Roles of the chemotaxis and the motility by flagella on environmental response of Vibio cells

霍乱弧菌有3组通用趋化信号蛋白(Che蛋白)和45种趋化感受器样蛋白(简称MLP)。系统I和III在染色体上分别有4个MLP基因和2个MLP基因，我们推测这些基因是Cheal和CheA3偶联的。系统II簇不含MLP基因。为了估计连接到三个ChE系统中任何一个的MLP基因，分析了初级序列，19个MLP与副溶血性弧菌的MLP相似，其中只有一个CheA与霍乱弧菌的CheA2同源。这19个MLP是与CheA2结合的候选者。为了验证这一假设，我们检查了甲基转移酶Cher的同源产物对MLP的甲基化作用。在M1p01和M1p45的C末端发现了与E.coliMCP的Cher结合序列相似的基序，在三个Cher同源物中，CheR3与E.coliCher的相似性最高。这个基序可能给出了cHER2的结合部位，对于MLP与推测的CheA2的甲基化是重要的。接下来，我们利用其GFP融合构建物研究了CHE系统组件的本地化。我们检测到系统II的ChE蛋白和MLP定位于鞭毛杆，系统I的一些成分也定位于鞭毛杆。在这些观测过程中，我们注意到系统I组分在一定条件下发生了扩散。当细胞生长到对数末期，剧烈摇动时，Cheal和CheY2没有定位，但在不摇动的情况下继续培养会导致它们的极地定位。此外，当空气被氮气取代时，抖动允许它们的极地局部化。呼吸作用的抑制剂也诱导了它们的极地定位。这些结果表明，一定的能量代谢状态诱导了Cheal和CheY2的极性局部化，增加了系统I在微厌氧条件下工作的可能性。

Vibrio cholerae has 3 sets of general chemotactic signaling proteins (Che proteins) and 45 chemoreceptor-like proteins (referred to as MLPs). Systems I cluster and III cluster in the chromosome have 4 mlp genes and 2 mlp genes, respectively, and we speculated that those genes were coupled CheAl and CheA3. System II cluster does not have mlp genes. To estimate the mlp genes coupled to any of the three Che systems, the primary sequences were analyzed and 19 MLPs have a similarity to MLPs of V. parahemolyticas which have only one CheA homologous to CheA2 of V. *cholerae. The 19 MLPs are candidates to couple with CheA2. To evaluate the assumption, the methylation of MLP by the homologous product of the methyl transfer enzyme CheR was examined. The similar motif as the CheR binding sequence of E. coli MCP was found in the C terminal region of M1p01 and M1p45, and CheR3 has the highest similarity to E. coli CheR among the three of the CheR homologs. This motif might give a binding site of CheR2 and is important for metylation of MLP coupled to the putative CheA2. Next, we examined the localization of Che system components by using their GFP fusion constructs. We detected that the Che proteins and MLPs of system II localize to the flagellated pole and some of the components of systems I were also shown to localize to the flagellated pole. During these observations, we noticed that the system I components were diffused under some conditions. When cells were grown to late logarithmic phase with vigorous shaking, CheAl and CheY2 did not localize but further incubation without shaking induced their polar localization. Moreover, when the air was replaced with nitrogen gas, shaking allowed their polar localization. Inhibitors of respiration also induced their polar localization. These results indicate that certain state of energy metabolism induces polar localization of CheAl and CheY2, raising the possibility that system I may work under microanaerobic conditions.