Department of Medical Microbiology and Immunology, University of Wisconsin, Madison, USA.
Appl Environ Microbiol. 2012 Jul;78(13):4620-6. doi: 10.1128/AEM.00377-12. Epub 2012 Apr 20.
Chitin, a polymer of N-acetylglucosamine (GlcNAc), is noted as the second most abundant biopolymer in nature. Chitin serves many functions for marine bacteria in the family Vibrionaceae ("vibrios"), in some instances providing a physical attachment site, inducing natural genetic competence, and serving as an attractant for chemotaxis. The marine luminous bacterium Vibrio fischeri is the specific symbiont in the light-emitting organ of the Hawaiian bobtail squid, Euprymna scolopes. The bacterium provides the squid with luminescence that the animal uses in an antipredatory defense, while the squid supports the symbiont's nutritional requirements. V. fischeri cells are harvested from seawater during each host generation, and V. fischeri is the only species that can complete this process in nature. Furthermore, chitin is located in squid hemocytes and plays a nutritional role in the symbiosis. We demonstrate here that chitin oligosaccharides produced by the squid host serve as a chemotactic signal for colonizing bacteria. V. fischeri uses the gradient of host chitin to enter the squid light organ duct and colonize the animal. We provide evidence that chitin serves a novel function in an animal-bacterial mutualism, as an animal-produced bacterium-attracting synomone.
几丁质是 N-乙酰氨基葡萄糖（GlcNAc）的聚合物，是自然界中第二丰富的生物聚合物。几丁质为弧菌科（“弧菌”）的海洋细菌提供了多种功能，在某些情况下提供物理附着位点、诱导自然遗传能力，并作为趋化性的吸引剂。海洋发光细菌费氏弧菌是夏威夷短尾乌贼发光器官中的特定共生菌，Euprymna scolopes。细菌为鱿鱼提供发光，动物在反捕食防御中使用这种发光，而鱿鱼则支持共生体的营养需求。在每个宿主世代中，从海水中收获 V. fischeri 细胞，并且 V. fischeri 是自然界中唯一能够完成此过程的物种。此外，几丁质位于鱿鱼血细胞中，并在共生关系中发挥营养作用。我们在这里证明，鱿鱼宿主产生的几丁质低聚糖作为定植细菌的趋化信号。V. fischeri 利用宿主几丁质的梯度进入鱿鱼光器官导管并定植动物。我们提供的证据表明，几丁质在动物-细菌共生关系中发挥了新的功能，作为一种动物产生的细菌吸引共生激素。
