exudates inhibited quorum sensing in the reporter system based on the LuxR bacterial quorum sensing (QS) system, which regulates bacterial virulence and other factors in Vibrio fischeri. We were able to fractionate the QS inhibition and bacterial chemotaxis activities, thus demonstrating that these activities are chemically distinct. Our results demonstrate that C. elegans can attract its bacterial food and has the potential of partially regulating the virulence of bacterial pathogens by inhibiting specific QS systems.
秀丽隐杆线虫，一种食细菌线虫，生活在复杂的腐烂水果、土壤和堆肥环境中，其交配、监测种群密度、识别食物、避免病原微生物等重要生态功能都需要化学相互作用。尽管它是生物学中研究得最好的模式生物之一，但人们对秀丽隐杆线虫用于与环境进行化学相互作用或作为防御的信号知之甚少。使用几种分析方法分析秀丽隐杆线虫的分泌物，发现其中含有 36 种常见代谢物，包括有机酸、氨基酸和糖，且含量都相对较高。此外，分泌物中氨基酸的浓度依赖于发育阶段。使用植物促生根际细菌假单胞菌（KT2440）、一种对秀丽隐杆线虫致病的土壤细菌铜绿假单胞菌（PAO1）和非运动细菌大肠杆菌（OP50）作为对照，测试秀丽隐杆线虫分泌物对细菌的趋化性。秀丽隐杆线虫分泌物吸引了两种假单胞菌，但对铜绿假单胞菌没有检测到抗菌活性。令我们惊讶的是，秀丽隐杆线虫幼体和成虫期的分泌物抑制了基于 LuxR 细菌群体感应（QS）系统的报告系统中的群体感应，该系统调节了发光杆菌中的细菌毒力和其他因素。我们能够对群体感应抑制和细菌趋化性活动进行分级，从而表明这些活动在化学上是不同的。我们的研究结果表明，秀丽隐杆线虫可以吸引其细菌食物，并通过抑制特定的 QS 系统，有可能部分调节细菌病原体的毒力。
