Investigating the molecular mechanisms of prey recognition and prey killing in the soil bacterium Myxococcus xanthus

研究土壤细菌黄粘球菌识别猎物和杀死猎物的分子机制

• 批准号: 412048565
• 负责人: Dr. Christine Kaimer
• 金额: --
• 依托单位: Lehrstuhl für Biologie der Mikroorganismen
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/412048565?language=en
• 关键词: Investigating; molecular; mechanisms; prey; recognition

The predatory soil bacterium Myxococcus xanthus kills other microorganisms to feed on their biomass. The multilayered predation strategy involves secretion of bactericidal antibiotics as well as bacteriolytic proteins, which accumulate within multicellular groups of M. xanthus and may enhance their predation efficiency. However, also single cells of M. xanthus are able to kill prey bacteria one-on-one in a contact-dependent manner. Here, a M. xanthus cell halts its motility when in contact with a prey cell and induces cell death and lysis within several minutes. Recently, we identified, by means of M. xanthus mutant analysis in different co-culture assays, two protein secretion systems that act together during cell contact-dependent killing of prey bacteria: a Tad-like system is required to induce prey cell death, while an atypical, needle-less type-3-secretion system (T3SS*) initiates prey cell disintegration. Mutation of both systems significantly reduces M. xanthus' ability to utilize biomass from bacteria and minimizes swarm expansion when growing on prey. Moreover, real time fluorescence microscopy revealed that components of both systems transiently accumulate at the predator-prey interface, presumably to deliver toxic effectors into the prey cell. To gain further insight into the functional interplay of the Tad-like and T3SS* systems during cell contact-dependent prey killing, the proposed research first addresses the translocation mechanism by the unusal, needle-less T3SS*. We aim to identify substrate proteins, to examine their translocation into the prey cell, and to determine the role of Tad components during this process. For this, we will take advantage on chaperone proteins, which likely recruit translocation substrates by direct protein-protein interaction (own preliminary data). Another focus of the project is the unknown mechanism of prey cell recognition. Our observation that the Tad/T3SS* killing machinery only accumulates upon contact with a prey cell, but not with another M. xanthus cell, provides a new read-out to investigate how M. xanthus indentifies a neighboring cell as prey. Here, we will systematically analyze Tad/T3SS* accumulation in M. xanthus paired with bacteria of different cell surface characteristics and of increasing phylogenetic distance. Furthermore, we will consider the putative role of known M. xanthus surface receptors, and compare predation to social incompatibility, which is mediated by the M. xanthus type-6-secretion system.

捕食性土壤细菌黄色粘球菌杀死其他微生物，以它们的生物量为食。多层捕食策略涉及分泌杀菌抗生素以及溶菌蛋白，其在M的多细胞群内积累。xanthus，并可能提高其捕食效率。然而，M. xanthus能够以接触依赖的方式一对一地杀死被捕食细菌。这里，一个M当与猎物细胞接触时，黄属细胞停止其运动，并在几分钟内诱导细胞死亡和溶解。最近，我们通过M.在不同的共培养分析中，两种蛋白质分泌系统在猎物细菌的细胞接触依赖性杀伤期间一起起作用：需要Tad样系统来诱导猎物细胞死亡，而非典型的无针3型分泌系统（T3 SS *）启动猎物细胞解体。两个系统的突变都显著降低了M。当在猎物上生长时，利用细菌的生物量和最小化群体扩张的能力。此外，真实的时间荧光显微镜显示，这两个系统的组成部分瞬时积累在捕食者-猎物界面，大概提供到猎物细胞的毒性效应。为了进一步了解Tad样和T3 SS * 系统在细胞接触依赖性猎物杀伤过程中的功能相互作用，该研究首先通过不寻常的无针T3 SS * 解决了易位机制。我们的目标是确定底物蛋白，检查他们的易位到猎物细胞，并确定在这个过程中的作用Tad组件。为此，我们将利用分子伴侣蛋白，其可能通过直接蛋白质-蛋白质相互作用招募易位底物（自己的初步数据）。 该项目的另一个重点是未知的猎物细胞识别机制。我们观察到Tad/T3 SS * 杀伤机制只在与猎物细胞接触时积累，而不是与另一个M。xanthus细胞，为研究M. xanthus将邻近的细胞识别为猎物。在这里，我们将系统地分析Tad/T3 SS * 在M中的积累。xanthus与不同细胞表面特征的细菌配对，并增加系统发育距离。此外，我们将考虑已知M的假定作用。xanthus表面受体，并将捕食与社会不相容性进行比较，这是由M. xanthus type-6-分泌系统。