不动杆菌属病原菌由于其强大的适应性,在全球范围内对人类健康构成严重威胁,容忍度,抗生素耐药性。这些细菌的大多数分离物都具有VI型分泌系统(T6SS),使它们能够胜过共同居住的微生物,但是该系统是否参与从猎物中获取营养的研究还很少。在这项研究中,我们发现Ab25,一种临床分离的不动杆菌,利用T6SS杀死分类学上不同的微生物,包括细菌和真菌。Ab25的T6SS组成型表达,在三个预测的效应器中,T6e1,RHS效应子家族的成员,对其抗菌活性贡献最大。T6e1经历自我分裂,具有核酸酶活性的短羧基片段足以通过T6SS注射杀死靶细胞。有趣的是,Ab25菌株编码孤儿VgrG蛋白,当过度表达时,会阻止其T6SS的发射。在干燥的塑料表面等壁龛中,T6SS促进Ab25的猎物微生物依赖性存活。这些结果表明,A.noconomialis采用T6SS,其调节和效应物组成高度多样化,以在营养供应稀缺和竞争微生物的环境中获得竞争优势。重要性VI型分泌系统(T6SS)在细菌适应环境挑战中起着重要作用。不动杆菌属的成员,特别是鲍曼不动杆菌和医院内杆菌,因其多重耐药性和在恶劣环境中生存的能力而臭名昭著。与鲍曼不动杆菌相反,其T6SS已经得到了充分的研究,很少有研究工作集中在A。在这项研究中,我们发现,A.noconomialis菌株利用一种具有良好活性的T6SS来杀死多种微生物,包括细菌和真菌。尽管细胞内A.的T6SS结构蛋白与鲍曼不动杆菌相似,效应器曲目差异很大。有趣的是,医院内A.菌株的T6SS编码ophanVgrG蛋白,当过度表达时,会阻止系统的启动,提示T6SS存在新的调控机制。重要的是,虽然当细菌在营养丰富的培养基中生长时,T6SS不能提供优势,它可以使A.noconomialis在含有共存细菌的干燥表面中更好地存活。我们的结果表明,杀死共同存在的微生物可能会增加旨在通过靶向T6SS来降低不动杆菌细菌适应性的策略的有效性。
Pathogenic bacteria of the Acinetobacter genus pose a severe threat to human health worldwide due to their strong adaptability, tolerance, and antibiotic resistance. Most isolates of these bacteria harbor a type VI secretion system (T6SS) that allows them to outcompete co-residing microorganisms, but whether this system is involved in acquiring nutrients from preys remains less studied. In this study, we found that Ab25, a clinical isolate of Acinetobacter nosocomialis, utilizes a T6SS to kill taxonomically diverse microorganisms, including bacteria and fungi. The T6SS of Ab25 is constitutively expressed, and among the three predicted
effectors, T6e1, a member of the RHS effector family, contributes the most for its antimicrobial activity. T6e1 undergoes self-cleavage, and a short carboxyl fragment with nuclease activity is sufficient to kill target cells via T6SS injection. Interestingly, strain Ab25 encodes an orphan VgrG protein, which when overexpressed blocks the firing of its T6SS. In niches such as dry plastic surfaces, the T6SS promotes prey microorganism-dependent survival of Ab25. These results reveal that A. nosocomialis employs T6SSs that are highly diverse in their regulation and effector composition to gain a competitive advantage in environments with scarce nutrient supply and competing microbes.IMPORTANCEThe type VI secretion system (T6SS) plays an important role in bacterial adaptation to environmental challenges. Members of the Acinetobacter genus, particularly A. baumannii and A. nosocomialis, are notorious for their multidrug resistance and their ability to survive in harsh environments. In contrast to A. baumannii, whose T6SS has been well-studied, few research works have focused on A. nosocomialis. In this study, we found that an A. nosocomialis strain utilizes a contitutively active T6SS to kill diverse microorganisms, including bacteria and fungi. Although T6SS structural proteins of A. nosocomialis are similar to those of A. baumannii, the effector repertoire differs greatly. Interestingly, the T6SS of the A. nosocomialis strain codes for an ophan VgrG protein, which blocks the firing of the system when overexpressed, suggesting the existence of a new regulatory mechanism for the T6SS. Importantly, although the T6SS does not provide an advantage when the bacterium is grown in nutrient-rich medium, it allows A. nosocomialis to survive better in dry surfaces that contain co-existing bacteria. Our results suggest that killing of co-residing microorganisms may increase the effectiveness of strategies designed to reduce the fitness of Acinetobacter bacteria by targeting their T6SS.