Avirulent phenotype promotes <i>Bordetella pertussis</i> adaptation to the intramacrophage environment

<i>Bordetella pertussis</i>, the causative agent of whooping cough, is an extracellular, strictly human pathogen. However, it has been shown that <i>B. pertussis</i> cells can escape phagocytic killing and survive in macrophages upon internalization. Our time-resolved RNA-seq data suggest that <i>B. pertussis</i> efficiently adapts to the intramacrophage environment and responds to host bactericidal activities. We show that this adaptive response is multifaceted and, surprisingly, related to the BvgAS two-component system, a master regulator of virulence. Our results show that the expression of this regulatory circuit is downregulated upon internalization. Moreover, we demonstrate that the switch to the avirulent Bvg⁻ phase augments a very complex process based on the adjustment of central and energy metabolism, cell wall reinforcement, maintenance of appropriate redox and metal homeostasis, and repair of damaged macromolecules. Nevertheless, not all observed effects could be simply attributed to the transition to Bvg⁻ phase, suggesting that additional regulators are involved in the adaptation to the intramacrophage environment. Interestingly, a large number of genes required for the metabolism of sulphur were strongly modulated within macrophages. In particular, the mutant lacking two genes encoding cysteine dioxygenases displayed strongly attenuated cytotoxicity toward THP-1 cells. Collectively, our results suggest that intracellular <i>B. pertussis</i> cells have adopted the Bvg⁻ mode to acclimate to the intramacrophage environment and respond to antimicrobial activities elicited by THP-1 cells. Therefore, we hypothesize that the avirulent phase represents an authentic phenotype of internalized <i>B. pertussis</i> cells.

百日咳博德特氏菌（Bordetella pertussis）是百日咳的致病菌，属于胞外专性人类致病菌。但已有研究表明，百日咳博德特氏菌（B. pertussis）在被巨噬细胞内化后，能够逃逸吞噬杀伤并在巨噬细胞内存活。本研究的时间分辨率转录组测序（time-resolved RNA-seq）数据显示，百日咳博德特氏菌可高效适应巨噬细胞内环境，并对宿主的杀菌活性产生应答。我们证实，这种适应性应答具有多维度特征，且出乎意料地与毒力核心调控因子BvgAS双组分调控系统（BvgAS two-component system）相关。研究结果显示，该调控通路的表达在细菌内化后发生下调。此外，我们证明，向无毒力Bvg⁻表型的转变会增强一系列极为复杂的生物学过程，包括中枢与能量代谢调控、细胞壁加固、维持适宜的氧化还原与金属稳态，以及修复受损大分子物质。然而，并非所有观测到的效应都可简单归因于向Bvg⁻表型的转变，这提示存在额外的调控因子参与了巨噬细胞内环境的适应过程。值得关注的是，大量参与硫代谢的基因在巨噬细胞内受到显著调控。具体而言，缺失两个编码半胱氨酸双加氧酶基因的突变株，其对THP-1细胞的细胞毒性显著减弱。综上，本研究结果表明，胞内的百日咳博德特氏菌通过切换至Bvg⁻状态以适应巨噬细胞内环境，并应答THP-1细胞诱导产生的抗菌活性。因此，我们提出假说：无毒力表型是内化的百日咳博德特氏菌的真实表型。

搜集汇总

背景与挑战

背景概述

该数据集基于时间分辨RNA-seq数据，研究百日咳博德特氏菌在巨噬细胞内环境中的适应机制。研究发现，细菌通过下调BvgAS双组分系统转向无毒表型，从而调整代谢、强化细胞壁并应对宿主抗菌活动。这表明无毒表型可能是内部化细菌的真实表型，涉及硫代谢等关键基因的调控。