非结核分枝杆菌(NTM)是包含超过200个个体物种的一大组微生物。大多数NTM是腐生生物,主要存在于陆地和水生环境中。近年来,NTM在免疫活性和免疫功能低下的个体中与感染越来越相关。促使人们做出重大努力来了解这些新兴病原体的多种致病和信号特征。自从发现VII型分泌系统(T7SS)以来,关于这些复杂系统在分枝杆菌中的作用已经取得了重大进展。这些专业系统,也称为早期抗原分泌(ESX)系统,用于通过内膜分泌蛋白质。它们在毒力方面也起着至关重要的作用,营养吸收和共轭。在过去的几年里,我们对分枝杆菌中T7SS的理解显著受益,从耻垢分枝杆菌ESX-3结构的分辨率来看,异种分枝杆菌和结核分枝杆菌的ESX-5结构。此外,ESX-4,直到最近才被认为是致病性和非致病性分枝杆菌的非功能性系统,已被认为在脓肿分枝杆菌的毒力中起重要作用;日益公认的机会性NTM引起严重的肺部疾病。这些重大发现导致了对这些生物系统的功能机制的重要新见解,它们在毒力中的含义,营养获取和细胞壁塑造,并将在本次审查中讨论。
Non-tuberculous mycobacteria (NTM) are a large group of micro-organisms comprising more than 200 individual species. Most NTM are saprophytic organisms and are found mainly in terrestrial and aquatic environments. In recent years, NTM have been increasingly associated with infections in both immunocompetent and immunocompromised individuals, prompting significant efforts to understand the diverse pathogenic and signalling traits of these emerging pathogens. Since the discovery of Type VII secretion systems (T7SS), there have been significant developments regarding the role of these complex systems in mycobacteria. These specialised systems, also known as Early Antigenic Secretion (
ESX) systems, are employed to secrete proteins across the inner membrane. They also play an essential role in virulence, nutrient uptake and conjugation. Our understanding of T7SS in mycobacteria has significantly benefited over the last few years, from the resolution of
ESX-3 structure in Mycobacterium smegmatis, to
ESX-5 structures in Mycobacterium xenopi and Mycobacterium tuberculosis. In addition,
ESX-4, considered until recently as a non-functional system in both pathogenic and non-pathogenic mycobacteria, has been proposed to play an important role in the virulence of Mycobacterium abscessus; an increasingly recognized opportunistic NTM causing severe lung diseases. These major findings have led to important new insights into the functional mechanisms of these biological systems, their implication in virulence, nutrient acquisitions and cell wall shaping, and will be discussed in this review.