Table_1_MacAB-TolC Contributes to the Development of Acinetobacter baumannii Biofilm at the Solid–Liquid Interface.XLSX

Acinetobacter baumannii has emerged as one of the most problematic bacterial pathogens responsible for hospital-acquired and community infections worldwide. Besides its high capacity to acquire antibiotic resistance mechanisms, it also presents high adhesion abilities on inert and living surfaces leading to biofilm development. This lifestyle confers additional protection against various treatments and allows it to persist for long periods in various hospital niches. Due to their remarkable antimicrobial tolerance, A. baumannii biofilms are difficult to control and ultimately eradicate. Further insights into the mechanism of biofilm development will help to overcome this challenge and to develop novel antibiofilm strategies. To unravel critical determinants of this sessile lifestyle, the proteomic profiles of two A. baumannii strains (ATTC17978 and SDF) grown in planktonic stationary phase or in mature solid–liquid (S-L) biofilm were compared using a semiquantitative proteomic study. Of interest, among the 69 common proteins determinants accumulated in the two strains at the S-L interface, we sorted out the MacAB-TolC system. This tripartite efflux pump played a role in A. baumannii biofilm formation as demonstrated by using ΔmacAB-tolC deletion mutant. Complementary approaches allowed us to get an overview of the impact of macAB-tolC deletion in A. baumannii physiology. Indeed, this efflux pump appeared to be involved in the envelope stress response occurring in mature biofilm. It contributes to maintain wild type (WT) membrane rigidity and provides tolerance to high osmolarity conditions. In addition, this system is probably involved in the maintenance of iron and sulfur homeostasis. MacAB-TolC might help this pathogen face and adapt to deleterious conditions occurring in mature biofilms. Increasing our knowledge of A. baumannii biofilm formation will undoubtedly help us develop new therapeutic strategies to tackle this emerging threat to human health.

鲍曼不动杆菌（Acinetobacter baumannii）已成为全球范围内引发医院获得性与社区感染的最具挑战性的细菌性病原菌之一。该菌不仅具备高效获得抗生素耐药机制的能力，还拥有极强的黏附能力，可附着于惰性及活体表面并形成生物被膜。这种固着生活方式可为菌体提供额外的保护，抵御各类治疗手段，并使其能够在各类医院环境中长期存活。鉴于其显著的抗菌耐受性，鲍曼不动杆菌生物被膜难以有效管控并最终难以被彻底清除。深入解析生物被膜形成的关键机制，将有助于攻克这一难题并开发新型抗生物被膜策略。为阐明该固着生活方式的关键决定因素，本研究通过半定量蛋白质组学分析，对比了两株鲍曼不动杆菌（ATTC17978与SDF）在浮游静止期及成熟固液（S-L）界面生物被膜中的蛋白质组谱。值得关注的是，在两株菌于固液界面富集的69种共有蛋白决定因子中，我们筛选出了MacAB-TolC系统。该三组分外排泵在鲍曼不动杆菌生物被膜形成中发挥作用，这一点通过ΔmacAB-tolC缺失突变株的实验得到了验证。补充实验方法使我们得以全面解析macAB-tolC缺失对鲍曼不动杆菌生理的影响。研究发现，该外排泵参与成熟生物被膜中的包膜应激反应，可维持野生型（WT）膜刚性，并赋予菌体对高渗环境的耐受性。此外，该系统可能参与维持铁与硫的稳态。MacAB-TolC系统或可帮助该病原菌应对并适应成熟生物被膜内的有害环境。加深对鲍曼不动杆菌生物被膜形成机制的认知，无疑将助力开发新型治疗策略以应对这一对人类健康构成的新兴威胁。