Laboratory of Bacteriology, Gene Regulation Section, Division of Intramural Research, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America.
Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019-UMR9017-CIIL-Centre d'Infection et d'Immunité de Lille, Lille, France.
PLoS Pathog. 2022 Mar 14;18(3):e1010370. doi: 10.1371/journal.ppat.1010370. eCollection 2022 Mar.
Borrelia species are amino acid auxotrophs that utilize di- and tri- peptides obtained through their oligopeptide transport system to supply amino acids for replicative growth during their enzootic cycles. However, Borrelia species from both the Lyme disease (LD) and relapsing fever (RF) groups harbor an amino acid transport and catabolism system, the Arginine Deiminase System (ADI), that could potentially augment intracellular L-arginine required for growth. RF spirochetes contain a "complete", four gene ADI (arcA, B, D, and C) while LD spirochetes harbor arcA, B, and sometimes D but lack arcC (encoding carbamate kinase). In this study, we evaluated the role of the ADI system in bacterial survival and virulence and discovered important differences in RF and LD ADIs. Both in vitro and in a murine model of infection, B. hermsii cells significantly reduced extracellular L-arginine levels and that reduction was dependent on arginine deiminase expression. Conversely, B. burgdorferi did not reduce the concentration of L-arginine during in vitro growth experiments nor during infection of the mammalian host, suggesting a fundamental difference in the ability to directly utilize L-arginine compared to B. hermsii. Further experiments using a panel of mutants generated in both B. burgdorferi and B. hermsii, identified important differences in growth characteristics and ADI transcription and protein expression. We also found that the ADI system plays a key role in blood and spleen colonization in RF spirochetes. In this study we have identified divergent metabolic strategies in two closely related human pathogens, that ultimately impacts the host-pathogen interface during infection.
伯氏疏螺旋体属物种是氨基酸营养缺陷型，它们利用二肽和三肽通过其寡肽转运系统获得氨基酸，以供应其在动物媒介循环中的复制生长所需的氨基酸。然而，莱姆病（LD）和回归热（RF）组的伯氏疏螺旋体属物种都具有氨基酸转运和分解代谢系统，即精氨酸脱亚氨酶系统（ADI），这可能会增加细胞内生长所需的 L-精氨酸。RF 螺旋体含有一个“完整”的四基因 ADI（arcA、B、D 和 C），而 LD 螺旋体含有 arcA、B，有时还有 D，但缺乏 arcC（编码氨基甲酰激酶）。在这项研究中，我们评估了 ADI 系统在细菌存活和毒力中的作用，发现了 RF 和 LD ADI 之间的重要差异。在体外和感染鼠模型中，B. hermsii 细胞显著降低了细胞外 L-精氨酸的水平，这种降低依赖于精氨酸脱亚氨酶的表达。相反，B. burgdorferi 在体外生长实验中或在感染哺乳动物宿主期间并未降低 L-精氨酸的浓度，这表明与 B. hermsii 相比，其直接利用 L-精氨酸的能力存在根本差异。在 B. burgdorferi 和 B. hermsii 中使用一组突变体进行的进一步实验确定了生长特性和 ADI 转录和蛋白表达方面的重要差异。我们还发现 ADI 系统在 RF 螺旋体的血液和脾脏定殖中起着关键作用。在这项研究中，我们确定了两种密切相关的人类病原体之间存在不同的代谢策略，这最终会影响感染期间的宿主-病原体界面。
