Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi, Japan.
Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan.
Genes Cells. 2022 Sep;27(9):568-578. doi: 10.1111/gtc.12975. Epub 2022 Aug 1.
Marine bacterium Vibrio alginolyticus forms a single flagellum at a cell pole. In Vibrio, two proteins (GTPase FlhF and ATPase FlhG) regulate the number of flagella. We previously isolated the NMB155 mutant that forms multiple flagella despite the absence of mutations in flhF and flhG. Whole-genome sequencing of NMB155 identified an E9K mutation in FliM that is a component of C-ring in the flagellar rotor. Mutations in FliM result in defects in flagellar formation (fla) and flagellar rotation (che or mot); however, there are a few reports indicating that FliM mutations increase the number of flagella. Here, we determined that the E9K mutation confers the multi-flagellar phenotype and also the che phenotype. The co-expression of wild-type FliM and FliM-E9K indicated that they were competitive in regard to determining the flagellar number. The ATPase activity of FlhG has been correlated with the number of flagella. We observed that the ATPase activity of FlhG was increased by the addition of FliM but not by the addition of FliM-E9K in vitro. This indicates that FliM interacts with FlhG to increase its ATPase activity, and the E9K mutation may inhibit this interaction. FliM may control the ATPase activity of FlhG to properly regulate the number of the polar flagellum at the cell pole.
海洋细菌弧菌 alginolyticus 在细胞的一个极形成一个鞭毛。在弧菌中，两种蛋白（GTPase FlhF 和 ATPase FlhG）调节鞭毛的数量。我们之前分离出了 NMB155 突变体，尽管在 flhF 和 flhG 中没有突变，但它形成了多个鞭毛。NMB155 的全基因组测序鉴定出 FliM 中的 E9K 突变，该突变是鞭毛转子 C 环的一个组成部分。FliM 的突变导致鞭毛形成（fla）和鞭毛旋转（che 或 mot）缺陷；然而，有一些报道表明 FliM 突变会增加鞭毛的数量。在这里，我们确定 E9K 突变赋予了多鞭毛表型，也赋予了 che 表型。野生型 FliM 和 FliM-E9K 的共表达表明它们在确定鞭毛数量方面具有竞争力。FlhG 的 ATPase 活性与鞭毛的数量有关。我们观察到 FlhG 的 ATPase 活性在体外通过添加 FliM 而不是添加 FliM-E9K 而增加。这表明 FliM 与 FlhG 相互作用以增加其 ATPase 活性，而 E9K 突变可能抑制这种相互作用。FliM 可能控制 FlhG 的 ATPase 活性，以正确调节细胞极的极性鞭毛的数量。
