Department of Microbiology and Immunology, The Brody School of Medicine at East Carolina University, Greenville, North Carolina, United States of America.
PLoS One. 2018 Oct 11;13(10):e0205638. doi: 10.1371/journal.pone.0205638. eCollection 2018.
For the opportunistic pathogen Acinetobacter baumannii, desiccation tolerance is thought to contribute significantly to the persistence of these bacteria in the healthcare environment. We investigated the ability of A. baumannii to survive rapid drying, and found that some strains exhibited a profoundly desiccation-resistant phenotype, characterized by the ability of a large proportion of cells to survive on a dry surface for an extended period of time. However, this phenotype was only displayed during the stationary phase of growth. Most interestingly, we found that drying resistance could be lost after extended cultivation in liquid medium. Genome sequencing of isolates that became drying-sensitive identified mutations in bfmR, which encodes a two-component response regulator that is important for A. baumannii virulence. Additionally, BfmR was necessary for the expression of stress-related proteins during stationary phase, and one of these, KatE, was important for long-term drying survival. These results suggested that BfmR may control stress responses, and we demonstrated that the ΔbfmR mutant was more sensitive to hydrogen peroxide, nutrient starvation, and increased osmolarity. We also found that cross-protection against drying could be stimulated by either starvation, which required BfmR, or increased osmolarity. These results imply that BfmR plays a role in controlling stress responses in A. baumannii which help protect cells during desiccation, and they provide a regulatory link between this organism's ability to persist in the environment and pathogenicity.
对于机会性病原体鲍曼不动杆菌，干燥耐受性被认为是这些细菌在医疗保健环境中持续存在的重要因素。我们研究了鲍曼不动杆菌在快速干燥下的存活能力，发现一些菌株表现出了极强的抗干燥表型，其特征是大量细胞能够在干燥表面上长时间存活。然而，这种表型仅在生长的静止期显示。最有趣的是，我们发现经过长时间在液体培养基中培养后，干燥抗性可以丧失。对干燥敏感的分离株进行基因组测序，发现了 bfmR 基因突变，该基因编码一种对鲍曼不动杆菌毒力很重要的双组分反应调节剂。此外，BfmR 是静止期表达应激相关蛋白所必需的，其中一种蛋白 KatE 对长期干燥存活很重要。这些结果表明 BfmR 可能控制应激反应，我们证明 ΔbfmR 突变体对过氧化氢、营养饥饿和渗透压增加更敏感。我们还发现，饥饿或渗透压增加都可以刺激对干燥的交叉保护，而饥饿需要 BfmR。这些结果表明，BfmR 在控制鲍曼不动杆菌的应激反应中发挥作用，有助于在干燥时保护细胞，为该生物体在环境中持续存在和致病性之间提供了一个调节联系。
