BACKGROUND Type Three Secretion Systems (T3SS) are nanomachine complexes, which display the ability to inject effector proteins directly into host cells. This skill allows for gram-negative bacteria to modulate several host cell responses, such as cytoskeleton rearrangement, signal transduction, and cytokine production, which in turn increase the pathogenicity of these bacteria. The Salmonella enterica subsp. enterica serovar Typhimurium (ST) T3SS has been the most characterized so far. Among gram-negative bacterium, ST is one of enterica groups predicted to have two T3SSs activated during different phases of infection. OBJECTIVE To comprise current information about ST T3SS structure and function as well as an overview of its assembly and hierarchical regulation. METHODS With a brief and straightforward reading, this review summarized aspects of both ST T3SS, such as its structure and function. That was possible due to the development of novel techniques, such as X-ray crystallography, cryoelectron microscopy, and nano-gold labelling, which also elucidated the mechanisms behind T3SS assembly and regulation, which was addressed in this review. CONCLUSION This paper provided fundamental overview of ST T3SS assembly and regulation, besides summarized the structure and function of this complex. Due to T3SS relevance in ST pathogenicity, this complex could become a potential target in therapeutic studies as this nanomachine modulates the infection process.

中文翻译：

---

鼠伤寒沙门氏菌的三型分泌系统：感染的关键。

背景技术类型三分泌系统（T3SS）是纳米机器复合物，其显示出将效应子蛋白直接注入宿主细胞的能力。该技能使革兰氏阴性细菌能够调节几种宿主细胞反应，例如细胞骨架重排，信号转导和细胞因子生成，从而增加这些细菌的致病性。沙门氏菌肠亚种。迄今为止，肠炎血清鼠伤寒（ST）T3SS的特征最为明显。在革兰氏阴性细菌中，ST是肠菌群之一，预计在感染的不同阶段会激活两个T3SS。目的包括有关ST T3SS结构和功能的最新信息，以及其组装和等级规定的概述。方法通过简要而直接的阅读，这篇综述总结了ST T3SS的各个方面，例如其结构和功能。由于新技术的发展（例如X射线晶体学，低温电子显微镜和纳米金标记），这是可能的，该技术也阐明了T3SS组装和调控的机制，本文对此进行了探讨。结论除了概述了该复合物的结构和功能外，本文还对ST T3SS的组装和调控进行了基本概述。由于T3SS与ST致病性相关，因此这种复合物可能成为治疗研究的潜在靶标，因为这种纳米机器可调节感染过程。本文还阐明了T3SS组装和监管背后的机制。结论除了概述了该复合物的结构和功能外，本文还对ST T3SS的组装和调控进行了基本概述。由于T3SS与ST致病性相关，因此这种复合物可能成为治疗研究的潜在靶标，因为这种纳米机器可调节感染过程。本文还阐明了T3SS组装和监管背后的机制。结论除了概述了该复合物的结构和功能外，本文还对ST T3SS的组装和调控进行了基本概述。由于T3SS与ST致病性相关，因此这种复合物可能成为治疗研究的潜在靶标，因为这种纳米机器可调节感染过程。