Saak Christina C, Gibbs Karine A
Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, USA.
Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, USA
J Bacteriol. 2016 Nov 18;198(24):3278-3286. doi: 10.1128/JB.00402-16. Print 2016 Dec 15.
Proteus mirabilis is a social bacterium that is capable of self (kin) versus nonself recognition. Swarming colonies of this bacterium expand outward on surfaces to centimeter-scale distances due to the collective motility of individual cells. Colonies of genetically distinct populations remain separate, while those of identical populations merge. Ids proteins are essential for this recognition behavior. Two of these proteins, IdsD and IdsE, encode identity information for each strain. These two proteins bind in vitro in an allele-restrictive manner. IdsD-IdsE binding is correlated with the merging of populations, whereas a lack of binding is correlated with the separation of populations. Key questions remained about the in vivo interactions of IdsD and IdsE, specifically, whether IdsD and IdsE bind within single cells or whether IdsD-IdsE interactions occur across neighboring cells and, if so, which of the two proteins is exchanged. Here we demonstrate that IdsD must originate from another cell to communicate identity and that this nonresident IdsD interacts with IdsE resident in the recipient cell. Furthermore, we show that unbound IdsD in recipient cells does not cause cell death and instead appears to contribute to a restriction in the expansion radius of the swarming colony. We conclude that P. mirabilis communicates IdsD between neighboring cells for nonlethal kin recognition, which suggests that the Ids proteins constitute a type of cell-cell communication.
We demonstrate that self (kin) versus nonself recognition in P. mirabilis entails the cell-cell communication of an identity-encoding protein that is exported from one cell and received by another. We further show that this intercellular exchange affects swarm colony expansion in a nonlethal manner, which adds social communication to the list of potential swarm-related regulatory factors.
奇异变形杆菌是一种具有自我（亲缘）与非自我识别能力的群居细菌。由于单个细胞的集体运动，这种细菌的群体在表面向外扩展至厘米级距离。基因不同群体的菌落保持分离，而相同群体的菌落则会融合。Ids蛋白对于这种识别行为至关重要。其中两种蛋白，IdsD和IdsE，编码每个菌株的身份信息。这两种蛋白在体外以等位基因限制性方式结合。IdsD-IdsE结合与群体融合相关，而缺乏结合则与群体分离相关。关于IdsD和IdsE在体内的相互作用仍存在关键问题，具体而言，IdsD和IdsE是在单个细胞内结合，还是在相邻细胞间发生相互作用，如果是后者，两种蛋白中哪一种会进行交换。在这里，我们证明IdsD必须源自另一个细胞才能传递身份信息，并且这种非驻留的IdsD与受体细胞中驻留的IdsE相互作用。此外，我们表明受体细胞中未结合的IdsD不会导致细胞死亡，反而似乎有助于限制群体菌落的扩展半径。我们得出结论，奇异变形杆菌在相邻细胞间传递IdsD以进行非致死性亲缘识别，这表明Ids蛋白构成了一种细胞间通讯方式。
我们证明奇异变形杆菌中的自我（亲缘）与非自我识别需要一种身份编码蛋白在细胞间进行通讯，该蛋白从一个细胞输出并被另一个细胞接收。我们进一步表明这种细胞间交换以非致死方式影响群体菌落扩展，这为潜在的与群体相关的调控因子列表增添了社会通讯这一因素。
